Securities - Available for Sale Securities (Unrealized Loss Position) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Held-to-maturity securities:
Temporarily impaired securities, fair value, less than 12 months	$ 36,256	$ 29,680
Temporarily impaired securities, gross unrealized losses, less than 12 months	2,001	568
Temporarily impaired securities, fair value, 12 months or longer	9,968	5,511
Temporarily impaired securities, gross unrealized losses, 12 months or longer	1,104	316
Temporarily impaired securities, fair value	46,224	35,191
Temporarily impaired securities, gross unrealized losses	3,105	884
U.S. Treasury, agencies and corporations
Securities available for sale:
Fair value, less than 12 months	8,800	9,078
Gross unrealized losses, less than 12 months	394	98
Fair value, 12 months or longer	589	243
Gross unrealized losses, 12 months or longer	22	3
Fair value	9,389	9,321
Gross unrealized losses	416	101
Held-to-maturity securities:
Fair value, less than 12 months	0
Gross unrealized losses, less than 12 months	0
Fair value, 12 months or longer	0
Gross unrealized losses, 12 months or longer	0
Fair value	0
Gross unrealized losses	0
State And Political Subdivisions
Held-to-maturity securities:
Fair value, less than 12 months	0
Gross unrealized losses, less than 12 months	0
Fair value, 12 months or longer	0
Gross unrealized losses, 12 months or longer	0
Fair value	0
Gross unrealized losses	0
Agency residential collateralized mortgage obligations
Securities available for sale:
Fair value, less than 12 months	16,751	12,603
Gross unrealized losses, less than 12 months	1,138	315
Fair value, 12 months or longer	3,460	1,255
Gross unrealized losses, 12 months or longer	480	95
Fair value	20,211	13,858
Gross unrealized losses	1,618	410
Held-to-maturity securities:
Fair value, less than 12 months	1,905	96
Gross unrealized losses, less than 12 months	67	0
Fair value, 12 months or longer	0	0
Gross unrealized losses, 12 months or longer	0	0
Fair value	1,905	96
Gross unrealized losses	67	0
Agency residential mortgage-backed securities
Held-to-maturity securities:
Fair value, less than 12 months	150
Gross unrealized losses, less than 12 months	3
Fair value, 12 months or longer	0
Gross unrealized losses, 12 months or longer	0
Fair value	150
Gross unrealized losses	3
Agency residential mortgage-backed securities | Maximum
Held-to-maturity securities:
Gross unrealized losses		1
Agency commercial mortgage-backed securities
Securities available for sale:
Fair value, less than 12 months	1,973	1,645
Gross unrealized losses, less than 12 months	58	75
Fair value, 12 months or longer	4,808	3,834
Gross unrealized losses, 12 months or longer	482	215
Fair value	6,781	5,479
Gross unrealized losses	540	290
Held-to-maturity securities:
Fair value, less than 12 months	1,393
Gross unrealized losses, less than 12 months	32
Fair value, 12 months or longer	0
Gross unrealized losses, 12 months or longer	0
Fair value	1,393
Gross unrealized losses	32
Asset-backed securities (c)
Held-to-maturity securities:
Fair value, less than 12 months	2,081	2,450
Gross unrealized losses, less than 12 months	89	31
Fair value, 12 months or longer	1	1
Gross unrealized losses, 12 months or longer	0	0
Fair value	2,082	2,451
Gross unrealized losses	89	31
Asset-backed securities (c) | Maximum
Held-to-maturity securities:
Gross unrealized losses	1
Other securities
Held-to-maturity securities:
Fair value, less than 12 months	7	15
Gross unrealized losses, less than 12 months	0	0
Fair value, 12 months or longer	3	0
Gross unrealized losses, 12 months or longer	0	0
Fair value	10	15
Gross unrealized losses	0	0
Mortgage-backed securities | Agency residential mortgage-backed securities
Securities available for sale:
Fair value, less than 12 months	3,196	3,793
Gross unrealized losses, less than 12 months	220	49
Fair value, 12 months or longer	1,107	178
Gross unrealized losses, 12 months or longer	120	3
Fair value	4,303	3,971
Gross unrealized losses	$ 340	$ 52