Investment Securities - Schedule of Investments within the Available for Sale Portfolio that had Unrealized Losses (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Fair Value
Less than 12 months	$ 883	$ 1,614
12 months or longer	5,645	5,855
Total fair value	6,528	7,469
Unrealized Losses
Less than 12 months	(2)	(18)
12 months or longer	(748)	(1,017)
Total unrealized losses	(750)	(1,035)
Government agency issued MBS
Fair Value
Less than 12 months	146	663
12 months or longer	2,885	2,992
Total fair value	3,031	3,655
Unrealized Losses
Less than 12 months	(1)	(9)
12 months or longer	(363)	(513)
Total unrealized losses	(364)	(522)
Government agency issued CMO
Fair Value
Less than 12 months	407	675
12 months or longer	1,720	1,744
Total fair value	2,127	2,419
Unrealized Losses
Less than 12 months	0	(2)
12 months or longer	(239)	(310)
Total unrealized losses	(239)	(312)
Other U.S. government agencies
Fair Value
Less than 12 months	300	210
12 months or longer	801	863
Total fair value	1,101	1,073
Unrealized Losses
Less than 12 months	(1)	(6)
12 months or longer	(116)	(155)
Total unrealized losses	(117)	(161)
States and municipalities
Fair Value
Less than 12 months	30	66
12 months or longer	239	256
Total fair value	269	322
Unrealized Losses
Less than 12 months	0	(1)
12 months or longer	(30)	(39)
Total unrealized losses	$ (30)	$ (40)