Unaudited Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Unaudited Condensed Consolidated Statement of Comprehensive Income [Abstract]
Net income	$ 82,048	$ 174,749
Other comprehensive income:
Foreign currency translation adjustments	(9,592)	3,164
Total comprehensive income	72,456	177,913
Total comprehensive income attributable to noncontrolling interests	(57)	(47)
Total comprehensive income attributable to common stockholders	$ 72,399	$ 177,866