Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period			$ 55,568
Other comprehensive income (loss)	$ 20,424	$ (67,146)	98,172	$ 56,824
End of period	153,759		153,759
Net realized investment gains	183,959	175,738	276,760	207,508
Income before income taxes	226,113	331,615	571,370	664,605
Tax effect	(63,295)	(110,952)	(174,305)	(214,789)
Net income before noncontrolling interests	162,818	220,663	397,065	449,816
Net change in period	28,592	(19,470)	71,574	(77,389)
Other comprehensive income (loss), pre-tax	20,029		121,722
Other comprehensive income (loss), tax effect	395		(23,550)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	133,302	57,281	55,568	(66,698)
Other comprehensive income (loss) before reclassifications	48,560	(40,438)	180,851	93,435
Amounts reclassified from AOCI	(28,136)	(26,708)	(82,679)	(36,611)
Other comprehensive income (loss)	20,424	(67,146)	98,172	56,824
Unrealized investment loss related to non-controlling interest	33	57	19	66
End of period	153,759	(9,808)	153,759	(9,808)
Other comprehensive income (loss), pre-tax		(91,658)		121,419
Other comprehensive income (loss), tax effect		24,512		(64,595)
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	(43,286)	(41,090)	(127,198)	(56,325)
Tax effect	15,150	14,382	44,519	19,714
Net income before noncontrolling interests	(28,136)	(26,708)	(82,679)	(36,611)
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	461,906	362,593	427,154	180,695
Other comprehensive income (loss) before reclassifications	19,968	(20,968)	109,277	170,824
Amounts reclassified from AOCI	(28,136)	(26,708)	(82,679)	(36,611)
Other comprehensive income (loss)	(8,168)	(47,676)	26,598	134,213
Unrealized investment loss related to non-controlling interest	33	57	19	66
End of period	453,771	314,974	453,771	314,974
Unrealized investment gains, pre-tax	(8,563)	(72,188)	50,148	198,808
Unrealized investment gains, tax effect	395	24,512	(23,550)	(64,595)
Unrealized investment gains (losses), after-tax amounts	(8,168)	(47,676)	26,598	134,213
Unrealized Investment Gains (Losses) | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net realized investment gains	(43,286)	(41,090)	(127,198)	(56,325)
Tax effect	15,150	14,382	44,519	19,714
Net income before noncontrolling interests	(28,136)	(26,708)	(82,679)	(36,611)
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning of period	(328,604)	(305,312)	(371,586)	(247,393)
Other comprehensive income (loss) before reclassifications	28,592	(19,470)	71,574	(77,389)
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive income (loss)	28,592	(19,470)	71,574	(77,389)
Unrealized investment loss related to non-controlling interest	0	0	0	0
End of period	(300,012)	(324,782)	(300,012)	(324,782)
Currency translation adjustment, pre-tax	28,592	(19,470)	71,574	(77,389)
Currency translation adjustment, tax effect	0	0	0	0
Net change in period	28,592	(19,470)	71,574	(77,389)
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