Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Common Shares
Weighted average Common Shares outstanding (in shares)									129,735,723	125,219,773	119,739,216
Non-vested shares (in shares)									(1,736,022)	(1,927,648)	(1,813,058)
Weighted average Common Shares - Basic (in shares)									127,999,701	123,292,125	117,926,158
Dilutive effect of employee stock purchase plan (in shares)									84,283	58,808	91,007
Weighted average Common Shares - Diluted (in shares)									128,083,984	123,350,933	118,017,165
Net income									$ 39,185	$ 69,771	$ 23,092
Dividends paid on nonvested share-based awards									(2,075)	(2,320)
Dividends paid on nonvested share-based awards											(2,149)
Net income applicable to common stockholders									$ 37,110	$ 67,451	$ 20,943
Basic earnings per common share (in USD per share)	$ 0.20	$ 0.02	$ 0.03	$ 0.04	$ 0.13	$ 0.05	$ 0.30	$ 0.07	$ 0.29	$ 0.55	$ 0.18
Diluted earnings per common share (in USD per share)	$ 0.20	$ 0.02	$ 0.03	$ 0.04	$ 0.13	$ 0.05	$ 0.30	$ 0.07	$ 0.29	$ 0.55	$ 0.18