| Document and Entity Information - USD ($) | 12 Months Ended | ||
| Sep. 30, 2021 | Nov. 03, 2021 | Mar. 31, 2021 | |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| Document Annual Report | true | ||
| Document Period End Date | Sep. 30, 2021 | ||
| Document Transition Report | false | ||
| Entity File Number | 001-32833 | ||
| Entity Registrant Name | TransDigm Group Incorporated | ||
| Entity Central Index Key | 0001260221 | ||
| Current Fiscal Year End Date | --09-30 | ||
| Document Fiscal Year Focus | 2021 | ||
| Document Fiscal Period Focus | FY | ||
| Amendment Flag | false | ||
| Entity Incorporation, State or Country Code | DE | ||
| Entity Tax Identification Number | 41-2101738 | ||
| Entity Address, Address Line One | 1301 East 9th Street, | ||
| Entity Address, Address Line Two | Suite 3000, | ||
| Entity Address, City or Town | Cleveland, | ||
| Entity Address, State or Province | OH | ||
| Entity Address, Postal Zip Code | 44114 | ||
| City Area Code | 216 | ||
| Local Phone Number | 706-2960 | ||
| Title of 12(b) Security | Common Stock, $0.01 par value | ||
| Trading Symbol | TDG | ||
| Security Exchange Name | NYSE | ||
| Entity Well-known Seasoned Issuer | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Small Business | false | ||
| Entity Emerging Growth Company | false | ||
| ICFR Auditor Attestation Flag | true | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 32,940,645,808 | ||
| Entity Common Stock, Shares Outstanding | 55,248,901 | ||
| Documents Incorporated by Reference | None |
