| Document and Entity Information | 12 Months Ended |
| Dec. 31, 2022 | |
| Cover [Abstract] | |
| Document Type | DEF 14A |
| Amendment Flag | false |
| Entity Registrant Name | ATI Physical Therapy, Inc. |
| Entity Central Index Key | 0001815849 |
| Pay vs Performance Disclosure - USD ($) | 4 Months Ended | 5 Months Ended | 7 Months Ended | 8 Months Ended | 12 Months Ended | |
| Apr. 27, 2022 | Dec. 31, 2021 | Aug. 07, 2021 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021 | |
| Pay vs Performance Disclosure [Table] | ||||||
| Pay vs Performance [Table Text Block] | Pay Versus Performance Year Summary Compensation Table Total for PEO #1 (1) Summary Compensation Table Total for PEO #2 (2) Compensation Actually Paid to PEO #1 (3) Compensation Actually Paid to PEO #2 (3) Average Summary Compensation Table Total for Non-PEO NEOs (4) Average Compensation Actually Paid to Non-PEO NEOs (5) Value of Initial Fixed $100 Investment Based On: Net Income (Loss) Adj. EBITDA ($ in thousands) Net Revenue ($ in thousands) Total Shareholder Return (6) Peer Group Total Shareholder Return (a) (b) (bb) (c) (cc) (d) (e) (f) (g) (h) (i) (i) 2022 2,637,822 537,231 1,227,258 483,793 786,975 580,440 3 108 (493,047) 6,712 635,671 2021 2,943,057 1,145,602 4,448,222 1,153,662 901,810 910,686 34 112 (782,028) 39,771 627,871 (1) Represents the total compensation paid to Sharon Vitti, our current Principal Executive Officer (“PEO” #1) since April 28, 2022. The dollar amounts reported in column (b) for 2022 are the amounts of total compensation reported for Ms. Vitti in the “Total” column of the Summary Compensation Table (“SCT”). The dollar amounts reported for PEO #1 in column (b) for 2021 are the amounts of total compensation reported for former Chief Executive Officer, Labeed Diab, who stepped down effective August 7, 2021. (2) Represents the total compensation paid to John Larsen, our prior Principal Executive Officer (“PEO” #2). The dollar amounts in column (bb) are the amounts of total compensation reported for Mr. Larsen in the “Total” column of the Summary Compensation Table (“SCT”). John Larsen became ATI’s Executive Chairman on August 9, 2021, and served in that capacity through April 27, 2022. (3) The dollar amounts reported in column (c) represent the amount of “compensation actually paid” (“CAP”) to the PEO computed in accordance with Item 402(v) of Regulation S-K, adjustments were made to the PEO’s total compensation for each year to determine the CAP. (4) The dollar amounts reported in column (d) represent the average of the amounts for the Company's NEOs as a group (excluding the PEO) in the “Total'' column of the SCT. For 2022, the Non-PEO NEOs were Joseph Jordan, Ray Wahl, Augustus Oakes, Joseph Zavalishin, Erik Kantz, and Eimile Tansey. For 2021, the Non-PEO NEOs were Joseph Jordan, Ray Wahl, Diana Chafey, Joseph Zavalishin, and Augustus Oakes. (5) The dollar amount reported in column (e) represents the average amount of “compensation actually paid” to the Non-PEO NEOs as a group, as computed in accordance with Item 402(v) of Regulation S-K, adjustments were made to average total compensation for the Non-PEO NEOs as a group for each year to determine the compensation actually paid. (6) TSR calculation start date is 6/17/21 (rather than 1/1/21) since that is the date our Class A common stock began trading on the NYSE following the Business Combination / de-SPAC. | |||||
| Company Selected Measure Name | Adj. EBITDA | |||||
| Named Executive Officers, Footnote [Text Block] | (4) The dollar amounts reported in column (d) represent the average of the amounts for the Company's NEOs as a group (excluding the PEO) in the “Total'' column of the SCT. For 2022, the Non-PEO NEOs were Joseph Jordan, Ray Wahl, Augustus Oakes, Joseph Zavalishin, Erik Kantz, and Eimile Tansey. For 2021, the Non-PEO NEOs were Joseph Jordan, Ray Wahl, Diana Chafey, Joseph Zavalishin, and Augustus Oakes. | |||||
