Stockholders' Equity - Schedule of Stockholders Equity (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares at beginning of period	110,363,539	75,721,360	49,864,512
Shares issued for directors' fees	187,566	68,486	97,299
Shares issued for nonvested shares of common stock	2,332,114	801,579	686,500
Shares issued for debt exchange	0
Shares retired or forfeited	(406,118)	(296,415)	(451,951)
Shares at end of period	212,477,101	110,363,539	75,721,360
Shares at beginning of period	0	0	0
Treasury stock acquired	285,807	243,389	227,561
Treasury stock retired	(285,807)	(243,389)	(227,561)
Shares at end of period	0	0	0
Common stock, shares issued	212,477,101	110,363,539
Seven Point Zero Percentage Senior Notes [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for debt exchange		10,863,000
Seven Point Six Two Five Percentage Senior Notes [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for debt exchange			10,000,000
Equity Offering [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares issued	0	23,205,529	15,525,000
Merger [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares issued	100,000,000	0	0