Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			$ 68,541
Other comprehensive income (loss)	$ (136,897)	$ 63,844	(249,870)	$ 77,748
End of period	(395,842)		(395,842)
Net realized and unrealized gains on investments	69,631	40,453	118,095	92,801
Income before income taxes	229,242	160,961	440,232	345,258
Other Cost and Expense, Operating	593,142	616,632	1,203,581	1,220,332
Tax effect	(48,464)	(51,388)	(91,881)	(111,011)
Net income before noncontrolling interests	180,778	109,573	348,351	234,247
Net change in period	(104,455)	20,247	(91,656)	42,982
Other comprehensive income (loss), pre-tax	(144,943)	88,529	(292,992)	101,693
Other comprehensive income (loss), tax effect	8,046	(24,685)	43,122	(23,945)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(258,982)	69,491	(145,998)
Other comprehensive income (loss) before reclassifications	(133,898)	89,562	(239,288)	132,291
Amounts reclassified from AOCI	(2,999)	(25,718)	(10,582)	(54,543)
Other comprehensive income (loss)	(136,897)	63,844	(249,870)	77,748
Unrealized investment loss related to noncontrolling interest	37	(33)	26	(14)
End of period	(395,842)	133,302	(395,842)	133,302
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	(3,796)	(39,566)	(13,395)	(83,912)
Tax effect	797	13,848	2,813	29,369
Net income before noncontrolling interests	(2,999)	(25,718)	(10,582)	(54,543)
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	35,099	418,342	160,882
Other comprehensive income (loss) before reclassifications	(29,443)	69,315	(147,632)	89,309
Amounts reclassified from AOCI	(2,999)	(25,718)	(10,582)	(54,543)
Other comprehensive income (loss)	(32,442)	43,597	(158,214)	34,766
Unrealized investment loss related to noncontrolling interest	37	(33)	26	(14)
End of period	2,694	461,906	2,694	461,906
Unrealized investment gains, pre-tax	(40,488)	68,282	(201,336)	58,711
Unrealized investment gains, tax effect	8,046	(24,685)	43,122	(23,945)
Unrealized investment gains (losses), after-tax amounts	(32,442)	43,597	(158,214)	34,766
Unrealized Investment Gains (Losses) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net realized and unrealized gains on investments	(3,796)	(39,566)	(13,395)	(83,912)
Tax effect	797	13,848	2,813	29,369
Net income before noncontrolling interests	(2,999)	(25,718)	(10,582)	(54,543)
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(294,081)	(348,851)	(306,880)
Other comprehensive income (loss) before reclassifications	(104,455)	20,247	(91,656)	42,982
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive income (loss)	(104,455)	20,247	(91,656)	42,982
Unrealized investment loss related to noncontrolling interest	0	0	0	0
End of period	(398,536)	(328,604)	(398,536)	(328,604)
Currency translation adjustment, pre-tax	(104,455)	20,247	(91,656)	42,982
Currency translation adjustment, tax effect	0	0	0	0
Net change in period	(104,455)	20,247	(91,656)	42,982
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
Scenario, Previously Reported | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			68,541	55,568
Scenario, Previously Reported | Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			375,421	427,154
Scenario, Previously Reported | Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			(306,880)	$ (371,586)
Restatement Adjustment | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			(214,539)
Restatement Adjustment | Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			(214,539)
Restatement Adjustment | Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			$ 0