ASGN (ASGN) 10-K29 Feb 162015 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2015	Feb. 22, 2016	Jun. 30, 2015
Entity Information [Line Items]
Entity Registrant Name	ON ASSIGNMENT INC
Entity Central Index Key	890,564
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		53,200,487
Entity Public Float			$ 1,888,588,488
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash	$ 23,869	$ 28,860
Accounts receivable, net of allowance of $6,682 and $4,404, respectively	354,808	277,146
Prepaid expenses and income taxes	12,686	13,308
Workerscompensationreceivable	13,238	13,370
Other current assets	9,607	2,310
Disposal Group, Including Discontinued Operation, Assets, Current	0	31,032
Total current assets	414,208	366,026
Property and equipment, net	53,196	44,311
Goodwill	874,906	512,060
Identifiable intangible assets, net	417,925	250,609
Other non-current assets	7,072	5,160
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	0	73,673
Total assets	1,767,307	1,251,839
Current liabilities:
Current portion of long-term debt	0	17,439
Accounts payable	9,132	7,925
Accrued payroll and contract professional pay	88,100	82,563
Workers' Compensation Liability, Current	15,020	15,564
Income taxes payable	673	340
Other current liabilities	47,425	20,729
Disposal Group, Including Discontinued Operation, Liabilities, Current	0	20,195
Total current liabilities	160,350	164,755
Long-term debt	755,508	394,418
Deferred income tax liabilities	61,539	48,075
Other long-term liabilities	5,116	7,937
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0	2,246
Total liabilities	$ 982,513	$ 617,431
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.01 par value, 1,000,000 shares authorized, no shares issued	$ 0	$ 0
Common stock, $0.01 par value, 75,000,000 shares authorized, 53,024,972 and 51,386,693 issued and outstanding, respectively	530	514
Paid-in capital	542,859	483,902
Retained earnings	249,567	154,562
Accumulated other comprehensive income (loss)	(8,162)	(4,570)
Total stockholders’ equity	784,794	634,408
Total liabilities and stockholders’ equity	$ 1,767,307	$ 1,251,839

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 6,682,000	$ 4,404,000
Stockholders’ equity:
Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred Stock, shares issued (in shares)	0	0
Preferred Stock, shares outstanding (in shares)	0	0
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	75,000,000	75,000,000
Common Stock, shares issued (in shares)	53,024,972	51,386,693
Common Stock: shares outstanding (in shares)	53,024,972	51,386,693

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenues	$ 2,065,008	$ 1,724,741	$ 1,523,101
Costs of services	1,386,263	1,167,306	1,068,226
Gross profit	678,745	557,435	454,875
Selling, general and administrative expenses	492,170	397,523	317,345
Amortization of intangible assets	34,467	22,130	20,943
Operating income	152,108	137,782	116,587
Interest expense, net	(26,444)	(12,730)	(13,931)
Write-off of loan costs	(3,751)	0	(14,958)
Income before income taxes	121,913	125,052	87,698
Provision for income taxes	50,491	51,557	36,558
Income from continuing operations	71,422	73,495	51,140
Gain on sale of discontinued operations, net of income taxes	25,703	0	30,840
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	525	3,689	2,532
Net income	$ 97,650	$ 77,184	$ 84,512
Basic earnings per common share:
Continuing operations	$ 1.37	$ 1.38	$ 0.96
Discontinued operations	0.50	0.06	0.62
Net income	1.87	1.44	1.58
Diluted earnings per common share:
Continuing operations	1.35	1.35	0.94
Discontinued operations	0.49	0.07	0.61
Net income	$ 1.84	$ 1.42	$ 1.55
Number of shares and share equivalents used to calculate earnings per share:
Basic (in shares)	52,259	53,437	53,481
Diluted (in shares)	53,005	54,294	54,555
Reconciliation of net income to comprehensive income:
Net income	$ 97,650	$ 77,184	$ 84,512
Changes in fair value of derivative, net of tax	122	86	193
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(3,714)	(4,772)	1,128
Comprehensive income	$ 94,058	$ 72,498	$ 85,833

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance (in shares) at Dec. 31, 2012		52,960,570
Balance at Dec. 31, 2012	$ 532,723	$ 530	$ 471,711	$ 61,687	$ (1,205)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		393,183
Exercise of common stock options	3,198	$ 3	3,195
Employee stock purchase plan (in shares)		203,200
Employee stock purchase plan	3,856	$ 2	3,854
Stock-based compensation expense	13,911
Vesting of restricted stock units and restricted stock awards (in shares)		369,572
Vesting of restricted stock units and restricted stock awards	(4,693)	$ 4	(4,697)
Tax deficiency from stock-based compensation	5,305		5,305
Fair value adjustment of derivatives, net of income tax	193				193
Translation adjustments	1,128				1,128
Net income (loss)	84,512			84,512
Balance (in shares) at Dec. 31, 2013		53,926,525
Balance at Dec. 31, 2013	640,133	$ 539	493,279	146,199	116
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		147,163
Exercise of common stock options	1,105	$ 1	1,104
Employee stock purchase plan (in shares)		207,805
Employee stock purchase plan	$ 5,253	$ 2	5,251
Stock repurchase and retirement (in shares)	(3,400,000)	(3,359,604)
Stock repurchase and retirement	$ (100,048)	$ (33)	31,194	68,821
Stock-based compensation expense	17,246
Vesting of restricted stock units and restricted stock awards (in shares)		464,804
Vesting of restricted stock units and restricted stock awards	(6,497)	$ 5	(6,502)
Tax deficiency from stock-based compensation	4,718		4,718
Fair value adjustment of derivatives, net of income tax	86				86
Translation adjustments	(4,772)				(4,772)
Net income (loss)	$ 77,184			77,184
Balance (in shares) at Dec. 31, 2014	51,386,693	51,386,693
Balance at Dec. 31, 2014	$ 634,408	$ 514	483,902	154,562	(4,570)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)	329,502	329,502
Exercise of common stock options	$ 3,472	$ 3	3,469
Employee stock purchase plan (in shares)		204,401
Employee stock purchase plan	$ 5,293	$ 2	5,291
Stock repurchase and retirement (in shares)	(43,000)	(89,174)
Stock repurchase and retirement	$ (3,819)	$ (1)	1,173	2,645
Stock-based compensation expense	23,471
Vesting of restricted stock units and restricted stock awards (in shares)		398,850
Vesting of restricted stock units and restricted stock awards	(8,823)	$ 4	(8,827)
Tax deficiency from stock-based compensation	$ 6,551		6,551
Stock Issued During Period, Shares, Acquisitions	794,700	794,700
Stock Issued During Period, Value, Acquisitions	$ 30,183	$ 8	30,175
Fair value adjustment of derivatives, net of income tax	122				122
Translation adjustments	(3,714)				(3,714)
Net income (loss)	$ 97,650			97,650
Balance (in shares) at Dec. 31, 2015	53,024,972	53,024,972
Balance at Dec. 31, 2015	$ 784,794	$ 530	$ 542,859	$ 249,567	$ (8,162)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities:
Net income	$ 97,650	$ 77,184	$ 84,512
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	(25,703)	0	(30,840)
Depreciation and amortization	51,569	38,296	29,882
Provision for Doubtful Accounts	10,486	7,047	1,787
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for deferred income taxes	11,549	15,948	4,111
Allocated Share-based Compensation Expense	22,018	16,199	14,411
Write off of Deferred Debt Issuance Cost	3,751	0	14,958
Gross excess tax benefits from stock-based compensation	(6,551)	(4,943)	(5,308)
Workers’ compensation and medical malpractice provision	2,117	3,321	5,956
Other Noncash Income (Expense)	(7,136)	(1,408)	1,853
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(53,775)	(45,361)	(20,155)
Prepaid expenses and income taxes	100	(8,304)	6,628
Increase (Decrease) in Income Taxes Payable	(7,679)	(8,023)	(5,759)
Accounts payable	1,684	(1,693)	(1,580)
Accrued payroll and contract professional pay	242	11,275	17,554
Increase (Decrease) in Workers' Compensation Liabilities	(901)	(2,192)	(2,348)
Deferred compensation	0	(20)	(9,980)
Other	3,800	(4,120)	8,548
Net cash provided by operating activities	117,493	96,022	110,524
Cash Flows from Investing Activities:
Cash paid for property and equipment	(24,689)	(19,729)	(16,531)
Cash paid for acquisitions, net of cash acquired	(552,777)	0	(110,700)
Proceeds from Divestiture of Businesses, Net of Cash Divested	115,440	0	59,899
Other	496	169	(1,023)
Net cash used in investing activities	(461,530)	(19,560)	(68,355)
Cash Flows from Financing Activities:
Principal payments of long-term debt	(516,125)	(148,688)	(456,275)
Proceeds from long-term debt	875,000	164,000	429,500
Proceeds from option exercises and employee stock purchase plan	6,591	6,358	7,054
Payment of employment taxes related to release of restricted stock awards	(8,823)	(6,498)	(7,600)
Gross excess tax benefits from stock-based compensation	6,551	4,943	5,308
Repurchase of common stock	(1,645)	(100,049)	0
Debt issuance or amendment costs	(23,890)	(467)	(6,938)
Payments of accrued earn-outs	0	(691)	(3,425)
Other	0	0	(14)
Net cash provided by (used in) financing activities	337,659	(81,092)	(32,390)
Effect of exchange rate changes on cash and cash equivalents	(1,467)	(1,006)	92
Net Increase (Decrease) in Cash and Cash Equivalents	(7,845)	(5,636)	9,871
Cash and Cash Equivalents at Beginning of Year (1)	31,714	37,350	27,479
Cash and Cash Equivalents at End of Year (1)	23,869	31,714	37,350
Supplemental Disclosure of Cash Flow Information
Income taxes	45,478	56,320	32,350
Interest	22,282	11,559	15,158
Non-Cash Investing and Financing Activities:
Equity consideration for acquisition	30,183	0	0
Proceeds from Stock Options Exercised	2,174	0	0
Acquisition of property and equipment through accounts payable	$ 989	$ 2,932	$ 594

