Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	5,223,956	38,390,937	5,223,956	38,390,937
Numerator:
Net loss	$ (15,478)	$ (24,143)	$ (61,948)	$ (75,544)
Accretion of convertible redeemable preferred units	0	(4,748)	0	(16,503)
Net loss attributable to common stockholders	$ (15,478)	$ (28,891)	$ (61,948)	$ (92,047)
Denominator:
Weighted average common shares used for basic and diluted net loss per share computation (in shares)	83,886,000	40,513,000	83,569,000	40,722,000
Net loss unit attributable to common stockholders per share:
Basic and Diluted (in dollars per share)	$ (0.18)	$ (0.71)	$ (0.74)	$ (2.26)
Series A convertible redeemable preferred units
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	0	21,551,801	0	21,551,801
Series B convertible redeemable preferred units
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	0	5,995,133	0	5,995,133
Stock options
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	302,617	643,003	302,617	643,003
Restricted stock
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	6,001	3,271,516	6,001	3,271,516
Restricted stock units
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	4,915,338	6,929,484	4,915,338	6,929,484
Class B common stock
Numerator:
Net loss	$ (15,478)	$ (24,143)	$ (61,948)	$ (75,544)
Accretion of convertible redeemable preferred units	0	(4,748)	0	(16,503)
Net loss attributable to common stockholders	$ (15,478)	$ (28,891)	$ (61,948)	$ (92,047)
Denominator:
Weighted average common shares used for basic and diluted net loss per share computation (in shares)	83,886,000		83,569,000
Net loss unit attributable to common stockholders per share:
Basic and Diluted (in dollars per share)	$ (0.18)	$ (0.71)	$ (0.74)	$ (2.26)