Loss Per Common Share - Computations of Basic and Diluted Loss Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share Reconciliation [Abstract]
Net loss, as reported		$ (41,971)	$ (300,948)	$ (358,617)	$ (391,858)
Participating earnings	[1]	(56)	(114)	(167)	(338)
Basic net loss attributed to common shareholders		(42,027)	(301,062)	(358,784)	(392,196)
Reallocation of participating earnings	[1]	0	0	0	0
Diluted net loss attributed to common shareholders		$ (42,027)	$ (301,062)	$ (358,784)	$ (392,196)
Net loss per common share:
Basic		$ (0.23)	$ (1.81)	$ (2.09)	$ (2.36)
Diluted		$ (0.23)	$ (1.81)	$ (2.09)	$ (2.36)

[1] Restricted Stock Awards represent participating securities because they participate in nonforfeitable dividends or distributions with common equity owners. Income allocable to participating securities represents the distributed and undistributed earnings attributable to the participating securities. Participating securities, however, do not participate in undistributed net losses.