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policie	Summary of Significant Accounting Policies Principles of Consolidation. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. Use of Estimates. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Revenue Recognition. Revenues from contract assignments, net of sales adjustments and discounts, are recognized when earned, based on hours worked by the Company’s contract professionals on a weekly basis. Permanent placement revenues are derived from direct hire and conversion fees. Direct hire fees relate to employment candidates that the Company directly places as permanent employees at a client organization. Conversion fees relate to contract professionals on assignment that convert to be permanent employees of the client. Direct hire and conversion fees are recognized as revenues when employment candidates or contract professionals begin permanent employment. The Company records a sales allowance against consolidated revenues, which is an estimate based on historical billing adjustment experience. The billing adjustment reserve includes an allowance for fallouts. Fallouts are permanent placements that do not complete the contingency period, which is typically 90 days or less. The Company includes reimbursed expenses, in revenues and the associated amounts of reimbursable expenses in costs of services. The Company records revenues on a gross basis as a principal or on a net basis as an agent depending on the arrangement. The key indicators as to whether it acts as a principal or an agent are whether the Company (i) has the direct contractual relationships with its customers, (ii) bears the risks and rewards of the transactions and (iii) has the discretion to select the contract professionals and establish their price. Costs of Services. Costs of services include direct costs of contract assignments consisting primarily of payroll, payroll taxes and benefit costs for the Company’s contract professionals. Costs of services also include assignment expenses, many of which are reimbursable by the client. Income Taxes. Income taxes are accounted for using the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that a portion of the deferred tax asset will not be realized. The Company makes a comprehensive review of its uncertain tax positions regularly. An uncertain tax position represents the Company’s expected treatment of a tax position taken in a filed return, or planned to be taken in a future tax return or claim that has not been reflected in measuring income tax expense for financial reporting purposes. In general, until these positions are sustained by the taxing authorities or statutes expire for the year that the position was taken, the Company does not recognize the tax benefits resulting from such positions and reports the tax effects as a liability for uncertain tax positions. Foreign Currency Translation. The functional currency of the Company’s foreign operations is their local currency, and as such, their assets and liabilities are translated into U.S. dollars at the rate of exchange in effect on the balance sheet date. Revenues and expenses are translated at the average rates of exchange prevailing during each monthly period. The related translation adjustments are recorded as cumulative foreign currency translation adjustments in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Gains and losses resulting from foreign currency transactions, which are not material, are included in SG&A expenses in the Consolidated Statements of Operations and Comprehensive Income. Cash and Cash Equivalents. The Company considers all highly liquid investments with a maturity of three months or less on the date of purchase to be cash equivalents. Allowance for Doubtful Accounts and Billing Adjustments. The Company estimates an allowance for doubtful accounts and an allowance for billing adjustments related to trade receivables based on an analysis of historical collection and billing adjustment experience. The Company applies bad debt percentages based on experience to the outstanding accounts receivable balances at the end of the period. The Company also analyzes specific reserves as needed. The allowance for billing adjustments includes a reserve for fallouts which is also based on historical experience. Receivables are written-off when deemed uncollectible. Property and Equipment. Property and equipment are stated at cost. Depreciation and amortization are provided using the straight-line method over the estimated useful lives of the related assets, generally three to five years. Leasehold improvements are amortized over the shorter of the life of the related asset or the remaining term of the lease. Costs associated with customized internal-use software systems that have reached the application development stage and meet recoverability tests are capitalized. Such capitalized costs include external direct costs utilized in developing or obtaining the applications and payroll and payroll-related expenses for employees who are directly associated with the application development. Business Combinations. The purchase price of an acquisition is allocated to the underlying assets acquired and liabilities assumed based upon their estimated fair values at the date of acquisition. To the extent the purchase price exceeds the fair value of the net identifiable tangible and intangible assets acquired and liabilities assumed, such excess is allocated to goodwill. The Company determines the estimated fair values after review and consideration of relevant information including discounted cash flows, quoted market prices and estimates made by management. Accordingly, these can be affected by contract performance and other factors over time, which may cause final amounts to differ materially from original estimates. The Company adjusts the preliminary purchase price allocation, as necessary, up to one year after the acquisition closing date if it obtains more information regarding asset valuations and liabilities assumed. Goodwill acquired in business combinations is assigned to the reporting unit(s) expected to benefit from the combination as of the acquisition date. Acquisition-related costs are recognized separately from the acquisition and are expensed as incurred. Goodwill and Identifiable Intangible Assets. Goodwill and indefinite-lived intangible assets (consisting entirely of trademarks) are tested for impairment on an annual basis as of October 31. Interim testing of goodwill and indefinite-lived intangible assets for impairment is also required whenever an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit or asset below its carrying amount. In order to test the trademarks for impairment, the Company estimates the fair value of the trademarks and compares such amount to their carrying value. The Company estimates the fair value of the trademarks using a projected discounted cash flow analysis, specifically a relief-from-royalty approach. The principal factors used in the discounted cash flow analysis requiring judgment are projected net sales, discount rate, royalty rate and terminal growth assumption. The royalty rates used in the analysis are based on royalty agreements and franchise agreements that have occurred in the staffing and services industries. Based upon the annual trademark impairment tests completed in 2015 , 2014 and 2013 , there were no indications of impairment of the trademarks, and no impairment charges. Intangible assets having finite lives are amortized over their useful lives and are tested for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Customer relationships are amortized using an accelerated method based on the annual cash flow observed in the initial valuation of the asset. Contractor relationships and non-compete agreements are amortized using the straight-line method. Goodwill is tested for impairment using a two-step process. The first step (Step 1) compares the fair value of a reporting unit to the reporting unit's carrying value. A reporting unit is generally an operating segment or one level below the operating segment level where a business operates and for which discrete financial information is available and reviewed by segment management. If after performing Step 1 of the goodwill impairment test, the fair value of equity of any reporting unit does not exceed its carrying value, the Company performs a second step (Step 2) of the goodwill impairment test for that reporting unit. Step 2 measures the amount of goodwill impairment by comparing the implied fair value of the respective reporting unit goodwill with the carrying value of that goodwill. The reporting unit goodwill impairment loss, if any, is measured as the amount by which the carrying value of goodwill exceeds the implied fair value of goodwill calculated in Step 2 of the goodwill impairment test. Impairment or Disposal of Long-Lived Assets. The Company evaluates long-lived assets, other than goodwill and identifiable intangible assets with indefinite lives, for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. An impairment loss is recognized when the sum of the undiscounted future cash flows is less than the carrying amount of the asset, in which case a write-down is recorded to reduce the related asset to its estimated fair value. There were no significant impairments of long-lived assets in 2015 , 2014 and 2013 . Workers’ Compensation Loss Reserves. The Company carries retention policies for its workers’ compensation liability exposures. In connection with these programs, the Company pays a base premium plus actual losses incurred, not to exceed certain stop-loss limits. The Company is insured for losses above these limits, both per occurrence and in the aggregate. The workers' compensation loss reserves are based upon an actuarial report obtained from a third party and determined based on claims filed and claims incurred but not reported. The Company accounts for claims incurred but not yet reported based on estimates derived from historical claims experience and current trends of industry data. Changes in estimates and differences in estimates and actual payments for claims are recognized in the period that the estimates changed or the payments were made. Contingencies. The Company records an estimated loss from a loss contingency when information available prior to issuance of its financial statements indicates it is probable that an asset has been impaired or a liability has been incurred at the date of the financial statements, and the amount of the loss can be reasonably estimated. Accounting for contingencies, such as legal settlements, and workers’ compensation matters, requires the Company to use judgment. Stock-Based Compensation. The Company records compensation expense for restricted stock awards and restricted stock units based on the fair market value of the awards on the date of grant. Compensation expense for performance-based awards is measured based on the amount of shares ultimately expected to vest, estimated at each reporting date based on management’s expectations regarding the relevant performance criteria. The Company accounts for stock options granted and employee stock purchase plan shares based on an estimated fair market value using a Black-Scholes option valuation model. This methodology requires the use of subjective assumptions including expected stock price volatility and the estimated life of each award. The fair value of equity-based compensation awards less the estimated forfeitures is amortized over the vesting period of the award. Concentration of Credit Risk. Financial instruments that potentially subject the Company to credit risks consist primarily of cash, cash equivalents and trade receivables. The Company places its cash and cash equivalents in low risk investments with quality credit institutions and limits the amount of credit exposure with any single institution above FDIC insured limits. Concentration of credit risk with respect to accounts receivable is limited because of the large number of geographically dispersed customers, thus spreading the trade credit risk. The Company performs ongoing credit evaluations to identify risks and maintains an allowance to address these risks. Advertising Costs. Advertising costs, which are expensed as incurred, were $3.6 million in 2015 , $4.8 million in 2014 , and $4.0 million in 2013 , and are included in SG&A expenses.

Accounting Standards Update (No

Accounting Standards Update (Notes)	12 Months Ended
Accounting Standards Update (Notes)	Dec. 31, 2015
Accounting Policies [Abstract]
New Accounting Pronouncements, Policy [Policy Text Block]	Accounting Standards Update In January 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20), Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items (“ASU No. 2015-01”). ASU No. 2015-01 eliminates from accounting principles generally accepted in the United States of America the concept of extraordinary items to simplify income statement presentation. Under the guidance an entity will no longer be able to segregate an extraordinary item from the results of operations, separately present an extraordinary item on the income statement, or disclose income taxes or earnings-per-share data applicable to an extraordinary item. The ASU is effective for all entities for reporting periods (including interim periods) beginning after December 15, 2015, and early adoption is permitted. The Company will adopt the standard effective January 1, 2016. The Company does not expect the adoption of this standard to have a material effect on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (“ASU 2015-03”). ASU No. 2015-03 requires that deferred loan costs be presented in the balance sheet as a direct deduction from the carrying amount of debt, consistent with debt discounts. The Company retrospectively adopted this new standard in 2015 (see "Note 6. Long-Term Debt )." In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (“ASU 2015-16”). ASU No. 2015-16 requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. The acquirer must record, in the same period's financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting has been completed at the acquisition date. This new guidance is effective for fiscal years beginning after December 15, 2015. The Company will adopt this standard on January 1, 2016. The Company does not expect the adoption this standard to have a material effect on its consolidated financial statements. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”). ASU No. 2015-17 requires that deferred tax assets and deferred tax liabilities be presented as noncurrent in a classified balance sheet. The Company adopted this new guidance as of December 31, 2015, and it is applied retrospectively for all periods presented. Adoption resulted in a $15.7 million decrease in deferred income tax assets and deferred income tax liabilities, and a decrease of $3.3 million current assets of discontinued operations and long-term liabilities of discontinued operations in our Consolidated Balance Sheet at December 31, 2014. Adoption had no impact on the Consolidated Statements of Operations and Comprehensive Income, see "Note 9. Income Taxes ."

