Consolidated Income Statements (Unaudited) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated Income Statements [Abstract]
Revenues	$ 78,330	$ 66,935	$ 234,393	$ 210,883
Costs and expenses:
Operating costs (exclusive of depreciation and amortization)	53,807	45,714	160,675	143,298
Depreciation and amortization expense	2,207	1,646	6,280	4,767
Selling, general and administrative expense	16,794	16,869	51,484	54,125
Total costs and expenses	72,808	64,229	218,439	202,190
Operating income	5,522	2,706	15,954	8,693
Interest income and other income (expense), net	(341)	438	(99)	534
Interest expense	(263)	(238)	(758)	(720)
Income before income taxes	4,918	2,906	15,097	8,507
Income tax expense	(1,336)	(1,095)	(2,343)	(2,745)
Net income	$ 3,582	$ 1,811	$ 12,754	$ 5,762
Earnings per common share:
Basic	$ 0.10	$ 0.05	$ 0.34	$ 0.16
Diluted	$ 0.10	$ 0.05	$ 0.34	$ 0.16
Weighted-average number of common and common equivalent shares used in computing net income per common share:
Basic	37,107	36,743	37,002	36,722
Diluted	37,284	36,903	37,293	36,881