| Adjustment To PEO Compensation, Footnote [Text Block] | (3) The dollar amounts reported in column (c) represent the amount of “compensation actually paid” (“CAP”) to the PEO computed in accordance with Item 402(v) of Regulation S-K, adjustments were made to the PEO’s total compensation for each year to determine the CAP. PEO #1 SCT Total TO CAP Reconciliation Year Reported Summary Compensation Table Total for PEO ($) Minus: Reported Summary Compensation Table Value of Equity Awards ($) Plus: Equity Award Adjustments ($) Plus: Reported Change in Pension Value Deferred Compensation Earnings in Summary Compensation Table ($) Plus: Pension Benefit Adjustments ($) Compensation Actually Paid to PEO ($) 2022 2,637,822 1,701,063 290,499 — — 1,227,258 2021 2,943,057 — — 1,505,165 (1) — 4,448,222 (1) This relates to severance to our Former Chief Executive Officer, Labeed Diab, who stepped down effective August 7, 2021. PEO #2 SCT Total TO CAP Reconciliation Year Reported Summary Compensation Table Total for PEO ($) Minus: Reported Summary Compensation Table Value of Equity Awards ($) Plus: Equity Award Adjustments ($) Plus: Reported Change in Pension Value Deferred Compensation Earnings in Summary Compensation Table ($) Plus: Pension Benefit Adjustments ($) Compensation Actually Paid to PEO ($) 2022 537,231 128,696 75,258 — — 483,793 2021 1,145,602 590,085 598,145 — — 1,153,662 Equity Award Adjustments PEO #1 Year Year End Fair Value of Awards Granted in the Year ($) Year over Year Change in Fair Value of Outstanding and Unvested Awards ($) Fair Value as of Vesting Date of Awards Granted and Vested in the Year ($) Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year ($) Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year Total Equity Award Adjustments ($) 2022 290,499 — — — — — 290,499 2021 — — — — — — — Equity Award Adjustments PEO #2 Year Year End Fair Value of Awards Granted in the Year ($) Year over Year Change in Fair Value of Outstanding and Unvested Awards ($) Fair Value as of Vesting Date of Awards Granted and Vested in the Year ($) Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year ($) Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year Total Equity Award Adjustments ($) 2022 19,648 24,419 — 31,191 — — 75,258 2021 598,145 — — — — — 598,145 | |||||
| Non-PEO NEO Average Total Compensation Amount | $ 786,975 | $ 901,810 | ||||
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 580,440 | 910,686 | ||||
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | (5) The dollar amount reported in column (e) represents the average amount of “compensation actually paid” to the Non-PEO NEOs as a group, as computed in accordance with Item 402(v) of Regulation S-K, adjustments were made to average total compensation for the Non-PEO NEOs as a group for each year to determine the compensation actually paid. Average Non-PEO SCT Total TO CAP Reconciliation Year Reported Summary Compensation Table Total for PEO ($) Minus: Reported Summary Compensation Table Value of Equity Awards ($) Plus: Equity Award Adjustments ($) Plus: Reported Change in Pension Value Deferred Compensation Earnings in Summary Compensation Table ($) Plus: Pension Benefit Adjustments ($) Compensation Actually Paid to PEO ($) 2022 786,975 310,420 107,216 (3,332) — 580,440 2021 901,810 369,679 374,094 4,462 — 910,686 Equity Award Adjustments Year Year End Fair Value of Awards Granted in the Year ($) Year over Year Change in Fair Value of Outstanding and Unvested Awards ($) Fair Value as of Vesting Date of Awards Granted and Vested in the Year ($) Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year ($) Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year Total Equity Award Adjustments ($) 2022 51,065 46,866 — 9,286 — — 107,216 2021 374,094 — — — — — 374,094 | |||||
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | Relationship between Compensation Actually Paid disclosed in the Pay Versus Performance table, and other table elements. Compensation Actually Paid (“CAP”) to Mrs. Vitti, Mr. Diab, and Mr. Larsen and cumulative total shareholder return were both higher in 2021 relative to 2022. The increase in CAP to PEO for Mr. Diab was largely related to severance. The average NEO CAP decreased over the reported period, primarily because of the change in NEOs in 2022 compared to 2021. The decrease in ATI Physical Therapy’s stock price largely contributed to the decreased PEO CAP, and also drove the decrease in ATI’s Total Shareholder Return (“TSR”) in 2022 compared to 2021. At the end of the two-year period, ATI’s cumulative TSR ended lower than the cumulative TSR of ATI’s 2022 Peer Group. The TSR decreased over the two-year period, the average NEO CAP decreased for the reasons noted above. | |||||
