Earnings Per Common Share (Details) - Basic and Diluted Earnings Per Common Share - 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, Basic and Diluted [Abstract]
Net income		$ 23,284	$ 18,549	$ 65,740	$ 54,713
Net income applicable to non-vested restricted shares		(226)	(242)	(703)	(697)
Net income applicable to common shares		$ 23,058	$ 18,307	$ 65,037	$ 54,016
Weighted-average common shares outstanding (in Shares)		77,106	74,341	77,038	74,270
Dilutive effect of common stock equivalents (in Shares)		13	11	13	12
Weighted-average diluted common shares outstanding (in Shares)		77,119	74,352	77,051	74,282
Basic earnings per common share (in Dollars per share)		$ 0.30	$ 0.25	$ 0.84	$ 0.73
Diluted earnings per common share (in Dollars per share)		$ 0.30	$ 0.25	$ 0.84	$ 0.73
Anti-dilutive shares not included in the computation of diluted earnings per common share (in thousands)	[1]	751	1,155	822	1,215

[1] This amount represents outstanding stock options for which the exercise price is greater than the average market price of the Company's common stock.