Property and Equipment

Property and Equipment	12 Months Ended
Property and Equipment	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment.	Property and Equipment Property and equipment at December 31, 2015 and 2014 consisted of the following (in thousands): 2015 2014 Furniture, fixtures and equipment $ 14,445 $ 10,957 Computers and related equipment 33,121 21,741 Computer software 52,929 41,416 Leasehold improvements 10,551 5,637 Work-in-progress 4,139 11,943 115,185 91,694 Less -- accumulated depreciation (61,989 ) (47,383 ) $ 53,196 $ 44,311 Depreciation expense related to property and equipment was $16.8 million in 2015 , $12.3 million in 2014 and $7.2 million in 2013 , and is included in SG&A expenses. The Company has capitalized costs related to its various technology initiatives. At December 31, 2015 and 2014 , the net book value of the property and equipment related to software development was $15.7 million and $14.0 million , respectively, which included work-in-progress of $2.5 million and $9.0 million , respectively.

Acquisitions

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions	Acquisitions On June 5, 2015 , the Company acquired all of the outstanding shares of the holding company for Creative Circle. Creative Circle, which is headquartered in Los Angeles, California , was purchased to expand the Company’s technical and creative staffing services . The purchase price consisted of $540.0 million cash, $30.2 million of common stock ( 794,700 shares of the Company’s common stock), and estimated future contingent consideration which was valued at $13.8 million . Goodwill related to this acquisition totaled $358.0 million , and is deductible for income tax purposes. Acquisition expenses of approximately $5.7 million were expensed in 2015 and are included in SG&A. The results of operations for the acquisition have been combined with those of the Company from the acquisition date. Creative Circle revenues and income before income taxes included in the consolidated statement of operations and comprehensive income for the year-ended December 31, 2015 were $167.2 million and $22.9 million , respectively. On April 14, 2015 , the Company acquired all of the outstanding shares of LabResource B.V. ("LabResource") headquartered in Amsterdam, Netherlands for $12.7 million . LabResource was purchased to expand the Company's life sciences staffing business in Europe . Goodwill associated with this acquisition is not deductible for tax purposes. Acquisition expenses of approximately $0.4 million were expensed in 2015 and are included in SG&A. The results of operations for this acquisition have been combined with those of the Company from the acquisition date. LabResource revenues and income before income taxes included in the consolidated statement of operations and comprehensive income for 2015 were $7.7 million and $1.0 million , respectively. On December 5, 2013 , the Company acquired the holding company of CyberCoders , a provider of permanent placement services headquartered in Irvine, California. The primary reason for the acquisition was to expand the Company's permanent placement services. The purchase price was $96.6 million , comprised of $93.6 million in cash paid at closing and estimated future contingent consideration of $3.0 million , which is based on estimated financial performance of CyberCoders through 2015 (the maximum contingent consideration opportunity is $11.0 million ). Acquisition costs of approximately $1.5 million were expensed in 2013. Goodwill deductible for tax purposes is $10.3 million for this transaction. The results of operations for the acquisition have been combined with those of the Company from the acquisition date. Assets and liabilities of the acquired companies were recorded at their estimated fair values at the dates of acquisition. The excess purchase price over the fair value of net tangible assets and identifiable intangible assets acquired has been allocated to goodwill. The fair value assigned to identifiable intangible assets was determined primarily by using a discounted cash flow method. The Company's allocation of the purchase price of Creative Circle, LabResource and CyberCoders has been finalized and the following table summarizes the allocations (in thousands): 2015 Acquisitions 2013 Acquisition Creative Circle LabResource CyberCoders Cash $ 4,840 $ 187 $ 1,192 Accounts receivable 34,386 1,643 4,298 Prepaid expenses and other current assets 4,462 — 5,839 Property and equipment 5,077 12 3,327 Goodwill 358,029 6,449 69,018 Identifiable intangible assets 194,500 7,528 37,860 Other 651 — 915 Total assets acquired $ 601,945 $ 15,819 $ 122,449 Current liabilities $ 12,254 $ 1,482 $ 9,022 Other — 1,882 16,839 Total liabilities assumed 12,254 3,364 25,861 Total purchase price (1) (2) $ 589,691 $ 12,455 $ 96,588 (1) Excluding cash acquired and a $0.9 million adjustment for net working capital in excess of the targeted amount (thereby increasing the actual purchase price paid), the purchase price for Creative Circle was $584.0 million as described in the discussion above. (2) Excluding cash acquired and a $0.4 million adjustment for net working capital that was less than the targeted amount (thereby reducing the actual purchase price paid), the purchase price for LabResource was $12.7 million as described in the discussion above. The following table summarizes (in thousands) the allocation of the purchase price among the identifiable intangible assets for the acquisitions: Identifiable Intangible Asset Value 2015 Acquisitions 2013 Acquisition Useful life Creative Circle LabResource CyberCoders Contractor relationships 2 - 4 years $ 29,500 $ 947 $ 4,000 Customer relationships 2 - 10 years 90,700 5,421 860 Non-compete agreements 2 - 6 years 7,300 20 800 Favorable contracts 5 years 900 — — In-use software 6 years — — 18,900 Trademarks indefinite 66,100 1,140 13,300 Total identifiable intangible assets acquired $ 194,500 $ 7,528 $ 37,860 The summary below (in thousands, except for per share data) presents pro forma unaudited consolidated results of operations as if the acquisitions of Creative Circle and Lab Resource occurred on January 1, 2014, and the acquisition of CyberCoders occurred on January 1, 2012. The pro forma financial information gives effect to certain adjustments, including amortization of intangible assets, interest expense on acquisition-related debt, provision for income taxes, changes in the management fees, and increased number of common shares 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 acquisitions had been consummated as of the date indicated, nor are they necessarily indicative of future operating results. Year Ended December 31, 2015 2014 2013 Revenues $ 2,178,954 $ 1,960,851 $ 1,582,699 Income from continuing operations $ 79,159 $ 65,152 $ 54,947 Net income $ 105,387 $ 68,841 $ 88,319 Basic earnings per share: Income from continuing operations $ 1.50 $ 1.20 $ 1.03 Net income $ 2.00 $ 1.27 $ 1.65 Diluted earnings per share: Income from continuing operations $ 1.48 $ 1.18 $ 1.01 Net income $ 1.97 $ 1.25 $ 1.62 Number of shares and share equivalents used to calculate earnings per share: Basic 52,632 54,232 53,481 Diluted 53,411 55,124 54,555

Discontinued Operations

Discontinued Operations	12 Months Ended
Discontinued Operations	Dec. 31, 2015
Discontinued Operations [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	Discontinued Operations On February 1, 2015, the Company completed the sale of its Physician Segment for $123.0 million . The gain on the sale was $25.7 million (net of income taxes of $14.4 million ). The operating results of this segment are presented as discontinued operations in the consolidated statements of operations and comprehensive income for all periods presented. The consolidated balance sheet at December 31, 2014 separately states the assets and liabilities of the Physician Segment as discontinued operations. The following table is a reconciliation of the major classes of assets and liabilities of the Physician Segment that are presented separately in the consolidated balance sheet at December 31, 2014 (in thousands): December 31, 2014 As Previously Reported (1) Physician Segment As Adjusted Cash and cash equivalents $ 31,714 $ (2,854 ) $ 28,860 Accounts receivable, net 298,761 (21,615 ) 277,146 Prepaid expenses and income taxes 14,513 (1,205 ) 13,308 Workers' compensation and medical malpractice receivable 18,728 (5,358 ) 13,370 Other current assets 2,310 — 2,310 Current assets of discontinued operations — 31,032 31,032 Total current assets 366,026 — 366,026 Property and equipment, net 46,819 (2,508 ) 44,311 Goodwill 570,697 (58,637 ) 512,060 Identifiable intangible assets, net 262,569 (11,960 ) 250,609 Other non-current assets 5,728 (568 ) 5,160 Non-current assets of discontinued operations — 73,673 73,673 Total assets $ 1,251,839 $ — $ 1,251,839 Current portion of long-term debt $ 17,439 $ — $ 17,439 Accounts payable 8,876 (951 ) 7,925 Accrued payroll and contract professional pay 87,189 (4,626 ) 82,563 Workers’ compensation and medical malpractice loss reserves 29,135 (13,571 ) 15,564 Income taxes payable 340 — 340 Other current liabilities 21,776 (1,047 ) 20,729 Current liabilities of discontinued operations — 20,195 20,195 Total current liabilities 164,755 — 164,755 Long-term debt 394,418 — 394,418 Deferred income tax liabilities 48,842 (767 ) 48,075 Other long-term liabilities 9,416 (1,479 ) 7,937 Long-term liabilities of discontinued operations — 2,246 2,246 Total liabilities $ 617,431 $ — $ 617,431 (1) Retrospective adjustments have been made for the effects of early adopting Accounting Standards Updates No. 2015-3 and No. 2015-7 (see "Note 2. Accounting Standards Update"). Cash flows from discontinued operations are included in the accompanying consolidated statements of cash flows. The cash flows that are attributable to the Physician Segment are as follows (in thousands): Year Ended December 31, 2015 2014 2013 Net cash provided by (used in) operating activities $ (1,778 ) $ 836 $ (108 ) Net cash provided by (used in) investing activities: Cash received from sale of discontinued operations, net $ 115,440 $ — $ — Other (14 ) (308 ) (183 ) Total cash provided by (used in) investing activities $ 115,426 $ (308 ) $ (183 ) As of December 31, 2014, the Company closed its European retained search unit. Results for this European retained search unit, previously included in the Life Sciences Europe Segment, have been presented as discontinued operations in the consolidated statements of operations and comprehensive income for all periods presented. During 2013 the Company completed the sales of its Allied Healthcare and Nurse Travel divisions. Combined, these divisions were sold for $62.4 million in cash and generated gains totaling $30.8 million (net of income taxes of $19.5 million ). These divisions have been presented as discontinued operations in the consolidated statements of operations and comprehensive income for all periods presented. The following is a summary of the operating results of all of the Company's discontinued operations (in thousands): Year Ended December 31, 2015 2014 2013 Revenues $ 12,068 $ 137,166 $ 153,465 Costs of services 8,653 94,848 106,728 Gross profit 3,415 42,318 46,737 Selling, general and administrative expenses 2,385 33,078 38,991 Amortization of intangible assets 155 2,721 808 Operating income 875 6,519 6,938 Interest expense, net — — (2,456 ) Income before income taxes 875 6,519 4,482 Provision for income taxes 350 2,830 1,950 Income from discontinued operations, net of income taxes $ 525 $ 3,689 $ 2,532

