Securities - Details of Securities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
SECURITIES AVAILABLE FOR SALE
Amortized Cost	$ 45,893	$ 26,810
Gross Unrealized Gains	324	804
Gross Unrealized Losses	853	58
Securities available for sale	45,364	27,556
HELD-TO-MATURITY SECURITIES
Amortized Cost	7,539	7,595
Gross Unrealized Gains	157	428
Gross Unrealized Losses	31	0
Fair Value	7,665	8,023
Available-for-sale securities, accrued interest	59	42
Held-to-maturity securities, accrued interest	15	15
U.S. Treasury, agencies and corporations
SECURITIES AVAILABLE FOR SALE
Amortized Cost	9,573	1,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	101	0
Securities available for sale	9,472	1,000
Agency residential collateralized mortgage obligations
SECURITIES AVAILABLE FOR SALE
Amortized Cost	21,430	14,001
Gross Unrealized Gains	99	297
Gross Unrealized Losses	410	25
Securities available for sale	21,119	14,273
HELD-TO-MATURITY SECURITIES
Amortized Cost	2,196	3,775
Gross Unrealized Gains	33	124
Gross Unrealized Losses	0	0
Fair Value	2,229	3,899
Agency residential mortgage-backed securities
SECURITIES AVAILABLE FOR SALE
Amortized Cost	5,137	2,094
Gross Unrealized Gains	37	70
Gross Unrealized Losses	52	0
Securities available for sale	5,122	2,164
HELD-TO-MATURITY SECURITIES
Amortized Cost	164	271
Gross Unrealized Gains	6	14
Gross Unrealized Losses	0	0
Fair Value	170	285
Asset-backed securities(b)
HELD-TO-MATURITY SECURITIES
Amortized Cost	2,485	19
Gross Unrealized Gains	0	0
Gross Unrealized Losses	31	0
Fair Value	2,454	19
Securities related to purchase of senior notes	2,500
Other securities
SECURITIES AVAILABLE FOR SALE
Amortized Cost	0	8
Gross Unrealized Gains	0	5
Gross Unrealized Losses	0	0
Securities available for sale	0	13
HELD-TO-MATURITY SECURITIES
Amortized Cost	16	15
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	16	15
Mortgage-backed securities \| Agency commercial mortgage-backed securities
SECURITIES AVAILABLE FOR SALE
Amortized Cost	9,753	9,707
Gross Unrealized Gains	188	432
Gross Unrealized Losses	290	33
Securities available for sale	9,651	10,106
HELD-TO-MATURITY SECURITIES
Amortized Cost	2,678	3,515
Gross Unrealized Gains	118	290
Gross Unrealized Losses	0	0
Fair Value	$ 2,796	$ 3,805

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