Net Income (Loss) Per Common Share - Calculation of Diluted Net Income (Loss) Per Common Share (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income (loss)	$ 142,507	$ 79,510	$ 25,826	$ (3,118)	$ 164,205	$ 77,993	$ 47,919	$ (13,665)	$ 244,725	$ 276,452	$ (42,613)
Interest expense on convertible notes, net of tax									3,629	14,030
Numerator for diluted net income (loss) per common share calculation									$ 248,354	$ 290,482	$ (42,613)
Denominator:
Weighted-average common shares used in the calculation of basic net income (loss) per common share	163,746	162,390	158,505	156,637	155,644	154,112	153,153	152,489	160,345	153,859	150,331
Dilutive effect of common stock equivalents									8,979	16,142
Weighted-average common shares, diluted	168,368	168,070	168,690	156,637	171,513	162,446	160,983	152,489	169,324	170,001	150,331