Mortgage Loans - Loan Restructuring - Aging Analysis (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 37,039
Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	23,603
30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,906
60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	2,207
Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	17,624
Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	21,737
Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,866
Single-family
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 36,743
Single-family | Minimum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due	90 days	90 days
Single-family | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 23,336
Single-family | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,906
Single-family | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	2,207
Single-family | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	17,381
Single-family | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	21,494
Single-family | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,842
Single-family | 20- and 30-year or more, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	33,954
Single-family | 20- and 30-year or more, amortizing fixed-rate | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	21,520
Single-family | 20- and 30-year or more, amortizing fixed-rate | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,765
Single-family | 20- and 30-year or more, amortizing fixed-rate | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	2,048
Single-family | 20- and 30-year or more, amortizing fixed-rate | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	16,040
Single-family | 20- and 30-year or more, amortizing fixed-rate | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	19,853
Single-family | 20- and 30-year or more, amortizing fixed-rate | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,667
Single-family | 15-year or less, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,437
Single-family | 15-year or less, amortizing fixed-rate | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,042
Single-family | 15-year or less, amortizing fixed-rate | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	98
Single-family | 15-year or less, amortizing fixed-rate | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	108
Single-family | 15-year or less, amortizing fixed-rate | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	715
Single-family | 15-year or less, amortizing fixed-rate | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	921
Single-family | 15-year or less, amortizing fixed-rate | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	121
Single-family | Adjustable-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	213
Single-family | Adjustable-rate | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	151
Single-family | Adjustable-rate | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	8
Single-family | Adjustable-rate | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	9
Single-family | Adjustable-rate | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	119
Single-family | Adjustable-rate | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	136
Single-family | Adjustable-rate | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	15
Single-family | Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,139
Single-family | Other | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	623
Single-family | Other | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	35
Single-family | Other | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	42
Single-family | Other | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	507
Single-family | Other | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	584
Single-family | Other | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	39
Multifamily
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 296
Multifamily | Minimum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due	60 days
Multifamily | Maximum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due	89 days
Multifamily | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 267
Multifamily | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	0
Multifamily | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	243
Multifamily | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	243
Multifamily | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 24