Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income before noncontrolling interests	$ 180,778	$ 109,573	$ 348,351	$ 234,247
Other comprehensive (loss) income:
Change in unrealized currency translation adjustments	(104,455)	20,247	(91,656)	42,982
Change in unrealized investment gains, net of taxes	(32,442)	43,597	(158,214)	34,766
Other comprehensive income (loss)	(136,897)	63,844	(249,870)	77,748
Comprehensive income	43,881	173,417	98,481	311,995
Noncontrolling interests	(666)	(602)	(1,853)	(1,810)
Comprehensive income to common stockholders	$ 43,215	$ 172,815	$ 96,628	$ 310,185