Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 26,456	$ 26,623
Other comprehensive income (loss):
Foreign currency translation adjustments	(4,759)	2,517
Total other comprehensive income (loss)	(4,759)	2,517
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	21,697	29,140
Net Income (Loss) Attributable to Noncontrolling Interest	248	196
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 21,449	$ 28,944