Long-Term Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2015
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt At December 31, 2015 and 2014 , long-term debt consisted of the following (in thousands): 2015 2014 $150 million revolving credit facility, due June 2020 $ 50,000 $ — $825 million Term B loan facility, due June 2022 724,000 — $125 million revolving credit facility, repaid June 2015 — 76,000 Term A loan facility, repaid June 2015 — 158,813 Term B loan facility, repaid June 2015 — 180,312 774,000 415,125 Unamortized deferred loan costs (18,492 ) (3,268 ) $ 755,508 $ 411,857 On June 5, 2015, the Company entered into a new $975.0 million credit facility. The funds were used to repay the old credit facility and to fund the cash portion of the purchase of Creative Circle (see "Note 4. Acquisitions" ). The new facility consists of (i) an $825.0 million seven-year term B loan facility and (ii) a $150.0 million five-year revolving loan facility. Under terms of the new facility, the Company has the ability to increase the principal amount of the loan facilities. Borrowings under the term B loan bear interest at LIBOR (floor of 75 basis points), plus 3.0 percent and borrowings under the revolving credit facility bear interest at LIBOR (or the bank’s base rate) plus 0.75 to 2.5 percent depending on leverage levels. A commitment fee of 0.25 to 0.40 percent is payable on the undrawn portion of the revolving credit facility. At December 31, 2015 , the weighted average interest rate was 3.7 percent. Under terms of the credit facility, the Company is required to make minimum quarterly payments of $2.1 million . Through December 31, 2015 , the Company repaid $101.0 million and, as a result, the next required payments will be on the maturity dates. The Company is also required to make mandatory prepayments, subject to specified exceptions, from excess cash flow and with the proceeds of asset sales, debt issuances and specified other events. The Company's obligations under the credit facility are guaranteed by substantially all of its direct and indirect domestic subsidiaries and are secured by a lien on substantially all of the Company's tangible and intangible property and by a pledge of all of the equity interests in its direct and indirect domestic subsidiaries. The credit facility includes various restrictive covenants including the maximum ratio of consolidated funded debt to consolidated EBITDA ( 4.50 to1.00 as of December 31, 2015 decreasing to 3.25 to 1.00 on March 31, 2018). The credit facility also contains certain customary limitations including, among other terms and conditions, the Company's ability to incur additional indebtedness, engage in mergers and acquisitions, and declare dividends. At December 31, 2015 , the Company had a ratio of consolidated funded debt to consolidated EBITDA of 3.02 to 1.00. At December 31, 2015 the Company was in compliance with all of its debt covenants and had $96.5 million of borrowing available under the revolving credit facility.

Goodwill and Identifiable Asset

Goodwill and Identifiable Assets	12 Months Ended
Goodwill and Identifiable Assets	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Identifiable Intangible Assets	Goodwill and Other Identifiable Intangible Assets The changes in the carrying amount of goodwill for the years ended December 31, 2015 and 2014 are as follows (in thousands): Apex Oxford Total Balance as of December 31, 2013 $ 289,712 $ 224,714 $ 514,426 Translation adjustment (1,761 ) (605 ) (2,366 ) Balance as of December 31, 2014 287,951 224,109 512,060 Creative Circle Acquisition 358,029 — 358,029 LabResource Acquisition — 6,449 6,449 Translation adjustment (1,363 ) (269 ) (1,632 ) Balance as of December 31, 2015 $ 644,617 $ 230,289 $ 874,906 As of December 31, 2015 and 2014 , the Company had the following acquired intangible assets (in thousands): 2015 2014 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Subject to amortization: Customer relationships 2 - 10 years $ 196,472 $ 74,640 $ 121,832 $ 101,141 $ 53,434 $ 47,707 Contractor relationships 2 - 5 years 69,764 40,124 29,640 39,332 32,021 7,311 Non-compete agreements 2 - 7 years 10,874 3,163 7,711 3,654 1,922 1,732 Favorable contracts 5 years 900 172 728 — — — In-use software 6 years 18,900 6,516 12,384 18,900 3,366 15,534 296,910 124,615 172,295 163,027 90,743 72,284 Not subject to amortization: Trademarks 245,630 — 245,630 178,325 — 178,325 Total $ 542,540 $ 124,615 $ 417,925 $ 341,352 $ 90,743 $ 250,609 Amortization expense for intangible assets with finite lives wa s $34.5 million i n 2015 , $22.1 million in 2014 and $20.9 million in 2013 . Estimated amortization for each of the next five years and thereafter are as follows (in thousands): 2016 $ 39,657 2017 33,029 2018 28,904 2019 22,008 2020 14,496 Thereafter 34,201 $ 172,295

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company leases its facilities and certain office equipment under operating leases, which expire at various dates through 2025. Certain leases contain rent escalations or renewal options or both. Rent expense for all significant leases is recognized on a straight-line basis. The balance of the deferred rent liability reflected in other current liabilities in the accompanying consolidated balance sheets was $0.5 million and $ 0.3 million at December 31, 2015 and 2014 , respectively, and the balance reflected in other long-term liabilities was $4.3 million and $4.0 million , at December 31, 2015 and 2014 , respectively. The following is a summary of specified contractual cash obligation payments by the Company, as of December 31, 2015 (in thousands): Operating Leases Related Party Leases Total 2016 $ 18,369 $ 1,190 $ 19,559 2017 15,533 1,169 16,702 2018 12,994 1,302 14,296 2019 9,989 1,282 11,271 2020 7,573 1,314 8,887 Thereafter 11,854 5,346 17,200 Total $ 76,312 $ 11,603 $ 87,915 Rent expense is included in SG&A expenses and was $21.6 million , $17.6 million and $15.4 million in 2015 , 2014 and 2013 , respectively. The Company has entered into various non-cancelable operating leases, primarily related to its facilities and certain office equipment used in the ordinary course of business. As a result of the Apex Systems acquisition, the Company leases two properties owned by related parties. Rent expense for these two properties wa s $1.3 million for each of the years 2015 , 2014 and 2013 . The Company carries large retention policies for its workers’ compensation liability exposures. The workers' compensation loss reserves are based upon an actuarial report obtained from a third party and determined based on claims filed and claims incurred but not reported. The Company accounts for claims incurred but not yet reported based on estimates derived from historical claims experience and current trends of industry data. Changes in estimates, differences in estimates, and actual payments for claims, are recognized in the period that the estimates changed or the payments were made. The workers' compensation loss reserves were approximately $1.8 million and $2.2 million , net of anticipated insurance and indemnification recoveries of $13.2 million and $13.4 million , at December 31, 2015 and 2014 , respectively. The Company has unused stand-by letters of credit outstanding to secure obligations for workers’ compensation claims with various insurance carriers. The unused stand-by letters of credit at December 31, 2015 and December 31, 2014 were $3.5 million and $3.2 million , respectively. The Company is subject to contingent consideration agreements entered into in connection with certain of its acquisitions. If the acquired businesses meet predetermined targets, the Company is obligated to make additional cash payments in accordance with the terms of such contingent consideration agreements, see "Note 15. Fair Value Measurements." Certain employees participate in the Company’s Change in Control Severance Plan, or have separate agreements that provide for certain benefits in the event of termination at the Company's convenience or following a change in control, as defined by the plan or agreement. Generally, these benefits are based on the employee’s length of service and position with the Company and include, severance, continuation of health insurance and in certain cases acceleration of vesting of option or stock awards. Legal Proceedings The Company is involved in various legal proceedings, claims and litigation arising in the ordinary course of business. Based on the facts currently available, the Company does not believe that the disposition of matters that are pending or asserted will have a material effect on its consolidated financial statements.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The provision for income taxes consists of the following (in thousands): Year Ended December 31, 2015 2014 2013 Current: Federal $ 31,295 $ 28,581 $ 26,284 State 5,837 5,060 4,910 Foreign 2,048 2,181 1,204 39,180 35,822 32,398 Deferred: Federal & State 11,520 15,991 4,244 Foreign (209 ) (256 ) (84 ) 11,311 15,735 4,160 $ 50,491 $ 51,557 $ 36,558 Income from continuing operations before income taxes consists of the following (in thousands): Year Ended December 31, 2015 2014 2013 United States $ 116,011 $ 122,496 $ 82,970 Foreign 5,902 2,556 4,728 $ 121,913 $ 125,052 $ 87,698 The components of deferred tax assets (liabilities) are as follows (in thousands): December 31, 2015 2014 Intangibles $ (70,588 ) $ (59,226 ) Depreciation expense (14,369 ) (13,405 ) Allowance for doubtful accounts 2,607 2,027 Employee related accruals 7,573 7,240 Workers’ compensation and medical malpractice loss reserves 720 4,068 Stock-based compensation 7,354 3,022 Other 5,061 7,286 Net operating loss carryforwards 1,147 1,260 Valuation allowance (1,044 ) (1,114 ) $ (61,539 ) $ (48,842 ) The table above includes non-current deferred income tax liabilities of $0.8 million for the Physician Segment as of December 31, 2014 (see "Note 5. Discontinued Operations" ). The reconciliation between the amount computed by applying the U.S. federal statutory tax rate of 35.0 percent to income before income taxes and the income tax provision is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Income tax provision at the statutory rate $ 42,669 $ 43,768 $ 30,694 State income taxes, net of federal benefit 4,559 4,674 3,807 Disallowed meals and entertainment expenses 1,718 1,608 1,592 Other 1,545 1,507 465 $ 50,491 $ 51,557 $ 36,558 As of December 31, 2015 , the Company had no federal net operating losses, $8.8 million of state net operating losses, and $4.9 million of foreign net operating losses. The state net operating losses can be carried forward up to 20 years and begin expiring in 2016. The foreign net operating losses in the United Kingdom and Spain can be carried forward indefinitely. The Company has a valuation allowance of approximately $1.0 million related to net operating loss carryforwards at December 31, 2015 and 2014. The Company has not provided deferred income taxes on $11.0 million of undistributed earnings of its foreign subsidiaries as of December 31, 2015 since the Company intends to reinvest these earnings indefinitely. Those earnings are considered to be indefinitely reinvested; accordingly, no provision for U.S. federal and state income taxes has been provided thereon. Upon repatriation of those earnings, in the form of dividends or otherwise, the Company would be subject to both U.S. income taxes (subject to an adjustment for foreign tax credits) and withholding taxes payable to the various foreign countries. Determination of the amount of unrecognized deferred U.S. income tax liability is not practicable due to the complexities associated with its hypothetical calculation; however, unrecognized foreign tax credit carryforwards would be available to reduce some portion of the U.S. liability. The Company had gross deferred tax assets of $29.2 million and $24.1 million , and gross deferred tax liabilities of $89.7 million and $71.4 million , at December 31, 2015 and 2014 , respectively. Management has determined the gross deferred tax assets are realizable, with the exception of foreign net operating losses discussed above. At December 31, 2015 , 2014 and 2013 , there were $0.8 million to $0.9 million of unrecognized tax benefits that if recognized would affect the annual effective tax rate. The gross unrecognized tax benefit is carried in other long-term liabilities. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. The amount of interest and penalties recognized in the financial statements is not significant. The Company believes that there will be no significant increases or decreases to unrecognized tax benefits within the next 12 months. The following is a reconciliation of the total amounts of unrecognized tax benefits (in thousands): Year Ended December 31, 2015 2014 2013 Unrecognized tax benefit beginning of year $ 848 $ 979 $ 376 Gross increases - tax positions in prior year — 126 1,240 Gross decreases - tax positions in prior year (34 ) — (177 ) Lapse of the statute of limitations — (131 ) — Discontinued operations — (126 ) (460 ) Unrecognized tax benefit end of year $ 814 $ 848 $ 979 The Company is subject to taxation in the United States and various states and foreign jurisdictions. The Company remains subject to U.S. Federal income tax examinations for 2012 and subsequent years. For major U.S. states, with few exceptions, the Company remains subject to examination for 2011 and subsequent years. Generally, for the foreign tax jurisdictions, the Company remains subject to examination for 2011 and subsequent years.

