Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Income Statement [Abstract]
Revenues	$ 273,904		$ 260,607
Operating costs and expenses:
Costs of services provided	235,191		227,496
Selling, general and administrative	20,790		20,982
Other income:
Investment and interest	1,034		1,653
Income before income taxes	18,957		13,782
Income taxes	4,003		5,204
Net income	14,954		8,578
Per share data:
Basic earnings per common share (dollars per share)	$ 0.22		$ 0.13
Diluted earnings per common share (dollars per share)	$ 0.22		$ 0.13
Cash dividends per common share (dollars per share)	$ 0.16625		$ 0.16
Weighted average number of common shares outstanding:
Basic (shares)	68,463		67,084
Diluted (shares)	69,361		68,085
Comprehensive income:
Net income	14,954		8,578
Other comprehensive income:
Unrealized gain/(loss) on available for sale marketable securities, net of taxes	23	[1]	(173)
Total Comprehensive Income	$ 14,977		$ 8,405

[1] All amounts are net of tax.