Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Income Statement [Abstract]
Revenues	$ 298,549	$ 272,681	$ 846,057		$ 800,396
Operating costs and expenses:
Costs of services provided	255,964	234,281	725,757		691,982
Selling, general and administrative	22,576	20,789	62,729		60,295
Other income:
Investment and interest	1,184	962	2,437		2,520
Income before income taxes	21,193	18,573	60,008		50,639
Income taxes	7,403	7,056	18,331		19,223
Net income	13,790	11,517	41,677		31,416
Per share data:
Basic earnings per common share (dollars per share)	$ 0.20	$ 0.17	$ 0.60		$ 0.47
Diluted earnings per common share (dollars per share)	$ 0.20	$ 0.17	$ 0.60		$ 0.46
Weighted average number of common shares outstanding:
Basic (shares)	69,706	67,651	68,926		67,344
Diluted (shares)	70,531	68,635	69,758		68,316
Comprehensive income:
Net income	13,790	11,517	41,677		31,416
Other comprehensive income:
Unrealized gain/(loss) on available for sale marketable securities, net of taxes	(1)	18	(84)	[1]	(172)
Total comprehensive income	$ 13,789	$ 11,535	$ 41,593		$ 31,244

[1] All amounts are net of tax.