Net Income (Loss) per Share Attributable to Common Stockholders - Antidilutive Securities Excluded from Computation of Net Income per Share (Detail) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the calculation of diluted shares outstanding (shares)	15,921	32,312	55,357
Series A Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the calculation of diluted shares outstanding (shares)	15,136	30,523	30,523
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the calculation of diluted shares outstanding (shares)	360	1,409	24,402
Restricted Stock Awards and Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the calculation of diluted shares outstanding (shares)	425	380	432