Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Common Shares
Weighted average Common Shares outstanding (in shares)									125,219,773	119,739,216	109,861,580
Non-vested shares (in shares)									(1,927,648)	(1,813,058)	(1,289,478)
Weighted average Common Shares - Basic (in shares)									123,292,125	117,926,158	108,572,102
Dilutive effect of non-vested shares (in shares)											709,559
Dilutive effect of employee stock purchase plan (in shares)									58,808	91,007	105,336
Weighted average Common Shares - Diluted (in shares)									123,350,933	118,017,165	109,386,997
Net Income									$ 69,771	$ 23,092	$ 85,571
Dividends paid on nonvested share-based awards									(2,320)	(2,149)
Net income applicable to common stockholders					$ 23,092				$ 67,451	$ 20,943	$ 85,571
Basic earnings per common share (dollars per share)	$ 0.13	$ 0.05	$ 0.30	$ 0.07	$ (0.31)	$ 0.02	$ 0.22	$ 0.28	$ 0.55	$ 0.18	$ 0.79
Diluted earnings per common share (dollars per share)	$ 0.13	$ 0.05	$ 0.30	$ 0.07	$ (0.31)	$ 0.02	$ 0.22	$ 0.28	$ 0.55	$ 0.18	$ 0.78