Unaudited Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Unaudited Condensed Consolidated Statement of Comprehensive Income [Abstract]
Net income	$ 72,513	$ 103,281	$ 151,726	$ 185,329
Other comprehensive income:
Foreign currency translation adjustments	6,998	(5,909)	14,399	(15,501)
Total comprehensive income	79,511	97,372	166,125	169,828
Total comprehensive income attributable to noncontrolling interests	(36)	(41)	(76)	(98)
Total comprehensive income attributable to common stockholders	$ 79,475	$ 97,331	$ 166,049	$ 169,730