Derivative Instruments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative offsetting [Abstract]
Derivative assets subject to master netting agreements		$ 122,300	$ 138,800
Derivative liabilities subject to master netting agreements		53,900	93,000
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(32,390)	179,675	$ 119,741
Not Designated as Hedging Instrument
Derivative [Line Items]
Asset derivatives - fair value		127,121	177,383
Liability derivatives - fair value		(54,224)	(108,705)
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(32,390)	179,675	119,741
Not Designated as Hedging Instrument | Futures contracts
Derivative [Line Items]
Net derivatives - notional value	[1],[2]	2,826,564	3,099,796
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(15,262)	114,987	114,123
Not Designated as Hedging Instrument | Futures contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	34,999	11,046
Not Designated as Hedging Instrument | Futures contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(9,808)	(4,496)
Not Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Net derivatives - notional value	[1],[2]	915,962	1,656,729
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(39,755)	49,974	(9,499)
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	7,734	52,716
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	(11,390)	(6,202)
Not Designated as Hedging Instrument | TBAs
Derivative [Line Items]
Net derivatives - notional value	[1]	11,227	0
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		(233)	1,129	463
Not Designated as Hedging Instrument | TBAs | Fixed maturities available for sale, at fair value
Derivative [Line Items]
Asset derivatives - fair value		11,227	0
Liability derivatives - fair value		0	0
Not Designated as Hedging Instrument | Other
Derivative [Line Items]
Net derivatives - notional value	[1],[2]	3,736,773	5,763,919
Net realized gains (losses) on derivative instruments
Net realized gains (losses) on derivative instruments		22,860	13,585	$ 14,654
Not Designated as Hedging Instrument | Other | Other assets
Derivative [Line Items]
Asset derivatives - fair value	[2]	73,161	113,621
Not Designated as Hedging Instrument | Other | Other liabilities
Derivative [Line Items]
Liability derivatives - fair value	[2]	$ (33,026)	$ (98,007)

[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.’