Mortgage Loans - TDRs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) contract	Dec. 31, 2020 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Average term extension of a single-family modified loan	145 months	163 months
Average interest rate reduction of a single-family modified loan	0.57%	0.37%
Number of loans troubled debt restructurings activity | contract	12,620	35,049
Restructured loans, amortized cost | $	$ 1,883	$ 5,665
Single-family
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	12,620	35,049
Restructured loans, amortized cost | $	$ 1,883	$ 5,665
Single-family | 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	10,815	29,938
Restructured loans, amortized cost | $	$ 1,717	$ 5,125
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	1,165	2,956
Restructured loans, amortized cost | $	$ 93	$ 257
Single-family | Adjustable-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	116	467
Restructured loans, amortized cost | $	$ 17	$ 72
Single-family | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	524	1,688
Restructured loans, amortized cost | $	$ 56	$ 211
Multifamily
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	0	0
Restructured loans, amortized cost | $	$ 0	$ 0