Investments - Available for Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Less: loaned securities	$ 79,073	$ 103,996
Total fixed-maturities available for sale	5,643,884	5,367,729
Total fixed-maturities available for sale	5,228,744	5,517,078
Fixed-maturities available for sale \| U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	198,819	221,407
Gross Unrealized Gains	35	1,719
Gross Unrealized Losses	(18,350)	(1,396)
Fair Value	180,504	221,730
Fixed-maturities available for sale \| State and municipal obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	166,024	162,964
Gross Unrealized Gains	1,006	14,694
Gross Unrealized Losses	(12,050)	(401)
Fair Value	154,980	177,257
Fixed-maturities available for sale \| Corporate bonds and notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,042,032	2,867,063
Gross Unrealized Gains	1,838	133,665
Gross Unrealized Losses	(271,736)	(24,886)
Fair Value	2,772,134	2,975,842
Fixed-maturities available for sale \| RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	840,157	697,581
Gross Unrealized Gains	146	14,313
Gross Unrealized Losses	(63,917)	(6,777)
Fair Value	776,386	705,117
Fixed-maturities available for sale \| CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	649,521	690,827
Gross Unrealized Gains	89	21,444
Gross Unrealized Losses	(31,007)	(3,068)
Fair Value	618,603	709,203
Fixed-maturities available for sale \| CLO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	520,479	529,906
Gross Unrealized Gains	0	1,032
Gross Unrealized Losses	(17,665)	(898)
Fair Value	502,814	530,040
Fixed-maturities available for sale \| Other ABS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	184,182	210,657
Gross Unrealized Gains	42	1,142
Gross Unrealized Losses	(4,202)	(612)
Fair Value	180,022	211,187
Fixed-maturities available for sale \| Foreign government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,113	5,109
Gross Unrealized Gains	0	187
Gross Unrealized Losses	(64)	0
Fair Value	5,049	5,296
Fixed-maturities available for sale \| Mortgage insurance-linked notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	53,685	45,384
Gross Unrealized Gains	0	1,633
Gross Unrealized Losses	(1,085)	0
Fair Value	52,600	47,017
Fixed-maturities available for sale \| Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,660,012	5,430,898
Total fixed-maturities available for sale	5,643,884	5,367,729
Gross Unrealized Gains	3,156	189,829
Gross Unrealized Losses	(420,076)	(38,038)
Fair Value	5,243,092	5,582,689
Total fixed-maturities available for sale	5,228,744	5,517,078
Fixed-maturities available for sale \| Loaned securities, amortized cost \| Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Less: loaned securities	16,128	63,169
Fixed-maturities available for sale \| Loaned securities, fair value \| Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Less: loaned securities	$ 14,348	$ 65,611

Available-for-sale Debt Securities, Amortized Cost Basis, Including Loaned Securities

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Available-for-sale Securities, Debt Securities, Including Loaned Securities

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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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Amount, before tax, of unrealized loss 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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Amortized cost of 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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Amount of 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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Amount of asset associated with securities loaned to entities in exchange for collateral.

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