Summary of Significant Accounting Policies - Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounting Policies [Abstract]
Net Income (Loss)	$ 11,114	$ (29,360)	$ (87,025)	$ (101,203)
Basic weighted-average common shares outstanding in period (in shares)	210,549,653	209,501,887	210,288,446	181,144,822
Add dilutive effects of stock options and nonvested equity shares of common stock (in shares)	387,000	0	0	0
Diluted weighted-average common shares outstanding in period (in shares)	210,937,271	209,501,887	210,288,446	181,144,822
Basic net income (loss) per common share (in dollars per share)	$ 0.05	$ (0.14)	$ (0.41)	$ (0.56)
Diluted net income (loss) per common share (in dollars per share)	$ 0.05	$ (0.14)	$ (0.41)	$ (0.56)