Earnings Per Common Share (Details) - Basic and Diluted EPS - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income		$ 92,349	$ 82,064	$ 69,306
Net income applicable to non-vested restricted shares		(1,043)	(882)	(836)
Net income applicable to common shares		$ 91,306	$ 81,182	$ 68,470
Weighted-average common shares outstanding:
Weighted-average common shares outstanding (basic) (in shares)		79,797	77,059	74,484
Dilutive effect of common stock equivalents (in shares)		13	13	12
Weighted-average diluted common shares outstanding (in shares)		79,810	77,072	74,496
Basic EPS (in dollars per share)		$ 1.14	$ 1.05	$ 0.92
Diluted EPS (in dollars per share)		$ 1.14	$ 1.05	$ 0.92
Anti-dilutive shares not included in the computation of diluted EPS (in shares)	[1]	494	800	1,198

[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.