Stock Option Plan - Schedule of Analysis of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding, beginning of year, Shares	1,064,064
Granted, Shares	0
Exercised, Shares	(104,927)
Cancelled, Shares	(31,460)
Outstanding, end of year, Shares	927,677
Exercisable at end of year, Shares	358,597
Outstanding, beginning of year, Weighted-Average Ex. Price	$ 20.99
Granted, Weighted-Average Ex. Price	$ 0
Exercised, Weighted-Average Ex. Price	$ 13.69
Cancelled, Weighted-Average Ex. Price	$ 24.78
Outstanding, end of year, Weighted-Average Ex. Price	$ 21.69
Exercisable at end of year, Weighted-Average Ex. Price	$ 15.31
Outstanding, end of year, Weighted-Average Remaining Contractual Term (Years)	6 years 5 months 5 days
Exercisable at end of year, Weighted-Average Remaining Contractual Term (Years)	4 years 26 days
Outstanding, end of year, Aggregate Intrinsic Value	$ 20,118
Exercisable at end of year, Aggregate Intrinsic Value	$ 5,489