Note 9. Credit Facilities and Capital Leases (Detail) (USD $)	1 Months Ended	6 Months Ended				3 Months Ended	6 Months Ended
	Jul. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Oct. 10, 2011	Oct. 31, 2009	Mar. 31, 2012 Amortization of Loan Origination Fees [Member]	Jun. 30, 2012 Commitment Fees on Credit Agreement [Member]	Jun. 30, 2012 Leverage Ratio [Member]	Jun. 30, 2012 Interest Coverage Ratio [Member]	Jun. 30, 2012 Current Ratio [Member]	Jun. 30, 2012 Tangible Net Worth [Member]
Long-term Line of Credit		$ 100,000,000		$ 100,000,000	$ 60,000,000
Debt Instrument, Interest Rate Terms	The LIBOR margin increased from 2.75% - 3.50% under the current facility to 3.00% - 3.75% under the amended facility, and the base margin rate increased from 1.75%- 2.50% to 2.00% - 2.75%.	The interest rate on outstanding loans under the agreement is between 2.75% and 3.5% above the LIBOR or an alternative base rate plus an applicable margin of between 1.75% and 2.5%.
Debt Instrument, Fee		We are required to pay a standby fee of between 0.825% and 1.05% per annum on undrawn amounts under the revolving credit agreement.The credit facility is effective until September 30, 2014.
Interest Expense, Debt						200,000	400,000
Debt Instrument, Covenant Description								Leverage ratio (calculated as total debt divided by EBITDA) of not more than 3.0:1	Interest coverage ratio (calculated as EBITDA divided by interest expense) of not less than 3.0:1	Current ratio (calculated as current assets divided by current liabilities) of not less than 1.10:1	Tangible net worth of greater than $500 million
Line of Credit Facility, Maximum Borrowing Capacity	150,000,000	100,000,000
Debt and Capital Lease Obligations		13,600,000
Capital Lease Obligations, Current		4,552,000	4,005,000
Capital Lease Obligations, Noncurrent		9,054,000	6,265,000
Capital Lease Obligations		13,606,000	10,300,000
Capital Leases, Future Minimum Payments Due		14,389,000
Capital Leases, Future Minimum Payments, Interest Included in Payments		$ 783,000