Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 41,749	$ 27,132	$ 81,719	$ 56,331
Earnings allocated to participating securities - preferred shares	0	0	0	3
Earnings allocated to participating securities - nonvested restricted shares	473	362	909	759
Earnings allocated to common shareholders, Basic	$ 41,276	$ 26,770	$ 80,810	$ 55,569
Weighted average common shares outstanding	72,385	57,520	72,343	57,437
Basic earnings per common share	$ 0.57	$ 0.47	$ 1.12	$ 0.97
Earnings allocated to common shareholders, Diluted	$ 41,276	$ 26,770	$ 80,810	$ 55,569
Dilutive effect of equity awards and warrants	5	5	4	5
Weighted average diluted common shares outstanding	72,390	57,525	72,347	57,442
Diluted earnings per common share	$ 0.57	$ 0.47	$ 1.12	$ 0.97
Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive.	3	12	7	13