Mortgage Loans - Credit Quality Indicators - MF (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total mortgage loans	$ 3,851,488	$ 3,659,247
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2021	22,243	72,014
2020	81,664	69,337
2019	68,480	63,616
2018	62,222	53,523
2017	51,886	44,753
Prior	108,424	74,183
Total mortgage loans	394,919	377,426
Non-classified | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2021	22,243	71,977
2020	81,446	68,296
2019	67,290	62,087
2018	60,608	50,907
2017	49,030	43,174
Prior	102,818	70,933
Total mortgage loans	383,435	367,374
Classified | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	37
2020	218	1,041
2019	1,190	1,529
2018	1,614	2,616
2017	2,856	1,579
Prior	5,606	3,250
Total mortgage loans	11,484	10,052
Substandard or doubtful | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total mortgage loans	5	1
Single-family
Financing Receivable, Credit Quality Indicator [Line Items]
2021	657,211	1,253,449
2020	1,229,217	367,647
2019	267,707	178,798
2018	129,544	226,092
2017	169,689	272,831
Prior	995,515	972,993
Total mortgage loans	$ 3,448,883	$ 3,271,810