Summary of Significant Accounting Policies - Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net Income (Loss)	$ 121,220	$ (138,225)	$ (170,378)
Basic weighted-average common shares outstanding in period (in shares)	188,299,074	76,858,815	55,384,020
Add dilutive effects of stock options and nonvested equity shares of common stock (in shares)	941,962	0	0
Diluted weighted-average common shares outstanding in period (in shares)	189,241,036	76,858,815	55,384,020
Basic net income (loss) per common share (in dollars per share)	$ 0.64	$ (1.80)	$ (3.08)
Diluted net income (loss) per common share (in dollars per share)	$ 0.64	$ (1.80)	$ (3.08)