Net Income Per Common Share - Calculation of Diluted Net Income Per Common Share (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income (loss)	$ (403,922)	$ 25,826	$ (399,106)	$ 22,708
Denominator:
Weighted-average common shares, basic	164,926	158,505	164,586	157,576
Dilutive effect of common stock equivalents	0	10,185	0	5,419
Weighted-average common shares, diluted	164,926	168,690	164,586	162,995