Net Income (Loss) Per Common Share - Calculation of Diluted Net (Loss) Income Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Net income (loss)	$ 47,919	$ (4,898)	$ 34,254	$ (32,068)
Denominator:
Weighted-average common shares, basic	76,577	75,013	76,411	74,919
Dilutive effect of common stock equivalents	3,914		4,076
Weighted-average common shares, diluted	80,491	75,013	80,487	74,919
Basic net income (loss) per common share	$ 0.63	$ (0.07)	$ 0.45	$ (0.43)
Diluted net income (loss) per common share	$ 0.60	$ (0.07)	$ 0.43	$ (0.43)