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Acquisitions Acquisitions (Acquisition Costs, by Acquisition) (Details) - USD ($) $ in Thousands |  |  | 12 Months Ended
--- | --- | --- | ---
Jun. 05, 2015 | Apr. 14, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Business Acquisition [Line Items] |  |  |  |  |
Stock Issued During Period, Value, Acquisitions |  |  |  | $ 30,183 |
Stock Issued During Period, Shares, Acquisitions |  |  |  | 794,700 |
Payments of Merger Related Costs, Financing Activities |  |  | $ 16,814 | $ 0 | $ 691
Other Payments to Acquire Businesses |  |  | 4,780 | 0 | $ 0
Creative Circle [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Business Acquisition, Effective Date of Acquisition | Jun. 05, 2015 |  |  |  |
Business Acquisition, Name of Acquired Entity | Creative Circle, LLC |  |  |  |
Business Acquisition, Description of Acquired Entity | is headquartered in Los Angeles, California |  |  |  |
Business Combination, Reason for Business Combination | was purchased to expand the Company’s technical and creative staffing services |  |  |  |
Payments to Acquire Businesses, Gross | $ 540,000 |  |  |  |
Stock Issued During Period, Value, Acquisitions | $ 30,200 |  |  |  |
Stock Issued During Period, Shares, Acquisitions | 794,700,000 |  |  |  |
Business Acquisition Contingent Consideration At Fair Value Accrued Earn-Out | $ 13,800 |  |  |  |
Business Combination, Acquisition Related Costs |  |  |  | 5,700 |
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual |  |  |  | 167,200 |
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual |  |  |  | 22,900 |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Payments |  |  | 15,800 |  |
Payments of Merger Related Costs, Financing Activities |  |  | 13,800 |  |
Other Payments to Acquire Businesses |  |  | $ 2,000 |  |
LabResource [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Business Acquisition, Effective Date of Acquisition |  | Apr. 14, 2015 |  |  |
Business Acquisition, Name of Acquired Entity |  | LabResource B.V. |  |  |
Business Acquisition, Description of Acquired Entity |  | headquartered in Amsterdam, Netherlands |  |  |
Business Combination, Reason for Business Combination |  | expand the Company's life sciences staffing business in Europe |  |  |
Payments to Acquire Businesses, Gross |  | $ 12,700 |  |  |
Business Combination, Acquisition Related Costs |  | $ 400 |  |  |
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual |  |  |  | 7,700 |
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual |  |  |  | $ 1,000 |

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- Definition Payments that have taken place during the period in relation to liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy. + References No definition available. + Details
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- Definition With respect to a business combination completed during the period, this element provides a description of the business, other than the name, which may include the industry, size, products and other important information. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463 + Details
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- Definition Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e845-128460 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Acquisition Date -URI http://asc.fasb.org/extlink&oid=6919109 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e848-128460 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463 + Details
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- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e1043-128460 + Details
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- Definition This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463 + Details
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- Definition This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463 + Details
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- Definition This element represents a description of the primary reason for the business combination which may consist of general categories such as top-line growth, synergistic benefits, market share, and diversification and the more detailed factors that might apply. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463 + Details
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- Definition The cash outflow associated with other payments to acquire businesses including deposit on pending acquisitions and preacquisition costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 + Details
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- Definition The cash outflow for financing costs associated with business combinations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3291-108585 + Details
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- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585 + Details
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- Definition Number of shares of stock issued during the period pursuant to acquisitions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
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