Credit Agreement (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2011	May 31, 2010
Credit Agreement
Maximum availability	$ 20,000	$ 20,000
Maximum borrowing capacity under letters of credit	12,500
Variable interest rate basis	Lender's prime rate or LIBOR
Spread on variable interest rate (as a percent)	1.00%
Annual commitment fees	60
New deposits in non-interest bearing accounts required to waive commitment fee	10,000
Outstanding letters of credit	724
Amount available under the Credit Agreement	19,276
Financial covenants
Maximum additional debt	20,000
Maximum asset sales	5,000
Maximum loans to employees	200
Maximum loans to subsidiaries that are not parties to the Credit Agreement	50,000
Additional financial covenants if outstanding obligations exceed $2 million
Amount of outstanding obligations that must be exceeded in order for additional financial covenants to apply	2,000
Initial tangible net worth	294,891
Percentage of consolidated net profit on a cumulative basis (as a percent)	75.00%
Number of consecutive quarters of net loss not allowable under the financial covenant	2
Maximum acquisitions	$ 25,000