Investment Securities - Investment Available for Sale (Details) - USD ($)			12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 94,871,000,000	$ 97,569,000,000	$ 94,871,000,000	$ 97,569,000,000
Allowance for Credit Losses	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Gross Unrealized Gains	1,387,000,000	2,997,000,000	1,387,000,000	2,997,000,000
Gross Unrealized Losses	(996,000,000)	(120,000,000)	(996,000,000)	(120,000,000)
Fair Value	95,261,000,000	100,445,000,000	95,261,000,000	100,445,000,000
Accrued interest receivable			207,000,000	230,000,000
Security Owned and Pledged as Collateral, Fair Value	20,800,000,000	16,500,000,000	20,800,000,000	16,500,000,000
Securities Received as Collateral	1,000,000	1,000,000	1,000,000	1,000,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,419,000,000	9,302,000,000	9,419,000,000	9,302,000,000
Allowance for Credit Losses	0	0	0	0
Gross Unrealized Gains	23,000,000	16,000,000	23,000,000	16,000,000
Gross Unrealized Losses	0	0	0	0
Fair Value	9,442,000,000	9,318,000,000	9,442,000,000	9,318,000,000
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	72,593,000,000	73,248,000,000	72,593,000,000	73,248,000,000
Allowance for Credit Losses	0	0	0	0
Gross Unrealized Gains	958,000,000	2,326,000,000	958,000,000	2,326,000,000
Gross Unrealized Losses	(931,000,000)	(108,000,000)	(931,000,000)	(108,000,000)
Fair Value	72,620,000,000	75,466,000,000	72,620,000,000	75,466,000,000
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	792,000,000	1,035,000,000	792,000,000	1,035,000,000
Allowance for Credit Losses	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Gross Unrealized Gains	205,000,000	204,000,000	205,000,000	204,000,000
Gross Unrealized Losses	0	(1,000,000)	0	(1,000,000)
Fair Value	996,000,000	1,237,000,000	996,000,000	1,237,000,000
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	73,385,000,000	74,283,000,000	73,385,000,000	74,283,000,000
Allowance for Credit Losses	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Gross Unrealized Gains	1,163,000,000	2,530,000,000	1,163,000,000	2,530,000,000
Gross Unrealized Losses	(931,000,000)	(109,000,000)	(931,000,000)	(109,000,000)
Fair Value	73,616,000,000	76,703,000,000	73,616,000,000	76,703,000,000
CMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,237,000,000	11,298,000,000	9,237,000,000	11,298,000,000
Allowance for Credit Losses	0	0	0	0
Gross Unrealized Gains	195,000,000	448,000,000	195,000,000	448,000,000
Gross Unrealized Losses	(63,000,000)	(11,000,000)	(63,000,000)	(11,000,000)
Fair Value	9,369,000,000	11,735,000,000	9,369,000,000	11,735,000,000
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,830,000,000	2,686,000,000	2,830,000,000	2,686,000,000
Allowance for Credit Losses	0	0	0	0
Gross Unrealized Gains	6,000,000	3,000,000	6,000,000	3,000,000
Gross Unrealized Losses	(2,000,000)	0	(2,000,000)	0
Fair Value	2,834,000,000	2,689,000,000	2,834,000,000	2,689,000,000
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 2,000,000,000	$ 1,800,000,000	$ 2,000,000,000	$ 1,800,000,000
US Treasury and Agency securities | Available-for-sale securities | Government Contracts Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Percentage of portfolio	96.00%	96.00%