Unaudited Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Unaudited Condensed Consolidated Statement of Comprehensive Income [Abstract]
Net income	$ 70,872	$ 68,993	$ 222,598	$ 254,322
Other comprehensive income:
Foreign currency translation adjustments	(4,266)	5,951	10,133	(9,550)
Total comprehensive income	66,606	74,944	232,731	244,772
Total comprehensive income attributable to noncontrolling interests	(79)	(59)	(155)	(157)
Total comprehensive income attributable to common stockholders	$ 66,527	$ 74,885	$ 232,576	$ 244,615