Net Income (Loss) Per Common Share - Calculation of Diluted Net Income (Loss) Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:
Net income (loss)	$ 77,993	$ (13,313)	$ 112,247	$ (45,381)
Denominator:
Weighted-average common shares, basic	77,056	75,255	76,629	75,032
Dilutive effect of common stock equivalents	4,167		4,095
Weighted-average common shares, diluted	81,223	75,255	80,724	75,032
Basic net income (loss) per common share	$ 1.01	$ (0.18)	$ 1.46	$ (0.60)
Diluted net income (loss) per common share	$ 0.96	$ (0.18)	$ 1.39	$ (0.60)