Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended				6 Months Ended		6 Months Ended			6 Months Ended			6 Months Ended
	Jun. 30, 2013 Event	Jul. 01, 2012	Jun. 30, 2013 Event	Jul. 01, 2012	Jun. 30, 2013 Restricted Stock [Member]	Dec. 31, 2012 Restricted Stock [Member]	Jun. 30, 2013 Stock Options [Member]	Dec. 31, 2012 Stock Options [Member]	Jun. 30, 2013 Employees Stock Purchase Plan [Member]	Jul. 01, 2012 Employees Stock Purchase Plan [Member]	Jun. 30, 2013 Employees Stock Purchase Plan [Member] Maximum [Member]	Jun. 30, 2013 Long-Term Plan [Member]	Jun. 30, 2013 Long-Term Plan [Member] Restricted Stock [Member]	Dec. 31, 2012 Long-Term Plan [Member] Restricted Stock [Member]	Jun. 30, 2013 Directors' Plan [Member]	Jun. 30, 2013 Directors' Plan [Member] Restricted Stock [Member]	Dec. 31, 2012 Directors' Plan [Member] Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Active Equity Incentive Plans Under Which Stock Awards Can Be Issued	2		2
Stock Based Compensation Plan Expiration Date												Apr. 08, 2020				Feb. 18, 2014
Maximum Shares of Common Stock Issuable Under Stock Compensation Plans											750,000	500,000			400,000
Vesting terms of outstanding restricted stock awards												3 years			2 years
Period required for vested options in the directors' plans to become exercisable							6 months
Period for exercising options under the plans			10 years
Restricted stock awarded under stock compensation plans					38,433	94,014							27,933	71,514		10,500	22,500
Exercisable options under the Directors' Plan							102,000	116,000
Unearned compensation related to restricted stock awards					$ 600,000	$ 1,300,000
Purchases of shares due to elections			10,899	11,611
Treasury stock purchases			281,000	272,000
Shares available for future grants									628,234			321,231			47,000
Purchase price of common stock under the ESPP									90.00%
Issued shares under stock compensation plans					157				21,700	22,870
Recognized total stock based compensation expense	$ 200,000	$ 800,000	$ 700,000	$ 1,200,000