Mortgage Loans - TDRs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Average term extension of a single-family modified loan	145 months
Average interest rate reduction of a single-family modified loan	0.57%
Number of loans troubled debt restructurings activity | contract	12,620
Restructured loans, amortized cost | $	$ 1,883
Single-family
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	12,620
Restructured loans, amortized cost | $	$ 1,883
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
Restructured loans, amortized cost | $	$ 1,717
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
Restructured loans, amortized cost | $	$ 93
Single-family | Adjustable-rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	116
Restructured loans, amortized cost | $	$ 17
Single-family | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	524
Restructured loans, amortized cost | $	$ 56
Multifamily
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings activity | contract	0
Restructured loans, amortized cost | $	$ 0