Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income before noncontrolling interests	$ 164,443	$ 162,818	$ 512,794	$ 397,065
Other comprehensive (loss) income:
Change in unrealized currency translation adjustments	15,686	28,592	(75,970)	71,574
Change in unrealized investment (losses) gains, net of taxes	(94,842)	(8,168)	(253,056)	26,598
Other comprehensive income (loss)	(79,156)	20,424	(329,026)	98,172
Comprehensive income	85,287	183,242	183,768	495,237
Noncontrolling interests	(2,463)	(731)	(4,316)	(2,541)
Comprehensive income to common stockholders	$ 82,824	$ 182,511	$ 179,452	$ 492,696