Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	$ 68,541
Other comprehensive income (loss)	(112,973)	$ 13,904
End of period	(258,982)
Net realized and unrealized gains on investments	48,464	52,348
Income before income taxes	210,990	184,297
Tax effect	(43,417)	(59,623)
Net income before noncontrolling interests	167,573	124,674
Net change in period	12,799	22,735
Other comprehensive income (loss), pre-tax	(148,049)	13,164
Other comprehensive income (loss), tax effect	35,076	740
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(145,998)	55,568
Other comprehensive income (loss) before reclassifications	(105,390)	42,729
Amounts reclassified from AOCI	(7,583)	(28,825)
Other comprehensive income (loss)	(112,973)	13,904
Unrealized investment gain related to noncontrolling interest	(11)	19
End of period	(258,982)	69,491
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	(9,599)	(44,346)
Tax effect	2,016	15,521
Net income before noncontrolling interests	(7,583)	(28,825)
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	160,882	427,154
Other comprehensive income (loss) before reclassifications	(118,189)	19,994
Amounts reclassified from AOCI	(7,583)	(28,825)
Other comprehensive income (loss)	(125,772)	(8,831)
Unrealized investment gain related to noncontrolling interest	(11)	19
End of period	35,099	418,342
Unrealized investment gains, pre-tax	(160,848)	(9,571)
Unrealized investment gains, tax effect	35,076	740
Unrealized investment gains (losses), after-tax amounts	(125,772)	(8,831)
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	(9,599)	(44,346)
Tax effect	2,016	15,521
Net income before noncontrolling interests	(7,583)	(28,825)
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(306,880)	(371,586)
Other comprehensive income (loss) before reclassifications	12,799	22,735
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss)	12,799	22,735
Unrealized investment gain related to noncontrolling interest	0	0
End of period	(294,081)	(348,851)
Currency translation adjustment, pre-tax	12,799	22,735
Currency translation adjustment, tax effect	0	0
Net change in period	12,799	22,735
Currency Translation Adjustments | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	0	0
Tax effect	0	0
Net income before noncontrolling interests	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
Scenario, Previously Reported | Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	375,421
Scenario, Previously Reported | Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(306,880)
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