Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenues	$ 360,165	$ 320,099	$ 1,070,767	$ 951,559
Operating costs and expenses:
Costs of services provided	308,645	315,757	916,798	858,943
Selling, general and administrative	23,445	39,375	75,332	83,661
Other income (expense):
Investment and interest	(1,334)	(50)	(585)	1,134
Income (loss) before income taxes	26,741	(35,083)	78,052	10,089
Income tax provision (benefit)	9,655	(12,901)	29,162	3,711
Net income (loss)	$ 17,086	$ (22,182)	$ 48,890	$ 6,378
Per share data:
Basic earnings (loss) per common share (dollars per share)	$ 0.24	$ (0.31)	$ 0.68	$ 0.09
Diluted earnings (loss) per common share (dollars per share)	$ 0.24	$ (0.31)	$ 0.68	$ 0.09
Weighted average number of common shares outstanding:
Basic (shares)	72,009	70,671	71,714	70,479
Diluted (shares)	72,691	70,671	72,381	71,213
Comprehensive income:
Net income (loss)	$ 17,086	$ (22,182)	$ 48,890	$ 6,378
Other comprehensive income (loss):
Unrealized gain (loss) on available for sale marketable securities, net of taxes	198	(4)	181	3
Total comprehensive income (loss)	$ 17,284	$ (22,186)	$ 49,071	$ 6,381