Derivative Instruments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Derivative offsetting [Abstract]
Derivative assets subject to master netting agreements		$ 147,400	$ 122,300
Derivative liabilities subject to master netting agreements		73,200	53,900
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(75,023)	(32,390)	$ 179,675
Not Designated as Hedging Instrument
Derivative [Line Items]
Asset derivatives - fair value		148,301	127,121
Liability derivatives - fair value		(75,961)	(54,224)
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(75,023)	(32,390)	179,675
Not Designated as Hedging Instrument | Futures contracts
Derivative [Line Items]
Net derivatives - notional value	[1]	3,138,446	2,826,564
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(86,634)	(15,262)	114,987
Not Designated as Hedging Instrument | Futures contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	50,629	34,999
Not Designated as Hedging Instrument | Futures contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(16,963)	(9,808)
Not Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Net derivatives - notional value	[1]	1,136,126	915,962
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		6,144	(39,755)	49,974
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	38,891	7,734
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(35,446)	(11,390)
Not Designated as Hedging Instrument | TBAs
Derivative [Line Items]
Net derivatives - notional value	[1]		11,227
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(51)	(233)	1,129
Not Designated as Hedging Instrument | TBAs | Fixed maturities available for sale, at fair value
Derivative [Line Items]
Asset derivatives - fair value	[2]		11,227
Liability derivatives - fair value	[2]		0
Not Designated as Hedging Instrument | Other
Derivative [Line Items]
Net derivatives - notional value	[1]	3,591,793	3,736,773
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		5,518	22,860	$ 13,585
Not Designated as Hedging Instrument | Other | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	58,781	73,161
Not Designated as Hedging Instrument | Other | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	$ (23,552)	$ (33,026)

[1] Represents the absolute notional value of all outstanding contracts, consisting of long and short positions.

[2] The fair value of asset derivatives are included in ‘other assets’ and the fair value of liability derivatives are included in ‘other liabilities.’