Consolidated Income Statements (Unaudited) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Consolidated Income Statements [Abstract]
Revenues	$ 83,009	$ 77,513	$ 156,063	$ 143,948
Costs and expenses:
Operating costs (exclusive of depreciation and amortization)	56,425	51,922	106,868	97,584
Depreciation and amortization expense	2,198	1,572	4,073	3,121
Selling, general and administrative expense	17,779	18,493	34,690	37,256
Total costs and expenses	76,402	71,987	145,631	137,961
Operating income	6,607	5,526	10,432	5,987
Interest income and other income (expense), net	120	(246)	242	96
Interest expense	(255)	(241)	(495)	(482)
Income before income taxes	6,472	5,039	10,179	5,601
Income tax expense	(1,326)	(1,479)	(1,007)	(1,650)
Net income	$ 5,146	$ 3,560	$ 9,172	$ 3,951
Earnings per common share:
Basic	$ 0.14	$ 0.10	$ 0.25	$ 0.11
Diluted	$ 0.14	$ 0.10	$ 0.25	$ 0.11
Weighted-average number of common and common equivalent shares used in computing net income per common share:
Basic	36,971	36,734	36,948	36,711
Diluted	37,328	36,932	37,296	36,871