Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,970,459	$ 6,397,658
Fair Value	5,400,982	6,587,581
Assets held by insurance regulatory requirements	12,200	13,400
Assets held in trust for the benefit of contractual counterparties	165,000	189,800
FHLB advance, collateral pledged		167,200
Total fixed income securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,970,459	6,397,658
Gross Unrealized Gains	1,907	218,390
Gross Unrealized Losses	(571,384)	(28,467)
Fair Value	5,400,982	6,587,581
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	180,941	133,990
Gross Unrealized Gains	25	285
Gross Unrealized Losses	(10,294)	(868)
Fair Value	170,672	133,407
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,414,505	2,408,688
Gross Unrealized Gains	1,700	133,361
Gross Unrealized Losses	(265,167)	(7,396)
Fair Value	2,151,038	2,534,653
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,393,106	2,704,586
Gross Unrealized Gains	148	75,172
Gross Unrealized Losses	(227,409)	(13,776)
Fair Value	2,165,845	2,765,982
ABS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	134,309	150,888
Gross Unrealized Gains	5	830
Gross Unrealized Losses	(5,819)	(1,008)
Fair Value	128,495	150,710
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	230,997	309,991
Gross Unrealized Gains	15	2,397
Gross Unrealized Losses	(28,372)	(3,278)
Fair Value	202,640	309,110
CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	266,711	315,330
Gross Unrealized Gains	14	5,736
Gross Unrealized Losses	(21,080)	(1,936)
Fair Value	245,645	319,130
CLOs
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	337,827	360,436
Gross Unrealized Gains	0	609
Gross Unrealized Losses	(12,329)	(106)
Fair Value	325,498	360,939
Foreign government debt
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,486	13,749
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(914)	(99)
Fair Value	3,572	$ 13,650
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,577
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 7,577

Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

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