Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income		$ 25,780	$ 21,583	$ 72,087	$ 62,654
Earnings allocated to participating securities - preferred shares		45	42	127	121
Earnings allocated to participating securities - nonvested restricted shares		296	216	772	598
Earnings allocated to common shareholders, Basic		$ 25,439	$ 21,325	$ 71,188	$ 61,935
Weighted average common shares outstanding		57,051	52,112	57,007	51,772
Basic earnings per common share		$ 0.45	$ 0.41	$ 1.25	$ 1.20
Earnings allocated to common shareholders, Diluted	[1]	$ 25,439	$ 21,325	$ 71,188	$ 61,940
Dilutive effect of equity awards and warrants		13	404	14	707
Weighted average diluted common shares outstanding		57,064	52,516	57,021	52,479
Diluted earnings per common share		$ 0.45	$ 0.41	$ 1.25	$ 1.18
Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive.		29	58	40	67

[1] Earnings allocated to common shareholders for basic and diluted EPS may differ under the two-class method as a result of adding common stock equivalents for options and warrants to dilutive shares outstanding, which alters the ratio used to allocate earnings to common shareholders and participating securities for the purposes of calculating diluted EPS.