Mortgage Loans - Credit Quality Indicators - MF (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held for investment	$ 3,968,737	$ 3,659,247
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	59,007	72,014
One fiscal year before	80,197	69,337
Two fiscal years before	66,566	63,616
Three fiscal years before	57,666	53,523
Four fiscal years before	48,128	44,753
Prior	94,641	74,183
Total loans held for investment	406,205	377,426
Non-classified | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	58,986	71,977
One fiscal year before	79,602	68,296
Two fiscal years before	64,278	62,087
Three fiscal years before	55,552	50,907
Four fiscal years before	44,037	43,174
Prior	87,549	70,933
Total loans held for investment	390,004	367,374
Classified | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	21	37
One fiscal year before	595	1,041
Two fiscal years before	2,288	1,529
Three fiscal years before	2,114	2,616
Four fiscal years before	4,091	1,579
Prior	7,092	3,250
Total loans held for investment	16,201	10,052
Doubtful | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held for investment	$ 1	$ 1