Investments - Available for Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Less: loaned securities	$ 148,098	$ 203,693
Total fixed maturities, available-for-sale, Amortized Cost	5,648,303	5,599,111
Total fixed-maturities available for sale, Fair Value	5,176,521	5,188,228
Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Total	5,758,323	5,734,767
Total fixed maturities, available-for-sale, Amortized Cost	5,648,303	5,599,111
Gross Unrealized Gains	16,751	24,174
Gross Unrealized Losses	(494,833)	(443,531)
Fair Value	5,280,241	5,315,410
Total fixed-maturities available for sale, Fair Value	5,176,521	5,188,228
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Total	166,275	171,194
Gross Unrealized Gains	0	93
Gross Unrealized Losses	(31,581)	(26,891)
Fair Value	134,694	144,396
State and municipal obligations
Debt Securities, Available-for-sale [Line Items]
Total	169,734	158,539
Gross Unrealized Gains	87	283
Gross Unrealized Losses	(16,850)	(16,037)
Fair Value	152,971	142,785
Corporate bonds and notes
Debt Securities, Available-for-sale [Line Items]
Total	2,804,815	2,876,175
Gross Unrealized Gains	5,287	12,286
Gross Unrealized Losses	(297,211)	(259,177)
Fair Value	2,512,891	2,629,284
RMBS
Debt Securities, Available-for-sale [Line Items]
Total	1,157,427	1,089,919
Gross Unrealized Gains	8,153	8,250
Gross Unrealized Losses	(104,775)	(84,098)
Fair Value	1,060,805	1,014,071
CMBS
Debt Securities, Available-for-sale [Line Items]
Total	532,968	605,029
Gross Unrealized Gains	33	51
Gross Unrealized Losses	(37,386)	(46,697)
Fair Value	495,615	558,383
CLO
Debt Securities, Available-for-sale [Line Items]
Total	517,651	494,339
Gross Unrealized Gains	310	63
Gross Unrealized Losses	(2,622)	(6,553)
Fair Value	515,339	487,849
Other ABS
Debt Securities, Available-for-sale [Line Items]
Total	363,736	286,988
Gross Unrealized Gains	843	1,608
Gross Unrealized Losses	(4,408)	(4,037)
Fair Value	360,171	284,559
Foreign government and agency securities
Debt Securities, Available-for-sale [Line Items]
Total		5,128
Gross Unrealized Gains		0
Gross Unrealized Losses		(41)
Fair Value		5,087
Mortgage insurance-linked notes
Debt Securities, Available-for-sale [Line Items]
Total	45,717	47,456
Gross Unrealized Gains	2,038	1,540
Gross Unrealized Losses	0	0
Fair Value	47,755	48,996
Loaned securities, amortized cost | Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Less: loaned securities	110,020	135,656
Loaned securities, fair value | Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Less: loaned securities	$ 103,720	$ 127,182