Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 17,207	$ 10,433
Other comprehensive income, net of income tax:
Foreign currency translation adjustment	4,907	7,440
Total comprehensive income	22,114	17,873
Total comprehensive income attributable to:
Stockholders	22,033	17,813
Non-controlling interests	$ 81	$ 60