Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	$ 6,325,797
Other comprehensive loss	(86,080)	$ (357,175)
End of period	6,430,284
Net realized and unrealized gains (losses) on investments	51,759	(143,285)
Income (loss) before income taxes	296,068	(6,468)
Tax effect	(64,352)	2,942
Net income (loss) before noncontrolling interests	231,716	(3,526)
Total change in unrealized investment losses	(113,735)	(332,850)
Net change in period	4,050	(98,194)
Other comprehensive income (loss), pre-tax	(109,685)	(431,044)
Other comprehensive income (loss), tax effect	23,605	73,869
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(62,172)	(257,299)
Other comprehensive income (loss) before reclassifications	(94,941)	(396,725)
Amounts reclassified from AOCI	8,861	39,550
Other comprehensive loss	(86,080)	(357,175)
Unrealized investment loss related to noncontrolling interest	0	1
End of period	(148,252)	(589,521)
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income (loss) before income taxes	11,216	50,063
Tax effect	(2,355)	(10,513)
Net income (loss) before noncontrolling interests	8,861	39,550
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	289,714	124,514
Other comprehensive income (loss) before reclassifications	(98,991)	(298,531)
Amounts reclassified from AOCI	8,861	39,550
Other comprehensive loss	(90,130)	(258,981)
Unrealized investment loss related to noncontrolling interest	0	1
End of period	199,584	(109,514)
Total change in unrealized investment losses	(113,735)	(332,850)
Unrealized investment gains, tax effect	23,605	73,869
Unrealized investment gains (losses), after-tax amounts	(90,130)	(258,981)
Unrealized Investment Gains (Losses) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net realized and unrealized gains (losses) on investments	11,216	50,063
Tax effect	(2,355)	(10,513)
Net income (loss) before noncontrolling interests	8,861	39,550
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(351,886)	(381,813)
Other comprehensive income (loss) before reclassifications	4,050	(98,194)
Amounts reclassified from AOCI	0	0
Other comprehensive loss	4,050	(98,194)
Unrealized investment loss related to noncontrolling interest	0	0
End of period	(347,836)	(480,007)
Currency translation adjustment, pre-tax	4,050	(98,194)
Currency translation adjustment, tax effect	0	0
Net change in period	4,050	(98,194)
Currency Translation Adjustments | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income (loss) before income taxes	0	0
Tax effect	0	0
Net income (loss) before noncontrolling interests	0	$ 0
Cumulative effect adjustment resulting from changes in accounting principles | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	24,952
Cumulative effect adjustment resulting from changes in accounting principles | Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	24,952
Cumulative effect adjustment resulting from changes in accounting principles | Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	0
Cumulative Effect, Period Of Adoption, Adjusted Balance | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(232,347)
Cumulative Effect, Period Of Adoption, Adjusted Balance | Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	149,466
Cumulative Effect, Period Of Adoption, Adjusted Balance | Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	$ (381,813)