Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 27,132	$ 25,405	$ 56,331	$ 46,664
Earnings allocated to participating securities - preferred shares	0	45	3	82
Earnings allocated to participating securities - nonvested restricted shares	362	343	759	578
Earnings allocated to common shareholders, Basic	$ 26,770	$ 25,017	$ 55,569	$ 46,004
Weighted average common shares outstanding	57,520	57,185	57,437	57,149
Basic earnings per common share	$ 0.47	$ 0.44	$ 0.97	$ 0.80
Earnings allocated to common shareholders, Diluted	$ 26,770	$ 25,017	$ 55,569	$ 46,004
Dilutive effect of equity awards and warrants	5	10	5	11
Weighted average diluted common shares outstanding	57,525	57,195	57,442	57,160
Diluted earnings per common share	$ 0.47	$ 0.44	$ 0.97	$ 0.80
Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive.	12	19	13	23