Earnings Per Share - Summary (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic:
Net (Loss) Income	$ 9,639	$ 6,278	$ (237,963)	$ (311,253)	$ (175,293)	$ (713,445)	$ (54,885)	$ (110,956)	$ (879,286)	$ (533,299)	$ (1,054,579)	$ 312,908
Less: Net (loss) income allocable to participating RSUs										0	0	(1,377)
Net (loss) income available for basic common shares										$ (533,299)	$ (1,054,579)	$ 311,531
Weighted average common shares outstanding (in shares)	345,720	345,285	344,584	344,434	344,294	343,870	343,116	342,914	343,304	345,012	343,564	341,480
Basic net (loss) income per common share (USD per share)	$ 0.03	$ 0.02	$ (0.69)	$ (0.90)	$ (0.51)	$ (2.07)	$ (0.16)	$ (0.32)	$ (2.56)	$ (1.55)	$ (3.07)	$ 0.91
Diluted:
Net (Loss) Income	$ 9,639	$ 6,278	$ (237,963)	$ (311,253)	$ (175,293)	$ (713,445)	$ (54,885)	$ (110,956)	$ (879,286)	$ (533,299)	$ (1,054,579)	$ 312,908
Less: Net (loss) income allocable to participating RSUs										0	0	(1,377)
Net (loss) income available for diluted common shares										$ (533,299)	$ (1,054,579)	$ 311,531
Weighted average common shares outstanding (in shares)	345,720	345,285	344,584	344,434	344,294	343,870	343,116	342,914	343,304	345,012	343,564	341,480
Weighted average common equivalent shares arising from:
Dilutive stock options and non-participating RSUs (in shares)										0	0	2,753
Weighted average number of common and potential common shares (in shares)	345,846	345,672	344,584	344,434	344,294	343,870	343,116	342,914	343,304	345,012	343,564	344,233
Diluted net (loss) income per common share (USD per share)	$ 0.03	$ 0.02	$ (0.69)	$ (0.90)	$ (0.51)	$ (2.07)	$ (0.16)	$ (0.32)	$ (2.56)	$ (1.55)	$ (3.07)	$ 0.91