Earnings Per Common Share (Detail) - Basic and Diluted Earnings Per Common Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income		$ 82,064	$ 69,306	$ 79,306
Net income applicable to non-vested restricted shares		(882)	(836)	(1,107)
Net income applicable to common shares		$ 81,182	$ 68,470	$ 78,199
Weighted-average common shares outstanding:
Weighted-average common shares outstanding (basic)		77,059	74,484	73,984
Dilutive effect of common stock equivalents		13	12	10
Weighted-average diluted common shares outstanding		77,072	74,496	73,994
Basic earnings (loss) per common share (in dollars per share)		$ 1.05	$ 0.92	$ 1.06
Diluted earnings (loss) per common share (in dollars per share)		$ 1.05	$ 0.92	$ 1.06
Anti-dilutive shares not included in the computation of diluted earnings per common share (in Shares)	[1]	800	1,198	1,462

[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.