Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Income Statement [Abstract]
Revenues	$ 355,356	$ 319,295	$ 710,602		$ 631,460
Operating costs and expenses:
Costs of services provided	304,217	275,815	608,153		543,186
Selling, general and administrative	25,124	22,240	51,887		44,286
Other income:
Investment and interest	242	803	749		1,184
Income before income taxes	26,257	22,043	51,311		45,172
Income tax provision	9,969	8,122	19,507		16,612
Net income	$ 16,288	$ 13,921	$ 31,804		$ 28,560
Per share data:
Basic earnings per common share (dollars per share)	$ 0.23	$ 0.20	$ 0.44		$ 0.41
Diluted earnings per common share (dollars per share)	$ 0.23	$ 0.20	$ 0.44		$ 0.40
Weighted average number of common shares outstanding:
Basic (shares)	71,657	70,440	71,563		70,381
Diluted (shares)	72,286	71,206	72,223		71,140
Comprehensive income:
Net income	$ 16,288	$ 13,921	$ 31,804		$ 28,560
Other comprehensive income:
Unrealized (loss) gain on available for sale marketable securities, net of taxes	(20)	6	(17)	[1]	7
Total comprehensive income	$ 16,268	$ 13,927	$ 31,787		$ 28,567

[1] All amounts are net of tax.