Stock-Based Compensation - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under Omnibus Incentive Plan				1,000,000
Stock options life, years	6 years	6 years 6 months
Stock options vesting period, years	3 years
Fair market value of fully vested shares as of the grant date	$ 25
Shares of common stock issued to non-employee directors	12,500	11,656	11,320
Stock-based compensation expense	1,102	1,196	1,258
Income tax benefit from stock-based compensation expense	386	419	440
Unrecognized stock-based compensation expense to be recognized in period, years	2 years
Unrecognized stock-based compensation expense	$ 1,375
Non-Qualified Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options life, years	10 years