Common Stock and Loss Per Share - Reconciliation of Numerators and Denominators of Basic and Diluted Earnings (Loss) Per Share Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic and Diluted Loss Per Share [Abstract]
Net loss available to common stockholders (numerator)	$ (94,309)	$ (489,963)	$ (89,801)	$ (662,665)
Weighted-average common shares outstanding (denominator)	36,536	35,811	36,475	35,679
Basic and diluted loss per common and common equivalent share	$ (2.58)	$ (13.68)	$ (2.46)	$ (18.57)