Stock Options and Restricted Stock - Weighted Average Grant Date Fair Values of Options Granted (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Cash received from option exercises	$ 2,674	$ 2,344	$ 781
Total tax benefits realized for tax deductions from options exercised	2,797	2,002	405
Total intrinsic value of options exercised	9,145	6,654	1,468
Grant date fair value of options vested	144	226	310
Aggregate intrinsic value of vested options outstanding	$ 8,763	$ 17,467	$ 13,393