Goodwill and Other Intangible Assets - Gross Carrying Amount, Accumulated Amortization and Net Carrying Amount of Other Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 4,034	$ 4,060
Accumulated amortization	(3,162)	(3,125)
Net carrying amount	872	935	$ 1,089
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	2,813	2,831
Accumulated amortization	(2,167)	(2,144)
Net carrying amount	646	687
Technology
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	404	405
Accumulated amortization	(302)	(293)
Net carrying amount	102	112
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	699	703
Accumulated amortization	(601)	(597)
Net carrying amount	98	106
Other
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	118	121
Accumulated amortization	(92)	(91)
Net carrying amount	$ 26	$ 30