| Cover Page Cover Page | Jul. 20, 2022 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Jul. 20, 2022 |
| Entity Registrant Name | NORTHERN TRUST CORP |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36609 |
| Entity Tax Identification Number | 36-2723087 |
| Entity Address, Address Line One | 50 South LaSalle Street |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60603 |
| City Area Code | 312 |
| Local Phone Number | 630-6000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000073124 |
| Amendment Flag | false |
| Entity Address, City or Town | Chicago, |
| Common Stock | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock, $1.66 2/3 Par Value |
| Trading Symbol | NTRS |
| Security Exchange Name | NASDAQ |
| Depositary Shares | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares, each representing 1/1,000th interest in a share of Series E Non-Cumulative Perpetual Preferred Stock |
| Trading Symbol | NTRSO |
| Security Exchange Name | NASDAQ |
