CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (27,689)	$ (25,826)	$ (83,988)	$ (79,250)
Other comprehensive gain, before tax:
Net change in unrealized gain (loss) on available-for-sale investments	80	(35)	213	80
Foreign currency translation gain (loss)	0	(227)	824	570
Net change in unrealized gain (loss) on derivative instruments	344	416	3,692	139
Other comprehensive gain, before tax	424	154	4,729	789
Tax effect	(156)	(61)	(1,737)	(295)
Other comprehensive gain, net of tax	268	93	2,992	494
Comprehensive loss	$ (27,421)	$ (25,733)	$ (80,996)	$ (78,756)