Investments in Fixed Maturity Securities (HTM Allowance for Credit Loss) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	$ 0
Held-to-maturity, allowance for credit loss	798
Provision for expected credit losses	729
Allowance for expected credit losses at September 30, 2020	798
Cumulative Effect, Period Of Adoption, Adjustment
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	69
Held-to-maturity, allowance for credit loss	$ 69