Earnings per share

Earnings per share	12 Months Ended
Earnings per share	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings per share	Earnings per Share Basic earnings per share are computed using the weighted average number of shares outstanding and diluted earnings per share are computed using the weighted average number of shares and dilutive share equivalents (consisting of incentive stock options, non-qualified stock options, restricted stock units and employee stock purchase plan contributions) outstanding during the periods using the treasury stock method. The following is a reconciliation of the shares used to compute basic and diluted earnings per share (in thousands): Year Ended December 31, 2015 2014 2013 Weighted average number of common shares outstanding used to compute basic earnings per share 52,259 53,437 53,481 Dilutive effect of stock-based awards 746 857 1,074 Number of shares used to compute diluted earnings per share 53,005 54,294 54,555 There were no significant share equivalents outstanding as of December 31, 2015, 2014 and 2013 that were anti-dilutive when applying the treasury stock method.

Stockholders' Equity (Notes)

Stockholders' Equity (Notes)	12 Months Ended
Stockholders' Equity (Notes)	Dec. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Treasury Stock [Text Block]	Stockholders' Equity On July 21, 2014, the Board of Directors approved a program authorizing the Company to repurchase up to $100.0 million of the Company’s common stock. The authorization was effective August 4, 2014. During 2014, the Company repurchased 3.4 million shares of its common stock under this program at a cost of $100 million . All shares repurchased under this program were retired. This resulted in a reduction of $31.2 million in paid-in capital and a reduction of $68.8 million in retained earnings. On January 16, 2015, the Company's Board of Directors approved a new $100.0 million share repurchase program. During 2015, the Company repurchased 43,000 shares of its common stock at a cost of $1.6 million . All shares repurchased under this program were retired, which resulted in a reduction of $0.4 million in paid-in capital and a reduction of $1.2 million in retained earnings. This repurchase program is effective through February 23, 2017, and as of December 31, 2015, the remaining authorization for share repurchases is $98.4 million . On June 5, 2015, the Company issued 794,700 shares of its common stock valued at $30.2 million , in connection with the acquisition of Creative Circle. The Company's stock-based compensation plans accept shares of the Company's common stock as payment for the exercise price of stock options. During the three months ended December 31, 2015 , we received 46,174 shares, with a $2.2 million value, as payment for the exercise of stock options. Those shares were retired upon receipt.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Notes)	12 Months Ended
Accumulated Other Comprehensive Income (Notes)	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Income (Loss) The components of accumulated other comprehensive income (loss) were as follows (in thousands): Foreign currency translation adjustment Changes in fair value of derivative, net of tax Accumulated other comprehensive income (loss) Balance at December 31, 2012 $ (804 ) $ (401 ) $ (1,205 ) Other comprehensive income 1,128 193 1,321 Balance at December 31, 2013 324 (208 ) 116 Other comprehensive income (4,772 ) 86 (4,686 ) Balance at December 31, 2014 (4,448 ) (122 ) (4,570 ) Other comprehensive income (3,714 ) 122 (3,592 ) Balance at December 31, 2015 $ (8,162 ) $ — $ (8,162 )

Stock-based Compensation_ Incen

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan	Stock-Based Compensation and 401(k) Retirement Savings Plan The Company believes that stock-based compensation aligns the interests of its employees and directors with those of its stockholders. Stock-based compensation provides incentives to retain and motivate executive officers and key employees responsible for driving Company performance and maintaining important relationships that contribute to the growth of the Company. In 2015, the Company issued shares for restricted stock units ("RSUs"), stock options, and a stock award. Stock-based compensation expense is included in SG&A expenses in the accompanying consolidated statements of operations and comprehensive income and was classified as follows (in thousands): Year Ended December 31, 2015 2014 2013 Continuing operations $ 22,018 $ 15,623 $ 13,533 Discontinued operations — 576 878 Total $ 22,018 $ 16,199 $ 14,411 The Company recognized an income tax benefit for stock-based compensation arrangements of $6.6 million , $4.7 million and $5.1 million in 2015 , 2014 and 2013 , respectively. As of December 31, 2015 , there were 2,546,962 shares available for issuance under the Company's stock- based compensation plans. Restricted Stock Units The fair value of each RSU is based on the fair market value of the awards on the grant date and the Company records compensation expense based on this value, net of a forfeiture rate. The forfeiture rate estimates the number of awards that will eventually vest and is based on historical vesting patterns for RSUs. A summary of the status of the Company’s unvested RSUs as of December 31, 2015 and changes during the year then ended are presented below: Service Conditions Performance and Service Conditions Total Weighted Average Grant-Date Fair Value Per Unit Unvested RSUs outstanding at December 31, 2014 705,373 381,188 1,086,561 $ 24.88 Granted 213,649 712,108 925,757 $ 40.49 Market value share count adjustment for liability awards — 18,619 18,619 $ 35.09 Vested (423,280 ) (204,936 ) (628,216 ) $ 24.76 Forfeited (30,373 ) (25,728 ) (56,101 ) $ 31.38 Unvested RSUs outstanding at December 31, 2015 465,369 881,251 1,346,620 $ 36.31 Unvested and expected to vest RSUs outstanding at December 31, 2015 437,699 826,620 1,264,319 $ 36.05 The total number of shares vested in the table above includes 229,366 shares surrendered by the employees to the Company for payment of income taxes. The surrendered shares are available for issuance under the Plan. The weighted-average grant-date fair value of RSUs granted during 2015, 2014 and 2013 was $40.49 , $33.66 and $26.17 per award, respectively. The total intrinsic value of RSUs that vested during 2015, 2014 and 2013 , was $24.3 million , $21.3 million and $15.0 million , respectively. As of December 31, 2015 , there was unrecognized compensation expense of $30.9 million related to unvested RSUs based on awards that are expected to vest. The unrecognized compensation expense is expected to be recognized over a weighted-average period of two years. Liability Awards Liability awards have a performance component and vest over one to three years. The performance goals are approved by the Compensation Committee of the Company’s Board of Directors. The Company classifies these awards as liabilities until the number of shares is determined, in accordance with the grant. The number of shares is determined by dividing the final award liability balance by the Company’s closing stock price on the settlement dates. This liability is included in other accrued expenses in the accompanying Consolidated Balance Sheets . The following table summarizes the balance of liability awards and changes during the years presented (in thousands): 2015 2014 2013 Balances of liability awards at beginning of year $ 1,453 $ 2,500 $ 2,000 Granted — 500 1,000 Settled (1,453 ) (1,497 ) (500 ) Canceled — (50 ) — Balance of liability awards end of year $ — $ 1,453 $ 2,500 There was no expense related to liability awards during 2015 and the expense in 2014 and 2013 was $0.5 million and $1.0 million , respectively. There was no unrecognized compensation expense for liability awards as of December 31, 2015. Stock Options Subsequent to 2012 the Company has not granted any stock options. The fair value of stock option grants was estimated on the grant date using the Black-Scholes option pricing model. The Company records compensation expense based on this value, net of a forfeiture rate. The forfeiture rate estimates the number of awards that will eventually vest and is based on historical vesting patterns for stock options. The following summarizes pricing and term information for options outstanding as of December 31, 2015 : Options Outstanding Options Exercisable Number Outstanding at Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price Number Exercisable at Weighted Average Exercise Price Range of Exercise Prices December 31, 2015 December 31, 2015 $ 4.44 - $ 8.26 73,901 4.0 $ 6.96 73,305 $ 6.95 $ 10.46 - $ 11.75 61,885 4.3 $ 10.88 60,755 $ 10.89 $ 12.90 - $ 12.90 120,000 1.1 $ 12.90 120,000 $ 12.90 $ 13.31 - $ 13.58 25,600 1.4 $ 13.33 25,506 $ 13.32 $ 16.51 - $ 16.51 75,000 6.7 $ 16.51 60,937 $ 16.51 $ 4.44 - $ 16.51 356,386 3.5 $ 12.11 340,503 $ 11.94 The following table is a summary of stock option activity during 2015 : Incentive Stock Options Non- Qualified Stock Options Total Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding at December 31, 2014 4,267 690,614 694,881 $ 11.33 3.5 $ 15,189,000 Exercised (4,267 ) (325,235 ) (329,502 ) $ 10.54 Canceled — (8,993 ) (8,993 ) $ 9.81 Outstanding at December 31, 2015 — 356,386 356,386 $ 12.11 3.5 $ 11,705,000 Vested and Expected to Vest at December 31, 2015 — 356,386 356,386 $ 12.11 3.5 $ 11,705,000 Exercisable at December 31, 2015 — 340,503 340,503 $ 11.94 3.3 $ 11,241,000 The total intrinsic value of options exercised during 2015, 2014 and 2013 was $10.9 million , $3.9 million , and $7.6 million , respectively. Employee Stock Purchase Plan The On Assignment 2010 Employee Stock Purchase Plan, as amended ("ESPP") allows eligible employees to purchase common stock of the Company at a 15 percent discount to the market price as stipulated by the plan. Under the ESPP, 3,500,000 shares of common stock were reserved for issuance when it was approved on June 3, 2010 by the Company's stockholders. Shares of common stock are transferred to participating employees at the conclusion of each six-month offering period, which ends on the last business day of the month in March and September each year. Compensation expense is measured using a Black-Scholes option-pricing model. The table below presents the average fair value per share of shares purchased, and the compensation expense under the ESPP (dollars in thousands, except per share amounts): Year Ended December 31, Average fair value per share Shares Expense 2015 $7.77 204,401 $ 1,586 2014 $8.35 207,805 $ 1,756 2013 $7.16 203,200 $ 1,195 401(k) Retirement Savings Plan The Company maintains various 401(k) retirement savings plans for the benefit of eligible employees. Under terms of these plans, eligible employees are able to make contributions to these plans on a tax-deferred basis. The Company makes matching contributions, some of which are discretionary. The Company made contributions to the 401(k) plans of $7.6 million , $7.5 million and $6.0 million for the years ended December 31, 2015 , 2014 and 2013 , respectively.

