Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income before noncontrolling interests	$ 167,573	$ 124,674
Other comprehensive (loss) income:
Change in unrealized currency translation adjustments	12,799	22,735
Change in unrealized investment gains, net of taxes	(125,772)	(8,831)
Other comprehensive income (loss)	(112,973)	13,904
Comprehensive income	54,600	138,578
Noncontrolling interests	(1,188)	(1,208)
Comprehensive income to common stockholders	$ 53,412	$ 137,370