Investment Securities - Fair Value and Gross Unrealized Losses on Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair Value
Less than 12 months	$ 7,743	$ 1,336
12 months or more	952	604
Total	8,695	1,940
Unrealized Losses
Less than 12 months	(106)	(20)
12 months or more	(38)	(17)
Total	(144)	(37)
Agency mortgage-backed securities | Residential mortgage backed securities
Fair Value
Less than 12 months	935	426
12 months or more	161	1
Total	1,096	427
Unrealized Losses
Less than 12 months	(10)	(8)
12 months or more	(8)	0
Total	(18)	(8)
Agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	2,886	388
12 months or more	424	0
Total	3,310	388
Unrealized Losses
Less than 12 months	(49)	(5)
12 months or more	(20)	0
Total	(69)	(5)
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	1,052	2
12 months or more	0	0
Total	1,052	2
Unrealized Losses
Less than 12 months	(13)	0
12 months or more	0	0
Total	(13)	0
Asset-backed securities and other debt securities
Fair Value
Less than 12 months	2,870	520
12 months or more	367	603
Total	3,237	1,123
Unrealized Losses
Less than 12 months	(34)	(7)
12 months or more	(10)	(17)
Total	$ (44)	$ (24)