United States Federal Statutory Tax Rate and Effective Tax Rate (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statutory Tax Rate and Effective Tax Rate [Line Items]
Statutory federal tax	$ 8,559,000	$ 9,688,000	$ 11,093,000
State income taxes, net of federal benefit	679,000	1,015,000	1,699,000
Domestic manufacturer deduction	(902,000)	(248,000)	(861,000)
FTC settlement	1,389,000	0	0
Other permanent differences	(190,000)	71,000	75,000
Research and development and jobs credits	(267,000)	(336,000)	0
Other state income tax benefits	(686,000)	(1,051,000)	0
Other	0	0	75,000
Income Tax Expense, Total	$ 8,582,000	$ 9,139,000	$ 12,081,000
Effective tax rate, Statutory federal tax	35.00%	35.00%	35.00%
Effective tax rate, State income taxes, net of federal benefit	2.80%	3.70%	5.40%
Effective tax rate, Domestic manufacturer deduction	(3.70%)	(0.90%)	(2.70%)
Effective tax rate, FTC settlement	5.70%
Effective tax rate, Other permanent differences	(0.80%)	0.30%	0.20%
Effective tax rate, Research and development and jobs credits	(1.10%)	(1.20%)
Effective tax rate, Other state income tax benefits	(2.80%)	(3.90%)
Effective tax rate, Other			0.20%
Effective tax rate, Total	35.10%	33.00%	38.10%