Investments in Fixed Maturity Securities (AFS Allowance for Credit Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	$ 1,782	$ 0
Cumulative effect adjustment resulting from changes in accounting principles	22,238	1,782
Expected credit losses on securities for which credit losses were not previously recorded	19,088	19,648
Expected credit losses on securities for which credit losses were previously recorded	1,925	(3,468)
Reduction due to disposals	(557)	(50,043)
Allowance for expected credit losses at September 30, 2020	22,238	1,782
Cumulative Effect, Period Of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	0	35,645
Cumulative effect adjustment resulting from changes in accounting principles		0
Allowance for expected credit losses at September 30, 2020		0
Foreign government
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	1,264	0
Cumulative effect adjustment resulting from changes in accounting principles	22,222	1,264
Expected credit losses on securities for which credit losses were not previously recorded	19,072	12,590
Expected credit losses on securities for which credit losses were previously recorded	2,438	373
Reduction due to disposals	(552)	(47,344)
Allowance for expected credit losses at September 30, 2020	22,222	1,264
Foreign government | Cumulative Effect, Period Of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	0	35,645
Cumulative effect adjustment resulting from changes in accounting principles		0
Allowance for expected credit losses at September 30, 2020		0
Corporate
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	518	0
Cumulative effect adjustment resulting from changes in accounting principles	16	518
Expected credit losses on securities for which credit losses were not previously recorded	16	7,058
Expected credit losses on securities for which credit losses were previously recorded	(513)	(3,841)
Reduction due to disposals	(5)	(2,699)
Allowance for expected credit losses at September 30, 2020	16	518
Corporate | Cumulative Effect, Period Of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	$ 0	0
Cumulative effect adjustment resulting from changes in accounting principles		0
Allowance for expected credit losses at September 30, 2020		$ 0