Basis of Presentation and Significant Accounting Policies - Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Weighted Average Number Diluted Shares Outstanding Adjustment				2,558,900
Net income (loss) (numerator)
Net income (loss) (numerator)	$ 314,169	$ 10,621	$ 790,580	$ (52,467)
Weighted average shares - basic	371,960,000	371,142,000	371,810,000	371,029,000
Non-vested restricted stock (1)	2,663,000	1,873,000	2,952,000	0	[1]
Weighted average shares - diluted	374,623,000	373,015,000	374,762,000	371,029,000
Net income (loss) per share:
Basic (in dollars per share)	$ 0.84	$ 0.03	$ 2.13	$ (0.14)
Diluted (in dollars per share)	$ 0.84	$ 0.03	$ 2.11	$ (0.14)

[1] For the nine months ended September 30, 2017, the Company had a net loss and therefore the potential dilutive effect of approximately 2,558,900 weighted average non-vested restricted shares were not included in the calculation of diluted net loss per share because to do so would have been anti-dilutive to the computation.