Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Common Shares
Weighted average Common Shares outstanding									119,739,216	109,861,580	100,280,059
Non-vested shares									(1,813,058)	(1,289,478)	(1,108,707)
Weighted average Common Shares - Basic									117,926,158	108,572,102	99,171,352
Dilutive effect of non-vested shares									0	709,559	623,212
Dilutive effect of employee stock purchase plan									91,007	105,336	85,738
Weighted average Common Shares - Diluted									118,017,165	109,386,997	99,880,302
Net Income
Income (loss) from continuing operations	$ (37,151)	$ 3,165	$ 25,224	$ 31,858	$ 52,580	$ 11,857	$ 12,157	$ 9,163	$ 23,096	$ 85,756	$ 58,836
Dividends paid on nonvested share-based awards									(2,149)	0	0
Income from continuing operations applicable to common stockholders									20,947	85,756	58,836
Discontinued operations	0	8	0	(13)	(143)	(23)	(12)	(7)	(4)	(185)	10,600
NET INCOME	$ (37,151)	$ 3,173	$ 25,224	$ 31,845	$ 52,437	$ 11,834	$ 12,145	$ 9,156	$ 20,943	$ 85,571	$ 69,436
Basic Earnings (loss) Per Common Share
Income from continuing operations (in dollars per share)									$ 0.18	$ 0.79	$ 0.59
Income from discontinued operations (in dollars per share)									0.00	0.00	0.11
Net income (in dollars per share)	$ (0.31)	$ 0.02	$ 0.22	$ 0.28	$ 0.46	$ 0.10	$ 0.12	$ 0.09	0.18	0.79	0.70
Diluted Earnings (loss) Per Common Share
Income from continuing operations (in dollars per share)									0.18	0.78	0.59
Income from discontinued operations (in dollars per share)									0.00	0.00	0.11
Net income (in dollars per share)	$ (0.31)	$ 0.02	$ 0.22	$ 0.28	$ 0.45	$ 0.10	$ 0.12	$ 0.09	$ 0.18	$ 0.78	$ 0.70