Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
Revenues	$ 1,149,890		$ 1,077,435	$ 889,065
Operating costs and expenses:
Costs of services provided	995,104		930,814	766,958
Selling, general and administrative	91,998		79,277	65,306
Other income:
Investment and interest	3,701		2,920	1,011
Income before income taxes	66,489		70,264	57,812
Income taxes	19,360		26,050	19,656
Net income	47,129		44,214	38,156
Per share data:
Basic earnings per common share (in dollars per share)	$ 0.68		$ 0.65	$ 0.57
Diluted earnings per common share (in dollars per share)	$ 0.67		$ 0.65	$ 0.56
Weighted average number of common shares outstanding:
Basic (in shares)	69,206		67,511	66,637
Diluted (in shares)	70,045		68,485	67,585
Comprehensive income:
Net income	47,129		44,214	38,156
Other comprehensive income:
Unrealized gain/(loss) on available for sale marketable securities, net of taxes	(78)	[1]	(216)	421
Total comprehensive income	$ 47,051		$ 43,998	$ 38,577

[1] All amounts are net of tax.