Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 75,306	$ 93,512	$ 138,575
Other comprehensive income (loss), net of income tax:
Foreign currency translation adjustment	24,670	(9,847)	(40,776)
Total comprehensive income	99,976	83,665	97,799
Total comprehensive income attributable to:
Stockholders	99,639	81,839	95,831
Non-controlling interests	$ 337	$ 1,826	$ 1,968