Mortgage Loans - Credit Quality Indicators - MF (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total mortgage loans	$ 4,050,517,000,000	$ 3,968,737,000,000
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2022	7,429,000,000	59,007,000,000
2021	67,070,000,000	80,197,000,000
2020	79,303,000,000	66,566,000,000
2019	65,454,000,000	57,666,000,000
2018	56,231,000,000	48,128,000,000
Prior	136,980,000,000	94,641,000,000
Total mortgage loans	412,467,000,000	406,205,000,000
Non-classified | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2022	7,429,000,000	58,986,000,000
2021	66,972,000,000	79,602,000,000
2020	78,830,000,000	64,278,000,000
2019	62,884,000,000	55,552,000,000
2018	53,920,000,000	44,037,000,000
Prior	124,949,000,000	87,549,000,000
Total mortgage loans	394,984,000,000	390,004,000,000
Classified | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2022	0	21,000,000
2021	98,000,000	595,000,000
2020	473,000,000	2,288,000,000
2019	2,570,000,000	2,114,000,000
2018	2,311,000,000	4,091,000,000
Prior	12,031,000,000	7,092,000,000
Total mortgage loans	17,483,000,000	16,201,000,000
Substandard or doubtful | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total mortgage loans	$ 0	$ 1,000,000