Business Segments

Business Segments	12 Months Ended
Business Segments	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	Business Segments On Assignment provides services through two operating segments, the Apex Segment and the Oxford Segment, with each addressing different sectors of the professional staffing market with distinct business models attuned to those sectors. Businesses in the Apex Segment predominately serve markets with a large and local talent pool, and provide a full range of skills through a network of local offices where clients most value relationship, speed, reliability and price. The Apex Segment provides a broad spectrum of technical, scientific and creative professionals for contract, contract-to-hire and permanent placement positions to Fortune 1000 and mid-market clients across the United States. Our businesses in this segment include Apex Systems, Lab Support and Creative Circle. Businesses in the Oxford Segment predominately serve markets with higher-end, specialized skills through a combination of national recruiting centers and local offices where clients most value the unique skill of the candidate and speed of response. The Oxford Segment provides specialized, niche staffing and consulting services in select skill and geographic markets. Our businesses in this segment include Oxford, CyberCoders and Life Sciences Europe. The Company’s management evaluates the performance of each segment primarily based on revenues, gross profit and operating income. The information in the following tables is derived directly from the segments’ internal financial reporting used for corporate management purposes. The Company's management does not evaluate, manage or measure performance of segments using asset information, and such information is not readily available. Accordingly, assets by reportable segment are not disclosed. The following tables present revenues, gross profit, operating income and amortization by reportable segment (in thousands): Year ended December 31, 2015 Apex Oxford Corporate (1) Total Revenues $ 1,487,042 $ 577,966 $ — $ 2,065,008 Gross Profit 437,507 241,238 — 678,745 Operating income 151,559 70,385 (69,836 ) 152,108 Amortization 28,371 6,096 — 34,467 Year ended December 31, 2014 Apex Oxford Corporate (1) Total Revenues $ 1,190,052 $ 534,689 $ — $ 1,724,741 Gross Profit 335,322 222,113 — 557,435 Operating income 121,334 70,193 (53,745 ) 137,782 Amortization 16,356 5,765 9 22,130 Year ended December 31, 2013 Apex Oxford Corporate (1) Total Revenues $ 1,059,993 $ 463,108 $ — $ 1,523,101 Gross Profit 294,611 160,264 — 454,875 Operating income 98,588 66,118 (48,119 ) 116,587 Amortization 19,524 1,329 90 20,943 (1) Corporate expenses primarily consist of compensation for our corporate staff which includes personnel that have a shared service role and support certain of our businesses. It also includes all of the Company's acquisition, integration and strategic planning expenses; depreciation expense for corporate facilities; and public company expenses. The following table presents revenues by type (in thousands): Year Ended December 31, 2015 2014 2013 Revenues: Assignment $ 1,947,001 $ 1,641,706 $ 1,500,157 Permanent placement 118,007 83,035 22,944 $ 2,065,008 $ 1,724,741 $ 1,523,101 The Company operates internationally, with operations in the United States, Europe and Canada. The following table presents revenues by geographic location (in thousands): Year Ended December 31, 2015 2014 2013 Revenues: Domestic $ 1,972,888 $ 1,643,598 $ 1,446,805 Foreign 92,120 81,143 76,296 $ 2,065,008 $ 1,724,741 $ 1,523,101 The following table presents long-lived assets by geographic location (in thousands): December 31, 2015 2014 Long-lived Assets: Domestic $ 52,228 $ 43,659 Foreign 968 652 $ 53,196 $ 44,311

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The recorded values of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate their fair value based on their short-term nature. Long-term debt recorded in the Company’s Consolidated Balance Sheets at December 31, 2015 was $755.5 million (net of $18.5 million of unamortized deferred loan costs, see "Note 6. Long-Term Debt" ). The f air value of the long-term debt at that same date was $779.8 million as determined using the quoted price technique, based on Level 2 inputs (significant observable inputs other than quoted prices for identical assets in active markets) from the fair value hierarchy, and included the yields of comparable companies with similar credit characteristics . Related to its acquisitions, at December 31, 2015 , the Company had obligations to pay contingent consideration in cash if certain performance targets were met. The fair value of this contingent consideration was determined using an expected present value technique. Expected cash flows were determined using the probability-weighted average of possible outcomes that would occur should certain financial metrics be reached. There is no market data available to use in valuing the contingent consideration, therefore, the Company developed its own assumptions related to the future financial performance of the businesses to evaluate the fair value of these liabilities. As such, the contingent consideration is classified within Level 3 inputs (unobservable inputs) from the fair value hierarchy. The fair value of the liability for contingent consideration is established at the time of the acquisition and finalized by the end of the measurement period. Its fair value i s then remeasured on a recurring basis with c hanges due to the accretion of the present value discount, recorded in interest expense and changes related to new developments in expected performance, recorded in SG&A. In 2015 there was discount accretion totaling $1.4 million and expense of $2.8 million related to an increase in the obligation. The performance period for these contingent consideration arrangements ended on December 31, 2015; the liability was estimated to be $21.0 million and is included in other current liabilities. At December 31, 2014, contingent consideration was estimated to be $3.0 million a nd was included in other long-term liabilities (refer to "Note 4. Acquisitions" for further information). The reconciliation of contingent consideration liability measured and carried at fair value on a recurring basis with the use of significant unobservable inputs (Level 3) are as follows (in thousands): Year Ended December 31, 2015 2014 Balance at beginning of year $ (3,000 ) $ (3,667 ) Additions for acquisitions (13,814 ) — Payments on contingent consideration — 691 Fair value adjustments (4,167 ) — Foreign currency translation adjustment — (24 ) Balance at end of year $ (20,981 ) $ (3,000 ) Certain assets and liabilities, such as goodwill, are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances (e.g., when there is evidence of impairment). For 2015 and 2014 , no fair value adjustments were required for non-financial assets or liabilities.

Unaudited Quarterly Financial R

Unaudited Quarterly Financial Results	12 Months Ended
Unaudited Quarterly Financial Results	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Result	Unaudited Quarterly Results The following tables present unaudited quarterly financial information. In the opinion of the Company’s management, the quarterly information contains all adjustments, consisting only of normal recurring accruals, necessary for a fair presentation thereof. The operating results for any quarter are not necessarily indicative of the results for any future periods. The Company's Physician Segment and European retained search unit are reported as discontinued operations for all periods presented, see "Note 5. Discontinued Operations" for further information regarding the divestitures. Quarter Ended Year Ended Dec. 31, 2015 Mar. 31, June 30, Sept. 30, Dec. 31, (in thousands, except per share amounts) Revenues $ 430,045 $ 485,323 $ 572,123 $ 577,517 $ 2,065,008 Gross profit 135,875 158,534 191,404 192,932 678,745 Income from continuing operations 13,023 14,335 24,891 19,173 71,422 Income from discontinued operations, net of income taxes 26,112 (83 ) 34 165 26,228 Net income $ 39,135 $ 14,252 $ 24,925 $ 19,338 $ 97,650 Basic earnings per common share: Continuing operations $ 0.25 $ 0.28 $ 0.47 $ 0.36 $ 1.37 Discontinued operations 0.51 (0.01 ) — 0.01 0.50 Net income $ 0.76 $ 0.27 $ 0.47 $ 0.37 $ 1.87 Diluted earnings per common share: Continuing operations $ 0.25 $ 0.27 $ 0.47 $ 0.36 $ 1.35 Discontinued operations 0.50 — — — 0.49 Net income $ 0.75 $ 0.27 $ 0.47 $ 0.36 $ 1.84 Quarter Ended Year Ended Dec. 31, 2014 Mar. 31, June 30, Sept. 30, Dec. 31, (in thousands, except per share amounts) Revenues $ 406,851 $ 434,424 $ 442,443 $ 441,023 $ 1,724,741 Gross profit 128,155 141,905 144,838 142,537 557,435 Income from continuing operations 13,605 19,641 20,723 19,526 73,495 Income from discontinued operations, net of income taxes 312 1,148 1,282 947 3,689 Net income $ 13,917 $ 20,789 $ 22,005 $ 20,473 $ 77,184 Basic earnings per common share: Continuing operations $ 0.25 $ 0.36 $ 0.39 $ 0.38 $ 1.38 Discontinued operations 0.01 0.02 0.02 0.01 0.06 Net income $ 0.26 $ 0.38 $ 0.41 $ 0.39 $ 1.44 Diluted earnings per common share: Continuing operations $ 0.25 $ 0.36 $ 0.38 $ 0.37 $ 1.35 Discontinued operations — 0.02 0.03 0.02 0.07 Net income $ 0.25 $ 0.38 $ 0.41 $ 0.39 $ 1.42

