Investments in Fixed Maturity Securities (AFS Allowance for Credit Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses, beginning of period	$ 22,238	$ 1,782
Cumulative effect adjustment resulting from changes in accounting principles	26,153	20,009
Expected credit losses on securities for which credit losses were not previously recorded	484	19,006
Expected credit losses (gains) on securities for which credit losses were previously recorded	3,431	(774)
Reduction due to disposals	0	(5)
Allowance for expected credit losses, end of period	26,153	20,009
Foreign government
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses, beginning of period	22,222	1,264
Cumulative effect adjustment resulting from changes in accounting principles	26,153	19,993
Expected credit losses on securities for which credit losses were not previously recorded	484	18,990
Expected credit losses (gains) on securities for which credit losses were previously recorded	3,447	(261)
Reduction due to disposals	0	0
Allowance for expected credit losses, end of period	26,153	19,993
Corporate
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses, beginning of period	16	518
Cumulative effect adjustment resulting from changes in accounting principles	0	16
Expected credit losses on securities for which credit losses were not previously recorded	0	16
Expected credit losses (gains) on securities for which credit losses were previously recorded	(16)	(513)
Reduction due to disposals	0	(5)
Allowance for expected credit losses, end of period	$ 0	$ 16