Net Income (Loss) Per Common Share - Computations of Basic and Diluted Income (Loss) Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share Reconciliation [Abstract]
Net income (loss)		$ 221,185	$ (127,700)	$ 69,550	$ 170,111	$ (160,709)	$ (41,971)	$ (224,936)	$ (93,772)	$ 333,146	$ (521,388)	$ (713,685)
Participating basic earnings	[1]									(3,751)	(223)	(450)
Basic net income (loss) attributed to common stockholders										329,395	(521,611)	(714,135)
Reallocation of participating earnings	[1]									5	0	0
Diluted net income (loss) attributed to common stockholders										$ 329,400	$ (521,611)	$ (714,135)
Net income (loss) per common share:
Basic		$ 0.89	$ (0.52)	$ 0.28	$ 0.69	$ (0.66)	$ (0.23)	$ (1.35)	$ (0.56)	$ 1.34	$ (2.75)	$ (4.29)
Diluted		$ 0.89	$ (0.52)	$ 0.28	$ 0.69	$ (0.66)	$ (0.23)	$ (1.35)	$ (0.56)	$ 1.34	$ (2.75)	$ (4.29)

[1] Restricted stock Liability 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.