Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 546,847	$ 177,305	$ 234,934
Foreign currency translation adjustments	25,462	10,331	(53,283)
Total comprehensive income	572,309	187,636	181,651
Total comprehensive income attributable to noncontrolling interests	(195)	(270)	(1,129)
Total comprehensive income attributable to common stockholders	$ 572,114	$ 187,366	$ 180,522