Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			$ 6,118,342
Other comprehensive income (loss)	$ 340,172	$ 104,157	(17,004)	$ 249,692
End of period	5,845,391		5,845,391
Net realized and unrealized gains (losses) on investments	61,653	73,574	(81,632)	142,226
Income before income taxes	105,449	273,736	98,982	503,175
Tax effect	(33,793)	(56,309)	(30,852)	(104,134)
Net income before noncontrolling interests	71,656	217,427	68,130	399,041
Total change in unrealized investment gains	395,624	147,071	62,777	316,331
Net change in period	21,447	(14,492)	(76,747)	5,268
Other comprehensive income (loss), pre-tax	417,071	132,580	(13,970)	321,599
Other comprehensive income (loss), tax effect	(76,899)	(28,423)	(3,034)	(71,907)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(589,521)	(364,983)	(257,299)	(510,470)
Other comprehensive income (loss) before reclassifications	356,965	103,983	(39,761)	250,883
Amounts reclassified from AOCI	(16,793)	174	22,757	(1,191)
Other comprehensive income (loss)	340,172	104,157	(17,004)	249,692
Unrealized investment gain related to noncontrolling interest	(1)	30	1	(18)
End of period	(249,350)	(260,796)	(249,350)	(260,796)
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	(21,257)	220	28,806	(1,508)
Tax effect	4,464	(46)	(6,049)	317
Net income before noncontrolling interests	(16,793)	174	22,757	(1,191)
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(109,514)	34,236	124,514	(91,491)
Other comprehensive income (loss) before reclassifications	335,518	118,475	36,986	245,615
Amounts reclassified from AOCI	(16,793)	174	22,757	(1,191)
Other comprehensive income (loss)	318,725	118,649	59,743	244,424
Unrealized investment gain related to noncontrolling interest	(1)	30	1	(18)
End of period	209,210	152,915	209,210	152,915
Total change in unrealized investment gains	395,624	147,072	62,777	316,331
Unrealized investment gains, tax effect	(76,899)	(28,423)	(3,034)	(71,907)
Unrealized investment gains (losses), after-tax amounts	318,725	118,649	59,743	244,424
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	(21,257)	220	28,806	(1,508)
Tax effect	4,464	(46)	(6,049)	317
Net income before noncontrolling interests	(16,793)	174	22,757	(1,191)
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(480,007)	(399,219)	(381,813)	(418,979)
Other comprehensive income (loss) before reclassifications	21,447	(14,492)	(76,747)	5,268
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive income (loss)	21,447	(14,492)	(76,747)	5,268
Unrealized investment gain related to noncontrolling interest	0	0	0	0
End of period	(458,560)	(413,711)	(458,560)	(413,711)
Currency translation adjustment, pre-tax	21,447	(14,492)	(76,747)	5,268
Currency translation adjustment, tax effect	0	0	0	0
Net change in period	21,447	(14,492)	(76,747)	5,268
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)