Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 50,727	$ 46,415	$ 148,322	$ 128,134
Earnings allocated to participating securities - nonvested restricted shares	358	504	1,204	1,413
Earnings allocated to common shareholders, Basic	$ 50,369	$ 45,911	$ 147,118	$ 126,721
Weighted average common shares outstanding	71,803	72,427	72,256	72,370
Basic earnings per common share	$ 0.70	$ 0.63	$ 2.04	$ 1.75
Earnings allocated to common shareholders, Diluted	$ 50,369	$ 45,911	$ 147,118	$ 126,721
Dilutive effect of equity awards and warrants	0	5	1	4
Weighted average diluted common shares outstanding	71,803	72,432	72,257	72,374
Diluted earnings per common share	$ 0.70	$ 0.63	$ 2.04	$ 1.75
Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive.	0	0	0	5