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
Schedule II - Valuation and Qualifying Accounts	Dec. 31, 2013
Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	Description Balance at beginning of year Provisions Deductions from reserves Balance at end of year Year ended December 31, 2015 Allowance for doubtful accounts and billing adjustments $ 4,404 10,486 (8,208 ) $ 6,682 Workers’ compensation loss reserves $ 15,564 2,117 (2,661 ) $ 15,020 Year ended December 31, 2014 Allowance for doubtful accounts and billing adjustments $ 2,465 6,680 (4,741 ) $ 4,404 Workers’ compensation loss reserves $ 17,123 2,211 (3,770 ) $ 15,564 Year ended December 31, 2013 Allowance for doubtful accounts and billing adjustments $ 3,395 1,474 (2,404 ) $ 2,465 Workers’ compensation loss reserves $ 17,037 5,850 (5,764 ) $ 17,123

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition. Revenues from contract assignments, net of sales adjustments and discounts, are recognized when earned, based on hours worked by the Company’s contract professionals on a weekly basis. Permanent placement revenues are derived from direct hire and conversion fees. Direct hire fees relate to employment candidates that the Company directly places as permanent employees at a client organization. Conversion fees relate to contract professionals on assignment that convert to be permanent employees of the client. Direct hire and conversion fees are recognized as revenues when employment candidates or contract professionals begin permanent employment. The Company records a sales allowance against consolidated revenues, which is an estimate based on historical billing adjustment experience. The billing adjustment reserve includes an allowance for fallouts. Fallouts are permanent placements that do not complete the contingency period, which is typically 90 days or less. The Company includes reimbursed expenses, in revenues and the associated amounts of reimbursable expenses in costs of services. The Company records revenues on a gross basis as a principal or on a net basis as an agent depending on the arrangement. The key indicators as to whether it acts as a principal or an agent are whether the Company (i) has the direct contractual relationships with its customers, (ii) bears the risks and rewards of the transactions and (iii) has the discretion to select the contract professionals and establish their price.
Cost of Sales, Policy [Policy Text Block]	Costs of Services. Costs of services include direct costs of contract assignments consisting primarily of payroll, payroll taxes and benefit costs for the Company’s contract professionals. Costs of services also include assignment expenses, many of which are reimbursable by the client.
Income Tax	Income Taxes. Income taxes are accounted for using the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that a portion of the deferred tax asset will not be realized. The Company makes a comprehensive review of its uncertain tax positions regularly. An uncertain tax position represents the Company’s expected treatment of a tax position taken in a filed return, or planned to be taken in a future tax return or claim that has not been reflected in measuring income tax expense for financial reporting purposes. In general, until these positions are sustained by the taxing authorities or statutes expire for the year that the position was taken, the Company does not recognize the tax benefits resulting from such positions and reports the tax effects as a liability for uncertain tax positions.
Foreign Currency Transactions	Foreign Currency Translation. The functional currency of the Company’s foreign operations is their local currency, and as such, their assets and liabilities are translated into U.S. dollars at the rate of exchange in effect on the balance sheet date. Revenues and expenses are translated at the average rates of exchange prevailing during each monthly period. The related translation adjustments are recorded as cumulative foreign currency translation adjustments in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. Gains and losses resulting from foreign currency transactions, which are not material, are included in SG&A expenses in the Consolidated Statements of Operations and Comprehensive Income.
Cash and Cash Equivalents	Cash and Cash Equivalents. The Company considers all highly liquid investments with a maturity of three months or less on the date of purchase to be cash equivalents.
Allowance for Doubtful Accounts and Billing Adjustments	Allowance for Doubtful Accounts and Billing Adjustments. The Company estimates an allowance for doubtful accounts and an allowance for billing adjustments related to trade receivables based on an analysis of historical collection and billing adjustment experience. The Company applies bad debt percentages based on experience to the outstanding accounts receivable balances at the end of the period. The Company also analyzes specific reserves as needed. The allowance for billing adjustments includes a reserve for fallouts which is also based on historical experience. Receivables are written-off when deemed uncollectible.
Property and Equipment	Property and Equipment. Property and equipment are stated at cost. Depreciation and amortization are provided using the straight-line method over the estimated useful lives of the related assets, generally three to five years. Leasehold improvements are amortized over the shorter of the life of the related asset or the remaining term of the lease. Costs associated with customized internal-use software systems that have reached the application development stage and meet recoverability tests are capitalized. Such capitalized costs include external direct costs utilized in developing or obtaining the applications and payroll and payroll-related expenses for employees who are directly associated with the application development.
Business Combinations	Business Combinations. The purchase price of an acquisition is allocated to the underlying assets acquired and liabilities assumed based upon their estimated fair values at the date of acquisition. To the extent the purchase price exceeds the fair value of the net identifiable tangible and intangible assets acquired and liabilities assumed, such excess is allocated to goodwill. The Company determines the estimated fair values after review and consideration of relevant information including discounted cash flows, quoted market prices and estimates made by management. Accordingly, these can be affected by contract performance and other factors over time, which may cause final amounts to differ materially from original estimates. The Company adjusts the preliminary purchase price allocation, as necessary, up to one year after the acquisition closing date if it obtains more information regarding asset valuations and liabilities assumed. Goodwill acquired in business combinations is assigned to the reporting unit(s) expected to benefit from the combination as of the acquisition date. Acquisition-related costs are recognized separately from the acquisition and are expensed as incurred.
Goodwill and Identifiable Intangible Assets	Goodwill and Identifiable Intangible Assets. Goodwill and indefinite-lived intangible assets (consisting entirely of trademarks) are tested for impairment on an annual basis as of October 31. Interim testing of goodwill and indefinite-lived intangible assets for impairment is also required whenever an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit or asset below its carrying amount. In order to test the trademarks for impairment, the Company estimates the fair value of the trademarks and compares such amount to their carrying value. The Company estimates the fair value of the trademarks using a projected discounted cash flow analysis, specifically a relief-from-royalty approach. The principal factors used in the discounted cash flow analysis requiring judgment are projected net sales, discount rate, royalty rate and terminal growth assumption. The royalty rates used in the analysis are based on royalty agreements and franchise agreements that have occurred in the staffing and services industries. Based upon the annual trademark impairment tests completed in 2015 , 2014 and 2013 , there were no indications of impairment of the trademarks, and no impairment charges. Intangible assets having finite lives are amortized over their useful lives and are tested for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Customer relationships are amortized using an accelerated method based on the annual cash flow observed in the initial valuation of the asset. Contractor relationships and non-compete agreements are amortized using the straight-line method. Goodwill is tested for impairment using a two-step process. The first step (Step 1) compares the fair value of a reporting unit to the reporting unit's carrying value. A reporting unit is generally an operating segment or one level below the operating segment level where a business operates and for which discrete financial information is available and reviewed by segment management. If after performing Step 1 of the goodwill impairment test, the fair value of equity of any reporting unit does not exceed its carrying value, the Company performs a second step (Step 2) of the goodwill impairment test for that reporting unit. Step 2 measures the amount of goodwill impairment by comparing the implied fair value of the respective reporting unit goodwill with the carrying value of that goodwill. The reporting unit goodwill impairment loss, if any, is measured as the amount by which the carrying value of goodwill exceeds the implied fair value of goodwill calculated in Step 2 of the goodwill impairment test.
Impairment or Disposal of Long-Lived Assets	Impairment or Disposal of Long-Lived Assets. The Company evaluates long-lived assets, other than goodwill and identifiable intangible assets with indefinite lives, for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. An impairment loss is recognized when the sum of the undiscounted future cash flows is less than the carrying amount of the asset, in which case a write-down is recorded to reduce the related asset to its estimated fair value. There were no significant impairments of long-lived assets in 2015 , 2014 and 2013 .
workers compensation loss reserve [Policy Text Block]	Workers’ Compensation Loss Reserves. The Company carries retention policies for its workers’ compensation liability exposures. In connection with these programs, the Company pays a base premium plus actual losses incurred, not to exceed certain stop-loss limits. The Company is insured for losses above these limits, both per occurrence and in the aggregate. The workers' compensation loss reserves are based upon an actuarial report obtained from a third party and determined based on claims filed and claims incurred but not reported. The Company accounts for claims incurred but not yet reported based on estimates derived from historical claims experience and current trends of industry data. Changes in estimates and differences in estimates and actual payments for claims are recognized in the period that the estimates changed or the payments were made.
Contingencies	Contingencies. The Company records an estimated loss from a loss contingency when information available prior to issuance of its financial statements indicates it is probable that an asset has been impaired or a liability has been incurred at the date of the financial statements, and the amount of the loss can be reasonably estimated. Accounting for contingencies, such as legal settlements, and workers’ compensation matters, requires the Company to use judgment.
Stock-based Compensation	Stock-Based Compensation. The Company records compensation expense for restricted stock awards and restricted stock units based on the fair market value of the awards on the date of grant. Compensation expense for performance-based awards is measured based on the amount of shares ultimately expected to vest, estimated at each reporting date based on management’s expectations regarding the relevant performance criteria. The Company accounts for stock options granted and employee stock purchase plan shares based on an estimated fair market value using a Black-Scholes option valuation model. This methodology requires the use of subjective assumptions including expected stock price volatility and the estimated life of each award. The fair value of equity-based compensation awards less the estimated forfeitures is amortized over the vesting period of the award.
Concentration of Credit Risk	Concentration of Credit Risk. Financial instruments that potentially subject the Company to credit risks consist primarily of cash, cash equivalents and trade receivables. The Company places its cash and cash equivalents in low risk investments with quality credit institutions and limits the amount of credit exposure with any single institution above FDIC insured limits. Concentration of credit risk with respect to accounts receivable is limited because of the large number of geographically dispersed customers, thus spreading the trade credit risk. The Company performs ongoing credit evaluations to identify risks and maintains an allowance to address these risks.
Advertising Costs	Advertising Costs. Advertising costs, which are expensed as incurred, were $3.6 million in 2015 , $4.8 million in 2014 , and $4.0 million in 2013 , and are included in SG&A expenses.

