Investments - Available for Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Loaned securities	$ 112,139	$ 103,996
Total fixed-maturities, available for sale, Amortized Cost	5,587,261	5,367,729
Total fixed-maturities available for sale, Fair Value	5,017,711	5,517,078
Fixed-maturities available for sale \| U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	174,138	221,407
Gross Unrealized Gains	206	1,719
Gross Unrealized Losses	(28,902)	(1,396)
Fair Value	145,442	221,730
Fixed-maturities available for sale \| State and municipal obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	164,325	162,964
Gross Unrealized Gains	0	14,694
Gross Unrealized Losses	(21,939)	(401)
Fair Value	142,386	177,257
Fixed-maturities available for sale \| Corporate bonds and notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,886,905	2,867,063
Gross Unrealized Gains	1,403	133,665
Gross Unrealized Losses	(350,537)	(24,886)
Fair Value	2,537,771	2,975,842
Fixed-maturities available for sale \| RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,025,795	697,581
Gross Unrealized Gains	1,163	14,313
Gross Unrealized Losses	(98,559)	(6,777)
Fair Value	928,399	705,117
Fixed-maturities available for sale \| CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	645,890	690,827
Gross Unrealized Gains	13	21,444
Gross Unrealized Losses	(52,546)	(3,068)
Fair Value	593,357	709,203
Fixed-maturities available for sale \| CLO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	518,677	529,906
Gross Unrealized Gains	0	1,032
Gross Unrealized Losses	(20,485)	(898)
Fair Value	498,192	530,040
Fixed-maturities available for sale \| Other ABS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	168,033	210,657
Gross Unrealized Gains	69	1,142
Gross Unrealized Losses	(6,743)	(612)
Fair Value	161,359	211,187
Fixed-maturities available for sale \| Foreign government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,118	5,109
Gross Unrealized Gains	0	187
Gross Unrealized Losses	(143)	0
Fair Value	4,975	5,296
Fixed-maturities available for sale \| Mortgage insurance-linked notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	54,578	45,384
Gross Unrealized Gains	80	1,633
Gross Unrealized Losses	(1,639)	0
Fair Value	53,019	47,017
Fixed-maturities available for sale \| Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,643,459	5,430,898
Total fixed-maturities, available for sale, Amortized Cost	5,587,261	5,367,729
Gross Unrealized Gains	2,934	189,829
Gross Unrealized Losses	(581,493)	(38,038)
Fair Value	5,064,900	5,582,689
Total fixed-maturities available for sale, Fair Value	5,017,711	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]
Loaned securities	56,198	63,169
Fixed-maturities available for sale \| Loaned securities
Debt Securities, Available-for-sale [Line Items]
Loaned securities	47,200
Fixed-maturities available for sale \| Loaned securities \| Total fixed-maturities available for sale
Debt Securities, Available-for-sale [Line Items]
Loaned securities	$ 47,189	$ 65,611

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Available-For-Sale Securities, Debt Securities, Including Loaned Securities

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Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, Before Tax, Including Loaned Securities

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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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