Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Non-controlling Interests	Total
Balance at Dec. 31, 2015	$ 4	$ 197,612	$ (85,176)	$ (1,160)	$ 755	$ 112,035
Balance (in shares) at Dec. 31, 2015	37,325
Issuance of common stock under stock incentive plans		2,984				2,984
Issuance of common stock under stock incentive plans (in shares)	1,237
Shares withheld for taxes		(2,827)				(2,827)
Stock-based compensation expense		13,412				13,412
Non-controlling interest distributions					(286)	(286)
Cumulative effect of a change in accounting principle		94	(94)
Net income (loss)			(27,331)		348	(26,983)
Other comprehensive (loss) income				290	(79)	211
Balance at Dec. 31, 2016	$ 4	211,275	(112,601)	(870)	738	98,546
Balance (in shares) at Dec. 31, 2016	38,562
Issuance of common stock under stock incentive plans		9,244				9,244
Issuance of common stock under stock incentive plans (in shares)	2,433
Shares withheld for taxes		(4,872)				(4,872)
Stock-based compensation expense		15,032				15,032
Non-controlling interest distributions					(125)	(125)
Net income (loss)			(19,366)		590	(18,776)
Other comprehensive (loss) income				(28)	9	(19)
Balance at Dec. 31, 2017	$ 4	230,679	(131,967)	(898)	1,212	$ 99,030
Balance (in shares) at Dec. 31, 2017	40,995					40,995
Issuance of common stock under stock incentive plans		9,979				$ 9,979
Issuance of common stock under stock incentive plans (in shares)	1,674
Shares withheld for taxes		(10,536)				(10,536)
Stock-based compensation expense		13,057				13,057
Equity component of Convertible Notes, net of offering costs and tax		39,922				39,922
Payment for capped call share options		(23,969)				(23,969)
Non-controlling interest distributions					(614)	(614)
Cumulative effect of a change in accounting principle			3,257		69	3,326
Net income (loss)			(1,220)		1,489	269
Other comprehensive (loss) income				(397)	55	(342)
Balance at Dec. 31, 2018	$ 4	$ 259,132	$ (129,930)	$ (1,295)	$ 2,211	$ 130,122
Balance (in shares) at Dec. 31, 2018	42,669					42,669