Investments (Fixed Income Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Fixed Income Securities [Line Items]
Due in one year or less fair value, AFS	$ 322,189
Due after one year through five years fair value, AFS	2,826,402
Due after five years through 10 years fair value, AFS	2,410,981
Due after 10 years fair value, AFS	912,528
Total AFS fixed income securities, Fair Value	6,472,100	$ 6,709,976
Due in one year or less carrying value, HTM	6,577
Due after one year through five years carrying value, HTM	4,955
Due after five years through 10 years carrying value, HTM	21,476
Due after 10 years carrying value, HTM	0
Fixed income securities, held-to-maturity, net of allowance for credit losses	33,008	28,785
Due in one year or less fair value, HTM	6,595
Due after one year through five years fair value, HTM	4,907
Due after five years through 10 years fair value, HTM	19,980
Due after 10 years fair value, HTM	0
Total HTM fixed income securities, Fair Value	$ 31,482	$ 29,460