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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% |  |

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