Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 40,769	$ 27,484	$ 97,100	$ 74,148
Earnings allocated to participating securities - preferred shares	0	48	4	131
Earnings allocated to participating securities - nonvested restricted shares	558	378	1,325	953
Earnings allocated to common shareholders, Basic	$ 40,211	$ 27,058	$ 95,771	$ 73,064
Weighted average common shares outstanding	57,566	57,215	57,459	57,173
Basic earnings per common share	$ 0.70	$ 0.47	$ 1.67	$ 1.28
Earnings allocated to common shareholders, Diluted	$ 40,211	$ 27,058	$ 95,771	$ 73,064
Dilutive effect of equity awards and warrants	5	10	6	10
Weighted average diluted common shares outstanding	57,571	57,225	57,465	57,183
Diluted earnings per common share	$ 0.70	$ 0.47	$ 1.67	$ 1.28
Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive.	12	15	13	20