Investments in Fixed Maturity Securities (AFS Allowance for Credit Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	$ 22,238	$ 1,782
Expected credit losses on securities for which credit losses were not previously recorded	4,579	19,088
Expected credit losses on securities for which credit losses were previously recorded	10,573	1,925
Reduction due to disposals	(38)	(557)
Allowance for expected credit losses at September 30, 2020	37,352	22,238
Foreign Government
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	22,222	1,264
Expected credit losses on securities for which credit losses were not previously recorded	1,910	19,072
Expected credit losses on securities for which credit losses were previously recorded	8,534	2,438
Reduction due to disposals	(33)	(552)
Allowance for expected credit losses at September 30, 2020	32,633	22,222
Corporate
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	16	518
Expected credit losses on securities for which credit losses were not previously recorded	2,648	16
Expected credit losses on securities for which credit losses were previously recorded	2,042	(513)
Reduction due to disposals	(5)	(5)
Allowance for expected credit losses at September 30, 2020	4,701	16
Mortgage- Backed
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit losses at January 1, 2020	0
Expected credit losses on securities for which credit losses were not previously recorded	21
Expected credit losses on securities for which credit losses were previously recorded	(3)
Reduction due to disposals	0
Allowance for expected credit losses at September 30, 2020	$ 18	$ 0