Stockholders' Equity - Computation of basic and diluted earnings (loss) per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Weighted average Common Shares outstanding
Weighted average Common Shares outstanding	125,167,128	116,470,836
Nonvested shares	(1,909,777)	(1,795,752)
Weighted average Common Shares—Basic	123,257,351	114,675,084
Dilutive effect of nonvested share-based awards	0	725,346
Dilutive effect of employee stock purchase plan	90,330	106,572
Weighted average Common Shares outstanding—Diluted	123,347,681	115,507,002
Net Income
Net Income	$ 9,180	$ 31,845
Dividends paid on nonvested share-based awards	(579)	0
Net income applicable to common stockholders	$ 8,601	$ 31,845
Basic Earnings Per Common Share
Net income (in dollars per share)	$ 0.07	$ 0.28
Diluted Earnings Per Common Share
Net income (in dollars per share)	$ 0.07	$ 0.28