Investments - Schedule of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, at fair value	$ 2,705,131	$ 2,702,567
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	2,789,517	2,621,388
Available-for-sale debt securities gross unrealized gain	22,692	95,045
Available-for-sale debt securities, gross unrealized loss	(107,078)	(13,866)
Available-for-sale debt securities, at fair value	2,705,131	2,702,567
Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	43,733	85,246
Available-for-sale debt securities gross unrealized gain		1
Available-for-sale debt securities, gross unrealized loss	(33)	(4)
Available-for-sale debt securities, at fair value	43,700	85,243
Fixed-Maturity Securities and Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	2,833,250	2,706,634
Available-for-sale debt securities gross unrealized gain	22,692	95,046
Available-for-sale debt securities, gross unrealized loss	(107,111)	(13,870)
Available-for-sale debt securities, at fair value	2,748,831	2,787,810
U.S. Government and Agencies [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	32,347	32,292
Available-for-sale debt securities gross unrealized gain	91	187
Available-for-sale debt securities, gross unrealized loss	(527)	(79)
Available-for-sale debt securities, at fair value	31,911	32,400
Foreign Government [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	151,735	147,288
Available-for-sale debt securities gross unrealized gain	1,824	6,283
Available-for-sale debt securities, gross unrealized loss	(4,568)	(595)
Available-for-sale debt securities, at fair value	148,991	152,976
States and Political Subdivisions [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	147,757	147,455
Available-for-sale debt securities gross unrealized gain	883	6,326
Available-for-sale debt securities, gross unrealized loss	(6,925)	(254)
Available-for-sale debt securities, at fair value	141,715	153,527
Corporates [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	1,688,749	1,649,334
Available-for-sale debt securities gross unrealized gain	17,658	72,418
Available-for-sale debt securities, gross unrealized loss	(59,696)	(8,068)
Available-for-sale debt securities, at fair value	1,646,711	1,713,684
Residential Mortgage-backed Securities [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	470,130	373,753
Available-for-sale debt securities gross unrealized gain	1,427	5,108
Available-for-sale debt securities, gross unrealized loss	(24,433)	(3,230)
Available-for-sale debt securities, at fair value	447,124	375,631
Commercial Mortgage-backed Securities [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	147,425	142,631
Available-for-sale debt securities gross unrealized gain	362	3,314
Available-for-sale debt securities, gross unrealized loss	(4,922)	(420)
Available-for-sale debt securities, at fair value	142,865	145,525
Other Asset-backed Securities [Member] \| Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost basis	151,374	128,635
Available-for-sale debt securities gross unrealized gain	447	1,409
Available-for-sale debt securities, gross unrealized loss	(6,007)	(1,220)
Available-for-sale debt securities, at fair value	$ 145,814	$ 128,824

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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