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								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income (loss)	$ 164,205	$ 77,993	$ 47,919	$ (13,665)	$ 2,768	$ (13,313)	$ (4,898)	$ (27,170)	$ 276,452	$ (42,613)	$ (41,257)
Interest expense on convertible notes, net of tax									14,030
Numerator for diluted net income (loss) per common share calculation									$ 290,482	$ (42,613)	$ (41,257)
Denominator:
Weighted-average common shares, basic	77,822	77,056	76,577	76,245	75,560	75,255	75,013	74,824	76,929	75,165	73,480
Dilutive effect of common stock equivalents									8,071
Weighted-average common shares, diluted	85,756	81,223	80,491	76,245	79,912	75,255	75,013	74,824	85,000	75,165	73,480
Basic net income (loss) per common share	$ 2.11	$ 1.01	$ 0.63	$ (0.18)	$ 0.04	$ (0.18)	$ (0.07)	$ (0.36)	$ 3.59	$ (0.57)	$ (0.56)
Diluted net income (loss) per common share	$ 1.96	$ 0.96	$ 0.60	$ (0.18)	$ 0.03	$ (0.18)	$ (0.07)	$ (0.36)	$ 3.42	$ (0.57)	$ (0.56)