| Compensation Actually Paid vs. Net Income [Text Block] | Relationship between Compensation Actually Paid disclosed in the Pay Versus Performance table, and other table elements. ATI’s Adjusted EBITDA and Net Income decreased from 2022 compared to 2021 and was directionally aligned with PEO CAP for the reported period. Average NEO CAP decreased for the reasons noted above. | |||||
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | Relationship between Compensation Actually Paid disclosed in the Pay Versus Performance table, and other table elements. ATI’s Adjusted EBITDA and Net Income decreased from 2022 compared to 2021 and was directionally aligned with PEO CAP for the reported period. Average NEO CAP decreased for the reasons noted above. | |||||
| Total Shareholder Return Vs Peer Group [Text Block] | Relationship between Compensation Actually Paid disclosed in the Pay Versus Performance table, and other table elements. Compensation Actually Paid (“CAP”) to Mrs. Vitti, Mr. Diab, and Mr. Larsen and cumulative total shareholder return were both higher in 2021 relative to 2022. The increase in CAP to PEO for Mr. Diab was largely related to severance. The average NEO CAP decreased over the reported period, primarily because of the change in NEOs in 2022 compared to 2021. The decrease in ATI Physical Therapy’s stock price largely contributed to the decreased PEO CAP, and also drove the decrease in ATI’s Total Shareholder Return (“TSR”) in 2022 compared to 2021. At the end of the two-year period, ATI’s cumulative TSR ended lower than the cumulative TSR of ATI’s 2022 Peer Group. The TSR decreased over the two-year period, the average NEO CAP decreased for the reasons noted above. | |||||
| Tabular List [Table Text Block] | Tabular List of ATI Physical Therapy’s most important metrics that link Compensation Actually Paid to the PEO and other NEOs. We consider the list below to be ATI’s most important metrics that link compensation paid to our Named Executive Officers, as they are the key metrics that determine the payout of ATI’s Annual Incentive Plan. • Adjusted EBITDA • Net Revenue • Net Income | |||||
| Total Shareholder Return Amount | $ 3 | 34 | ||||
| Peer Group Total Shareholder Return Amount | 108 | 112 | ||||
| Net Income (Loss) | $ (493,047,000) | $ (782,028,000) | ||||
| Company Selected Measure Amount | 6,712,000 | 39,771,000 | ||||
| PEO Name | John Larsen | John Larsen | Labeed Diab | Sharon Vitti | ||
| Measure [Axis]: 1 | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Measure Name | Adjusted EBITDA | |||||
| Measure [Axis]: 2 | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Other Performance Measure Amount | 635,671,000 | 627,871,000 | ||||
| Measure Name | Net Revenue | |||||
| Measure [Axis]: 3 | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Measure Name | Net Income | |||||
| Sharon Vitti [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| PEO Total Compensation Amount | $ 2,637,822 | |||||
| PEO Actually Paid Compensation Amount | 1,227,258 | |||||
| John Larsen [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| PEO Total Compensation Amount | 537,231 | $ 1,145,602 | ||||
| PEO Actually Paid Compensation Amount | 483,793 | 1,153,662 | ||||
| Labeed Diab [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| PEO Total Compensation Amount | 2,943,057 | |||||
| PEO Actually Paid Compensation Amount | 4,448,222 | |||||
| PEO [Member] | Sharon Vitti [Member] | Value of Equity Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | (1,701,063) | |||||
| PEO [Member] | Sharon Vitti [Member] | Equity Award Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 290,499 | |||||
| PEO [Member] | Sharon Vitti [Member] | Year End Fair Value of Awards Granted in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 290,499 | |||||
