Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	5,190,897	37,549,948	5,190,897	37,549,948
Numerator:
Net loss	$ (19,334)	$ (23,375)	$ (46,470)	$ (51,401)
Accretion of convertible redeemable preferred units		(4,605)		(11,755)
Net loss attributable to common stockholders	$ (19,334)	$ (27,980)	$ (46,470)	$ (63,156)
Denominator:
Weighted average common shares used for basic and diluted net loss per share computation	83,603,000	40,515,000	83,407,000	40,829,000
Net loss per common unit attributable to common stockholders:
Basic and Diluted (in dollars per unit)	$ (0.23)	$ (0.69)	$ (0.56)	$ (1.55)
Series A convertible redeemable preferred units
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share		21,551,801		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		5,995,133		5,995,133
Stock options
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	337,148	646,413	337,148	646,413
Restricted stock
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	12,563	3,271,516	12,563	3,271,516
Restricted stock units
Anti-dilutive securities
Common stockholders outstanding that were excluded from the computation of diluted net loss per share	4,841,186	6,085,085	4,841,186	6,085,085
Class B common stock
Numerator:
Net loss	$ (19,334)	$ (23,375)	$ (46,470)	$ (51,401)
Accretion of convertible redeemable preferred units		(4,605)		(11,755)
Net loss attributable to common stockholders	$ (19,334)	$ (27,980)	$ (46,470)	$ (63,156)
Denominator:
Weighted average common shares used for basic and diluted net loss per share computation	83,603,000	40,515,000	83,407,000	40,829,000
Net loss per common unit attributable to common stockholders:
Basic and Diluted (in dollars per unit)	$ (0.23)	$ (0.69)	$ (0.56)	$ (1.55)