Stock-Based Incentive Plan - Status of Options Granted Under Long-Term Incentive Plan (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Shares Under Option
Shares Under Option, Outstanding, Beginning balance	612,050
Shares Under Option, Granted	114,000
Shares Under Option, Expired	0
Shares Under Option, Forfeited	(35,500)
Shares Under Option, Exercised	(17,334)	0	0
Share Under Option, Outstanding, Ending balance	673,216	612,050
Shares Under Options, Exercisable at December 31	393,662
Weighted Average Exercise Price Per Share [Abstract]
Weighted Average Exercise Price Per Share, Outstanding, Beginning balance	$ 19.41
Weighted Average Exercise Price Per Share, Granted	$ 18.78
Weighted Average Exercise Price Per Share, Expired	$ 0
Weighted Average Exercise Price Per Share, Forfeited	$ 17.06
Weighted Average Exercise Price Per Share, Exercised	$ 17.92
Weighted Average Exercise Price Per Share, Outstanding, Ending balance	$ 19.46	$ 19.41
Weighted Average Exercise Price Per Share, Exercisable at December 31, 2014	$ 21.07
Weighted Average Remaining Contractual Life, Outstanding at December 31, 2014	5 years 2 months
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2014	3 years 1 month
Aggregate Intrinsic Value, Outstanding at December 31, 2014	$ 1,201
Aggregate Intrinsic Value, Exercisable at December 31, 2014	$ 351