| PEO [Member] | Sharon Vitti [Member] | Year over Year Change in Fair Value of Outstanding and Unvested Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Sharon Vitti [Member] | Fair Value as of Vesting Date of Awards Granted and Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Sharon Vitti [Member] | Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Sharon Vitti [Member] | Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Sharon Vitti [Member] | Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Sharon Vitti [Member] | Change in Pension Value Deferred Compensation Earnings [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Sharon Vitti [Member] | Pension Benefit Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | John Larsen [Member] | Value of Equity Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | (128,696) | (590,085) | ||||
| PEO [Member] | John Larsen [Member] | Equity Award Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 75,258 | 598,145 | ||||
| PEO [Member] | John Larsen [Member] | Year End Fair Value of Awards Granted in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 19,648 | 598,145 | ||||
| PEO [Member] | John Larsen [Member] | Year over Year Change in Fair Value of Outstanding and Unvested Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 24,419 | 0 | ||||
| PEO [Member] | John Larsen [Member] | Fair Value as of Vesting Date of Awards Granted and Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| PEO [Member] | John Larsen [Member] | Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 31,191 | 0 | ||||
| PEO [Member] | John Larsen [Member] | Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| PEO [Member] | John Larsen [Member] | Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| PEO [Member] | John Larsen [Member] | Change in Pension Value Deferred Compensation Earnings [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| PEO [Member] | John Larsen [Member] | Pension Benefit Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| PEO [Member] | Labeed Diab [Member] | Value of Equity Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Equity Award Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Year End Fair Value of Awards Granted in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Year over Year Change in Fair Value of Outstanding and Unvested Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Fair Value as of Vesting Date of Awards Granted and Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| PEO [Member] | Labeed Diab [Member] | Change in Pension Value Deferred Compensation Earnings [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 1,505,165 | |||||
| PEO [Member] | Labeed Diab [Member] | Pension Benefit Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | |||||
| Non-PEO NEO [Member] | Value of Equity Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | (310,420) | (369,679) | ||||
| Non-PEO NEO [Member] | Equity Award Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 107,216 | 374,094 | ||||
| Non-PEO NEO [Member] | Year End Fair Value of Awards Granted in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 51,065 | 374,094 | ||||
| Non-PEO NEO [Member] | Year over Year Change in Fair Value of Outstanding and Unvested Awards [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 46,866 | 0 | ||||
| Non-PEO NEO [Member] | Fair Value as of Vesting Date of Awards Granted and Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| Non-PEO NEO [Member] | Year over Year Change in Fair Value of Awards Granted in Prior Years that Vested in the Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 9,286 | 0 | ||||
| Non-PEO NEO [Member] | Fair Value as of Prior Year End of Equity Awards Granted in Prior Years that Failed to Vest in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| Non-PEO NEO [Member] | Dollar Value of Dividends / Earnings Paid on Equity Awards in the Covered Year [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | 0 | 0 | ||||
| Non-PEO NEO [Member] | Change in Pension Value Deferred Compensation Earnings [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | (3,332) | 4,462 | ||||
| Non-PEO NEO [Member] | Pension Benefit Adjustments [Member] | ||||||
| Pay vs Performance Disclosure [Table] | ||||||
| Adjustment to Compensation Amount | $ 0 | $ 0 | ||||
