Investments - Commercial Mortgage Loan Participations, Internal Credit Assessment (Details) $ in Thousands	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Less allowance for credit losses on individual loans	$ (1,002)
Commercial mortgage participations
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	24
2020	$ 20,176
2019	29,951
2018	52,520
2017	61,460
Total commercial mortgage loans	164,107	$ 137,692
Less allowance for credit losses on the investment pool	(2,503)
Carrying value, net of valuation allowance	$ 160,602	$ 137,692
Commercial mortgage participations \| Low
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	17
2020	$ 20,176
2019	14,757
2018	33,132
2017	61,460
Total commercial mortgage loans	$ 129,525
Commercial mortgage participations \| Medium
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	4
2020	$ 0
2019	10,640
2018	7,796
2017	0
Total commercial mortgage loans	$ 18,436
Commercial mortgage participations \| High
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	3
2020	$ 0
2019	4,554
2018	11,592
2017	0
Total commercial mortgage loans	$ 16,146

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