Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			$ 6,118,342
Other comprehensive income (loss)	$ 78,467	$ (61,427)	61,463	$ 188,265
End of period	6,039,672		6,039,672
Net realized and unrealized (losses) gains on investments	(7,772)	1,465	(89,404)	143,691
Income before income taxes	206,414	202,982	305,395	706,157
Tax effect	(54,048)	(37,831)	(84,900)	(141,965)
Net income before noncontrolling interests	152,366	165,151	220,495	564,192
Total change in unrealized investment gains (losses)	48,980	(28,592)	111,756	287,739
Net change in period	40,194	(36,682)	(36,553)	(31,414)
Other comprehensive income (loss), pre-tax	89,174	(65,274)	75,203	256,325
Other comprehensive income (loss), tax effect	(10,707)	3,847	(13,740)	(68,060)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(249,350)	(260,796)	(257,299)	(510,470)
Other comprehensive income (loss) before reclassifications	79,682	(63,705)	39,921	187,178
Amounts reclassified from AOCI	(1,215)	2,278	21,542	1,087
Other comprehensive income (loss)	78,467	(61,427)	61,463	188,265
Unrealized investment loss related to noncontrolling interest	(3)	123	(2)	105
End of period	(170,886)	(322,100)	(170,886)	(322,100)
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	(1,538)	2,884	27,268	1,376
Tax effect	323	(606)	(5,726)	(289)
Net income before noncontrolling interests	(1,215)	2,278	21,542	1,087
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	209,210	152,915	124,514	(91,491)
Other comprehensive income (loss) before reclassifications	39,488	(27,023)	76,474	218,592
Amounts reclassified from AOCI	(1,215)	2,278	21,542	1,087
Other comprehensive income (loss)	38,273	(24,745)	98,016	219,679
Unrealized investment loss related to noncontrolling interest	(3)	123	(2)	105
End of period	247,480	128,293	247,480	128,293
Total change in unrealized investment gains (losses)	48,980	(28,592)	111,756	287,739
Unrealized investment gains, tax effect	(10,707)	3,847	(13,740)	(68,060)
Unrealized investment gains (losses), after-tax amounts	38,273	(24,745)	98,016	219,679
Unrealized Investment Gains (Losses) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net realized and unrealized (losses) gains on investments	(1,538)	2,884	27,268	1,376
Tax effect	323	(606)	(5,726)	(289)
Net income before noncontrolling interests	(1,215)	2,278	21,542	1,087
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(458,560)	(413,711)	(381,813)	(418,979)
Other comprehensive income (loss) before reclassifications	40,194	(36,682)	(36,553)	(31,414)
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive income (loss)	40,194	(36,682)	(36,553)	(31,414)
Unrealized investment loss related to noncontrolling interest	0	0	0	0
End of period	(418,366)	(450,393)	(418,366)	(450,393)
Currency translation adjustment, pre-tax	40,194	(36,682)	(36,553)	(31,414)
Currency translation adjustment, tax effect	0	0	0	0
Net change in period	40,194	(36,682)	(36,553)	(31,414)
Currency Translation Adjustments | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	0	0	0	0
Tax effect	0	0	0	0
Net income before noncontrolling interests	$ 0	$ 0	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)