Earnings Per Share Applicable to Common Stockholders - Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income (loss) applicable to common stockholders	$ 3,704	$ (11,744)	$ (26,840)	$ (31,187)
Weighted-average shares:
Basic	34,495,076	22,744,486	33,176,801	10,111,735
Effect of dilutive securities:
Diluted	36,592,683	22,744,486	33,176,801	10,111,735
Net income (loss) per share:
Basic	$ 0.11	$ (0.52)	$ (0.81)	$ (3.08)
Diluted	$ 0.10	$ (0.52)	$ (0.81)	$ (3.08)
Stock Options and Restricted Stock Units [Member]
Effect of dilutive securities:
Stock options and restricted stock units	2,085,068
Restricted Stock [Member]
Effect of dilutive securities:
Unvested restricted stock	12,523
Stock options [Member]
Effect of dilutive securities:
Employee stock purchase plan options	16