Commitments and Guarantees - Contractual Amounts of Credit-Related Off-Balance Sheet Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Unfunded credit facilities	$ 35,590	$ 35,697
Indemnified securities financing	407,558	371,968
Standby letters of credit	$ 461	$ 569

Aggregate Fair Value Of Indemnified Securities On Loan

No definition available.

Name:	stt_AggregateFairValueOfIndemnifiedSecuritiesOnLoan
Namespace Prefix:	stt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant