Note 9. Credit Facilities and Capital Leases (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Oct. 31, 2009
Long-term Line of Credit	$ 150,000,000		$ 60,000,000
Debt Instrument, Interest Rate Terms	The interest rate on outstanding loans under the agreement is between 3.00% and 3.75% above the LIBOR or an alternative base rate plus an applicable margin of between 2.00% and 2.75%.
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 August 1, 2015.
Debt and Capital Lease Obligations	14,800,000
Capital Lease Obligations, Current	4,654,000	4,005,000
Capital Lease Obligations, Noncurrent	10,163,000	6,265,000
Capital Lease Obligations	14,699,000	10,300,000
Capital Leases, Future Minimum Payments Due	15,529,000
Capital Leases, Future Minimum Payments, Interest Included in Payments	830,000
Leverage Ratio [Member]
Debt Instrument, Covenant Description	Leverage ratio (calculated as total debt divided by EBITDA) of not more than 3.0:1
Interest Coverage Ratio [Member]
Debt Instrument, Covenant Description	Interest coverage ratio (calculated as EBITDA divided by interest expense) of not less than 3.0:1
Current Ratio [Member]
Debt Instrument, Covenant Description	Current ratio (calculated as current assets divided by current liabilities) of not less than 1.10:1
Tangible Net Worth [Member]
Debt Instrument, Covenant Description	Tangible net worth of greater than $500 million
Amortization of Loan Origination Fees [Member]
Interest Expense, Debt	300,000
Commitment Fees on Credit Agreement [Member]
Interest Expense, Debt	$ 700,000