Earnings Per Common Share (Details) - Basic and Diluted Earnings Per Common Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income		$ 25,267	$ 22,574	$ 43,229	$ 42,456
Net income applicable to non-vested restricted shares		(290)	(249)	(502)	(477)
Net income applicable to common shares		$ 24,977	$ 22,325	$ 42,727	$ 41,979
Weighted-average common shares outstanding (in Shares)		80,383	77,089	79,182	77,004
Dilutive effect of common stock equivalents (in Shares)		13	12	12	12
Weighted-average diluted common shares outstanding (in Shares)		80,396	77,101	79,194	77,016
Basic EPS (in Dollars per share)		$ 0.31	$ 0.29	$ 0.54	$ 0.55
Diluted EPS (in Dollars per share)		$ 0.31	$ 0.29	$ 0.54	$ 0.55
Anti-dilutive shares not included in the computation of diluted EPS (in Shares)	[1]	469	768	539	857

[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.