Investments in Fixed Maturity Securities (HTM Allowance for Credit Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses, beginning of period	$ 453	$ 948	$ 798	$ 0
Cumulative effect adjustment resulting from changes in accounting principles	396	871	396	871
Provision for expected credit losses	(57)	(77)	(402)	802
Allowance for expected credit losses, end of period	$ 396	$ 871	396	871
Cumulative effect adjustment resulting from changes in accounting principles
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses, beginning of period			$ 0	$ 69
Cumulative effect adjustment resulting from changes in accounting principles