Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Income Statement [Abstract]
Revenues	$ 312,165		$ 273,904
Operating costs and expenses:
Costs of services provided	267,371		235,191
Selling, general and administrative	22,046		20,790
Other income:
Investment and interest	381		1,034
Income before income taxes	23,129		18,957
Income taxes	8,490		4,003
Net income	14,639		14,954
Per share data:
Basic earnings per common share (dollars per share)	$ 0.21		$ 0.22
Diluted earnings per common share (dollars per share)	$ 0.21		$ 0.22
Weighted average number of common shares outstanding:
Basic (shares)	70,321		68,463
Diluted (shares)	71,072		69,361
Comprehensive income:
Net income	14,639		14,954
Other comprehensive income:
Unrealized gain on available for sale marketable securities, net of taxes	1	[1]	23
Total comprehensive income	$ 14,640		$ 14,977

[1] All amounts are net of tax.