Mortgage Loans - TDRs with Sub Defaults (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) contract	Dec. 31, 2020 USD ($) contract	Dec. 31, 2019 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	9,243	15,586	17,851
Recorded investment troubled debt restructurings subsequent default | $	$ 1,510	$ 2,814	$ 2,758
Single-family
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	9,243	15,582	17,849
Recorded investment troubled debt restructurings subsequent default | $	$ 1,510	$ 2,798	$ 2,740
Single-family | 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	7,799	14,127	15,189
Recorded investment troubled debt restructurings subsequent default | $	$ 1,302	$ 2,578	$ 2,366
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	489	148	594
Recorded investment troubled debt restructurings subsequent default | $	$ 37	$ 10	$ 45
Single-family | Adjustable-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	33	16	91
Recorded investment troubled debt restructurings subsequent default | $	$ 5	$ 2	$ 14
Single-family | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	922	1,291	1,975
Recorded investment troubled debt restructurings subsequent default | $	$ 166	$ 208	$ 315
Multifamily
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contract	0	4	2
Recorded investment troubled debt restructurings subsequent default | $	$ 0	$ 16	$ 18