Stockholders' Equity - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Net income available to common shareholders	$ 15,161	$ 13,224	$ 27,456	$ 34,793
Denominator:
Basic weighted average shares outstanding	32,898,288	34,024,092	33,012,845	33,895,870
Effect of dilutive securities:
SARs and options	263,532	573,738	283,223	616,944
Restricted stock	145,643	186,710	156,746	160,614
Diluted weighted average shares outstanding	33,307,463	34,784,540	33,452,814	34,673,428
Basic earnings per share	$ 0.46	$ 0.39	$ 0.83	$ 1.03
Diluted earnings per share	$ 0.46	$ 0.38	$ 0.82	$ 1.00