Long-Term Debt - Schedule of Long Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Long-term finance leases and equipment financing	$ 89	$ 67
Total long-term debt	25,143	23,272
Fair Value Hedges
Debt Instrument [Line Items]
Long-term debt	$ 3	220
Parent Company and Non-banking Subsidiaries | Senior notes | 4.536%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.536%
Long-term debt	$ 1,346	0
Parent Company and Non-banking Subsidiaries | Senior notes | 4.33%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.33%
Long-term debt	$ 1,208	1,189
Parent Company and Non-banking Subsidiaries | Senior notes | 5.272%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.272%
Long-term debt	$ 1,204	1,203
Parent Company and Non-banking Subsidiaries | Senior notes | 4.993%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.993%
Long-term debt	$ 1,004	993
Parent Company and Non-banking Subsidiaries | Senior notes | 4.834%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.834%
Long-term debt	$ 1,002	0
Parent Company and Non-banking Subsidiaries | Senior notes | 2.4%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	2.40%
Long-term debt	$ 777	784
Parent Company and Non-banking Subsidiaries | Senior notes | 2.65%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	2.65%
Long-term debt	$ 745	728
Parent Company and Non-banking Subsidiaries | Senior notes | 4.729%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.729%
Long-term debt	$ 647	0
Parent Company and Non-banking Subsidiaries | Senior notes | Floating-rate, Senior notes due August 3, 2026
Debt Instrument [Line Items]
Long-term debt	300	299
Parent Company and Non-banking Subsidiaries | Senior notes | Floating-rate, Senior notes Due October 22, 2027
Debt Instrument [Line Items]
Long-term debt	299	299
Parent Company and Non-banking Subsidiaries | Senior notes | Floating-rate, Senior notes 3
Debt Instrument [Line Items]
Long-term debt	$ 299	0
Parent Company and Non-banking Subsidiaries | Senior notes | 7.35%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	7.35%
Long-term debt	$ 150	150
Parent Company and Non-banking Subsidiaries | Senior notes | 3.55%, Senior notes
Debt Instrument [Line Items]
Interest rate on debt	3.55%
Long-term debt	$ 0	1,285
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 5.684%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.684%
Long-term debt	$ 1,009	986
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.53%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.53%
Long-term debt	$ 1,007	989
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 5.159%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.159%
Long-term debt	$ 996	995
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.784%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.784%
Long-term debt	$ 973	0
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.675,% Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.675%
Long-term debt	$ 813	789
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 5.146%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.146%
Long-term debt	$ 746	0
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.821%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.821%
Long-term debt	$ 728	702
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.543%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.543%
Long-term debt	$ 699	0
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.164%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.164%
Long-term debt	$ 695	665
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 2.203%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	2.203%
Long-term debt	$ 634	619
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.141%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.141%
Long-term debt	$ 536	535
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 5.82%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.82%
Long-term debt	$ 503	495
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 3.152%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	3.152%
Long-term debt	$ 499	498
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.421%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.421%
Long-term debt	$ 498	498
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 1.684%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	1.684%
Long-term debt	$ 498	497
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 2.623%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	2.623%
Long-term debt	$ 490	465
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 5.104%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.104%
Long-term debt	$ 0	999
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 4.857%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	4.857%
Long-term debt	$ 0	499
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 5.751%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	5.751%
Long-term debt	$ 0	498
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 2.901%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	2.901%
Long-term debt	$ 0	497
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 1.746%, Fixed-to-floating rate senior notes
Debt Instrument [Line Items]
Interest rate on debt	1.746%
Long-term debt	$ 0	299
Parent Company and Non-banking Subsidiaries | Senior Subordinated Notes [Member] | 2.2%, Senior subordinated notes
Debt Instrument [Line Items]
Interest rate on debt	2.20%
Long-term debt	$ 846	845
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 3.031%, Fixed-to-floating rate senior subordinated notes
Debt Instrument [Line Items]
Interest rate on debt	3.031%
Long-term debt	$ 518	523
Parent Company and Non-banking Subsidiaries | Fixed-to-floating rate senior notes | 6.123%, Fixed-to-floating rate senior subordinated notes
Debt Instrument [Line Items]
Interest rate on debt	6.123%
Long-term debt	$ 507	492
Parent Company and Non-banking Subsidiaries | Junior Subordinated Debt [Member] | Floating-rate, Junior subordinated debentures Due June 15, 2047
Debt Instrument [Line Items]
Long-term debt	500	500
Parent Company and Non-banking Subsidiaries | Junior Subordinated Debt [Member] | Floating-rate, Junior subordinated debentures due May 15, 2028
Debt Instrument [Line Items]
Long-term debt	100	100
State Street Bank
Debt Instrument [Line Items]
Long-term finance leases and equipment financing	$ 122	116
State Street Bank | Senior notes | 4.594% Senior Notes Due 2026
Debt Instrument [Line Items]
Interest rate on debt	4.594%
Long-term debt	$ 1,148	1,146
State Street Bank | Senior notes | 4.782% Senior Notes Due 2029
Debt Instrument [Line Items]
Interest rate on debt	4.782%
Long-term debt	$ 797	796
State Street Bank | Senior notes | Floating Rate Senior Notes Due 2026
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 299