Investments - Schedule of Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 1,656,021	$ 839,581
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(92,016)	(10,309)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	115,054	70,909
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(15,095)	(3,561)
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	1,612,321	764,334
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(91,983)	(10,305)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	115,054	70,909
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(15,095)	(3,561)
Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	43,700	75,247
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(33)	(4)
U.S. Government and Agencies [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	25,427	24,928
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(433)	(45)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	1,489	1,557
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(94)	(34)
U.S. Government and Agencies [Member] | Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	34,955	34,967
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(28)
Foreign Government [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	69,053	18,894
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(3,178)	(384)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	7,638	3,335
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(1,390)	(211)
Foreign Government [Member] | Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	4,996	4,995
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(3)
States and Political Subdivisions [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	106,659	15,909
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(6,862)	(254)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	977
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(63)
States and Political Subdivisions [Member] | Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	1,399	11,394
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(1)	(1)
Corporates [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	805,228	341,963
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(48,221)	(5,035)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	83,518	59,414
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(11,475)	(3,033)
Corporates [Member] | Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	2,350	23,891
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(1)	(3)
Residential Mortgage-backed Securities [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	374,688	234,911
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(23,033)	(3,131)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	14,561	2,707
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(1,400)	(99)
Commercial Mortgage-backed Securities [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	112,306	47,220
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(4,644)	(419)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	3,175	117
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(278)	(1)
Other Asset-backed Securities [Member] | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	118,960	80,509
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(5,612)	(1,037)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	3,696	3,779
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (395)	$ (183)