Acquisitions (Business Acquisition, Pro Forma Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Pro Forma Information, Description	The summary below (in thousands, except for per share data) presents pro forma consolidated results of operations for the six months ended June 30, 2012 and 2011 as if the acquisitions of HCP and Valesta occurred on January 1, 2010, and the acquisition of Apex Systems occurred on January 1, 2011. The pro forma financial information gives effect to certain adjustments, including: the amortization of intangible assets and interest expense on acquisition-related debt and changes in the management fees as a result of the acquisition. Acquisition-related costs are assumed to have occurred at the beginning of the year prior to acquisition. The pro-forma financial information is not necessarily indicative of the operating results that would have occurred if the acquisition had been consummated as of the date indicated, nor are they necessarily indicative of future operating results.
Revenues	$ 734,007	$ 620,762
Operating income	53,645	29,455
Net income	$ 24,171	$ 9,786
Basic earnings per share (in dollars per share)	$ 0.47	$ 0.19
Diluted earnings per share (in dollars per share)	$ 0.46	$ 0.19
Weighted average number of shares outstanding	51,788	51,102
Weighted average number of shares and dilutive shares outstanding	52,795	51,927

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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Description of the pro forma information, nature of adjustments made to historical information to arrive at pro forma amounts, amounts excluded from pro forma information, any material-nonrecurring items included in the pro forma information and limitations of pro forma disclosures.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, for the period as if the business combination or combinations had been completed at the beginning of a period.

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The weighted average number of shares or units and dilutive common stock or unit equivalents outstanding in the calculation of proforma diluted earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

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The weighted average number of shares (units) outstanding in the calculation of pro forma basic earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

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