Fair Value of Financial Instruments - Carrying Value of Commercial Mortgage Loans and Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total amortized cost	$ 47,042	$ 47,201
Allowance for mortgage loan losses	(66)	(71)
Mortgage loans, net	46,976	47,130
Total mortgage loans | Mortgage Loans by Region
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 47,042	$ 47,201
Percent of Total	100.00%	100.00%
Total mortgage loans | Mortgage Loans by Region | East North Central
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 3,245	$ 3,245
Percent of Total	6.90%	6.90%
Total mortgage loans | Mortgage Loans by Region | Southern Atlantic
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 9,533	$ 9,578
Percent of Total	20.30%	20.30%
Total mortgage loans | Mortgage Loans by Region | East South Central
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 7,968	$ 8,028
Percent of Total	16.90%	17.00%
Total mortgage loans | Mortgage Loans by Region | New England
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 6,588	$ 6,588
Percent of Total	14.00%	14.00%
Total mortgage loans | Mortgage Loans by Region | Middle Atlantic
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 14,740	$ 14,789
Percent of Total	31.40%	31.30%
Total mortgage loans | Mortgage Loans by Region | Mountain
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 2,227	$ 2,227
Percent of Total	4.70%	4.70%
Total mortgage loans | Mortgage Loans by Region | West North Central
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 2,741	$ 2,746
Percent of Total	5.80%	5.80%
Total mortgage loans | Mortgage Loans by Property Type
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 47,042	$ 47,201
Percent of Total	100.00%	100.00%
Total mortgage loans | Mortgage Loans by Property Type | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 16,956	$ 16,986
Percent of Total	36.00%	36.00%
Total mortgage loans | Mortgage Loans by Property Type | Office
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 11,496	$ 11,571
Percent of Total	24.50%	24.50%
Total mortgage loans | Mortgage Loans by Property Type | Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 10,108	$ 10,124
Percent of Total	21.50%	21.50%
Total mortgage loans | Mortgage Loans by Property Type | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 2,227	$ 2,227
Percent of Total	4.70%	4.70%
Total mortgage loans | Mortgage Loans by Property Type | Mixed use/Other
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net	$ 6,255	$ 6,293
Percent of Total	13.30%	13.30%
Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Total amortized cost	$ 29,811	$ 29,924
65%-75%
Financing Receivable, Credit Quality Indicator [Line Items]
Total amortized cost	$ 17,231	$ 17,277