| Cover page Entity information (Details) | Oct. 21, 2019 |
| Entity Information [Line Items] | |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Document Type | 8-K |
| Document Period End Date | Oct. 21, 2019 |
| Amendment Flag | false |
| Entity Emerging Growth Company | false |
| City Area Code | 617 |
| Entity Address, Address Line One | One Lincoln Street |
| Entity Incorporation, State or Country Code | MA |
| Entity File Number | 001-07511 |
| Entity Address, City or Town | Boston |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02111 |
| Entity Tax Identification Number | 04-2456637 |
| Local Phone Number | 786-3000 |
| Entity Central Index Key | 0000093751 |
| Entity Registrant Name | State Street Corp |
| Written Communications | false |
| Cover page Entity listings (Details) | Oct. 21, 2019 |
| Series E Preferred Stock, Depository Share [Member] | |
| Class of Stock [Line Items] | |
| Title of 12(b) Security | Non-Cumulative Perpetual Preferred Stock, Series E, without par value per share |
| Trading Symbol | STT.PRE |
| Security Exchange Name | NYSE |
| Series G Preferred Stock, Depository Share [Member] | |
| Class of Stock [Line Items] | |
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series G, without par value per share |
| Trading Symbol | STT.PRG |
| Security Exchange Name | NYSE |
| Series D Preferred Stock, Depository Share [Member] | |
| Class of Stock [Line Items] | |
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series D, without par value per share |
| Trading Symbol | STT.PRD |
| Security Exchange Name | NYSE |
| Series C Preferred Stock, Depository Share [Member] | |
| Class of Stock [Line Items] | |
| Title of 12(b) Security | Non-Cumulative Perpetual Preferred Stock, Series C, without par value per share |
| Trading Symbol | STT.PRC |
| Security Exchange Name | NYSE |
| Common Stock [Member] | |
| Class of Stock [Line Items] | |
| Title of 12(b) Security | Common stock, $1 par value per share |
| Trading Symbol | STT |
| Security Exchange Name | NYSE |
