Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income (loss)	$ (18,550)	$ (11,488)	$ (58,290)	$ 25,148
Noncumulative dividends on convertible preferred stock				(19,065)
Undistributed earnings allocated to participating securities				(5,761)
Net income (loss) attributable to common stockholders, basic	(18,550)	(11,488)	(58,290)	322
Adjustment to undistributed earnings allocated to participating securities				140
Net income (loss) attributable to common stockholders, diluted	$ (18,550)	$ (11,488)	$ (58,290)	$ 462
Basic shares:
Weighted average common shares outstanding	35,200,761	1,370,190	17,218,475	1,342,919
Shares used to compute net income (loss) per share attributable to common stockholders:
Weighted average common shares outstanding	35,200,761	1,370,190	17,218,475	1,342,919
Weighted average effect of dilutive stock options				633,699
Weighted average number of shares outstanding, Diluted shares	35,200,761	1,370,190	17,218,475	1,976,618
Net income (loss) per share attributable to common stockholders:
Basic	$ (0.53)	$ (8.38)	$ (3.39)	$ 0.24
Diluted	$ (0.53)	$ (8.38)	$ (3.39)	$ 0.23