Acquisitions Business Combinati

Acquisitions Business Combinations (Policies)	12 Months Ended
Acquisitions Business Combinations (Policies)	Dec. 31, 2015
Business Combinations [Abstract]
Acquisition [Policy Text Block]	Assets and liabilities of the acquired companies were recorded at their estimated fair values at the dates of acquisition. The excess purchase price over the fair value of net tangible assets and identifiable intangible assets acquired has been allocated to goodwill. The fair value assigned to identifiable intangible assets was determined primarily by using a discounted cash flow method.

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value of Financial Instruments Policy (Policies)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments, Policy [Policy Text Block]	The recorded values of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate their fair value based on their short-term nature. Long-term debt recorded in the Company’s Consolidated Balance Sheets at December 31, 2015 was $755.5 million (net of $18.5 million of unamortized deferred loan costs, see "Note 6. Long-Term Debt" ). The f air value of the long-term debt at that same date was $779.8 million as determined using the quoted price technique, based on Level 2 inputs (significant observable inputs other than quoted prices for identical assets in active markets) from the fair value hierarchy, and included the yields of comparable companies with similar credit characteristics . Related to its acquisitions, at December 31, 2015 , the Company had obligations to pay contingent consideration in cash if certain performance targets were met. The fair value of this contingent consideration was determined using an expected present value technique. Expected cash flows were determined using the probability-weighted average of possible outcomes that would occur should certain financial metrics be reached. There is no market data available to use in valuing the contingent consideration, therefore, the Company developed its own assumptions related to the future financial performance of the businesses to evaluate the fair value of these liabilities. As such, the contingent consideration is classified within Level 3 inputs (unobservable inputs) from the fair value hierarchy. The fair value of the liability for contingent consideration is established at the time of the acquisition and finalized by the end of the measurement period. Its fair value i s then remeasured on a recurring basis with c hanges due to the accretion of the present value discount, recorded in interest expense and changes related to new developments in expected performance, recorded in SG&A. In 2015 there was discount accretion totaling $1.4 million and expense of $2.8 million related to an increase in the obligation. The performance period for these contingent consideration arrangements ended on December 31, 2015; the liability was estimated to be $21.0 million and is included in other current liabilities. At December 31, 2014, contingent consideration was estimated to be $3.0 million a nd was included in other long-term liabilities

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
Property and Equipment (Tables)	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment at December 31, 2015 and 2014 consisted of the following (in thousands): 2015 2014 Furniture, fixtures and equipment $ 14,445 $ 10,957 Computers and related equipment 33,121 21,741 Computer software 52,929 41,416 Leasehold improvements 10,551 5,637 Work-in-progress 4,139 11,943 115,185 91,694 Less -- accumulated depreciation (61,989 ) (47,383 ) $ 53,196 $ 44,311

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
Acquisitions (Tables)	Dec. 31, 2015
Business Combinations [Abstract]
Schedule of Purchase Price Allocation	The Company's allocation of the purchase price of Creative Circle, LabResource and CyberCoders has been finalized and the following table summarizes the allocations (in thousands): 2015 Acquisitions 2013 Acquisition Creative Circle LabResource CyberCoders Cash $ 4,840 $ 187 $ 1,192 Accounts receivable 34,386 1,643 4,298 Prepaid expenses and other current assets 4,462 — 5,839 Property and equipment 5,077 12 3,327 Goodwill 358,029 6,449 69,018 Identifiable intangible assets 194,500 7,528 37,860 Other 651 — 915 Total assets acquired $ 601,945 $ 15,819 $ 122,449 Current liabilities $ 12,254 $ 1,482 $ 9,022 Other — 1,882 16,839 Total liabilities assumed 12,254 3,364 25,861 Total purchase price (1) (2) $ 589,691 $ 12,455 $ 96,588
Schedule of Intangible Assets Acquired as Part of Business Combinations	The following table summarizes (in thousands) the allocation of the purchase price among the identifiable intangible assets for the acquisitions: Identifiable Intangible Asset Value 2015 Acquisitions 2013 Acquisition Useful life Creative Circle LabResource CyberCoders Contractor relationships 2 - 4 years $ 29,500 $ 947 $ 4,000 Customer relationships 2 - 10 years 90,700 5,421 860 Non-compete agreements 2 - 6 years 7,300 20 800 Favorable contracts 5 years 900 — — In-use software 6 years — — 18,900 Trademarks indefinite 66,100 1,140 13,300 Total identifiable intangible assets acquired $ 194,500 $ 7,528 $ 37,860
Schedule of Pro Forma Consolidated Results of Operations	The pro forma financial information is not necessarily indicative of the operating results that would have occurred if the acquisitions had been consummated as of the date indicated, nor are they necessarily indicative of future operating results. Year Ended December 31, 2015 2014 2013 Revenues $ 2,178,954 $ 1,960,851 $ 1,582,699 Income from continuing operations $ 79,159 $ 65,152 $ 54,947 Net income $ 105,387 $ 68,841 $ 88,319 Basic earnings per share: Income from continuing operations $ 1.50 $ 1.20 $ 1.03 Net income $ 2.00 $ 1.27 $ 1.65 Diluted earnings per share: Income from continuing operations $ 1.48 $ 1.18 $ 1.01 Net income $ 1.97 $ 1.25 $ 1.62 Number of shares and share equivalents used to calculate earnings per share: Basic 52,632 54,232 53,481 Diluted 53,411 55,124 54,555

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
Discontinued Operations (Tables)	Dec. 31, 2015
Discontinued Operations [Abstract]
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	The following table is a reconciliation of the major classes of assets and liabilities of the Physician Segment that are presented separately in the consolidated balance sheet at December 31, 2014 (in thousands): December 31, 2014 As Previously Reported (1) Physician Segment As Adjusted Cash and cash equivalents $ 31,714 $ (2,854 ) $ 28,860 Accounts receivable, net 298,761 (21,615 ) 277,146 Prepaid expenses and income taxes 14,513 (1,205 ) 13,308 Workers' compensation and medical malpractice receivable 18,728 (5,358 ) 13,370 Other current assets 2,310 — 2,310 Current assets of discontinued operations — 31,032 31,032 Total current assets 366,026 — 366,026 Property and equipment, net 46,819 (2,508 ) 44,311 Goodwill 570,697 (58,637 ) 512,060 Identifiable intangible assets, net 262,569 (11,960 ) 250,609 Other non-current assets 5,728 (568 ) 5,160 Non-current assets of discontinued operations — 73,673 73,673 Total assets $ 1,251,839 $ — $ 1,251,839 Current portion of long-term debt $ 17,439 $ — $ 17,439 Accounts payable 8,876 (951 ) 7,925 Accrued payroll and contract professional pay 87,189 (4,626 ) 82,563 Workers’ compensation and medical malpractice loss reserves 29,135 (13,571 ) 15,564 Income taxes payable 340 — 340 Other current liabilities 21,776 (1,047 ) 20,729 Current liabilities of discontinued operations — 20,195 20,195 Total current liabilities 164,755 — 164,755 Long-term debt 394,418 — 394,418 Deferred income tax liabilities 48,842 (767 ) 48,075 Other long-term liabilities 9,416 (1,479 ) 7,937 Long-term liabilities of discontinued operations — 2,246 2,246 Total liabilities $ 617,431 $ — $ 617,431 The cash flows that are attributable to the Physician Segment are as follows (in thousands): Year Ended December 31, 2015 2014 2013 Net cash provided by (used in) operating activities $ (1,778 ) $ 836 $ (108 ) Net cash provided by (used in) investing activities: Cash received from sale of discontinued operations, net $ 115,440 $ — $ — Other (14 ) (308 ) (183 ) Total cash provided by (used in) investing activities $ 115,426 $ (308 ) $ (183 ) The following is a summary of the operating results of all of the Company's discontinued operations (in thousands): Year Ended December 31, 2015 2014 2013 Revenues $ 12,068 $ 137,166 $ 153,465 Costs of services 8,653 94,848 106,728 Gross profit 3,415 42,318 46,737 Selling, general and administrative expenses 2,385 33,078 38,991 Amortization of intangible assets 155 2,721 808 Operating income 875 6,519 6,938 Interest expense, net — — (2,456 ) Income before income taxes 875 6,519 4,482 Provision for income taxes 350 2,830 1,950 Income from discontinued operations, net of income taxes $ 525 $ 3,689 $ 2,532

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Long-term Debt	At December 31, 2015 and 2014 , long-term debt consisted of the following (in thousands): 2015 2014 $150 million revolving credit facility, due June 2020 $ 50,000 $ — $825 million Term B loan facility, due June 2022 724,000 — $125 million revolving credit facility, repaid June 2015 — 76,000 Term A loan facility, repaid June 2015 — 158,813 Term B loan facility, repaid June 2015 — 180,312 774,000 415,125 Unamortized deferred loan costs (18,492 ) (3,268 ) $ 755,508 $ 411,857

Goodwill and Identifiable Ass31

Goodwill and Identifiable Assets (Tables)	12 Months Ended
Goodwill and Identifiable Assets (Tables)	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amount of goodwill for the years ended December 31, 2015 and 2014 are as follows (in thousands): Apex Oxford Total Balance as of December 31, 2013 $ 289,712 $ 224,714 $ 514,426 Translation adjustment (1,761 ) (605 ) (2,366 ) Balance as of December 31, 2014 287,951 224,109 512,060 Creative Circle Acquisition 358,029 — 358,029 LabResource Acquisition — 6,449 6,449 Translation adjustment (1,363 ) (269 ) (1,632 ) Balance as of December 31, 2015 $ 644,617 $ 230,289 $ 874,906
Schedule of Acquired Intangible Assets	As of December 31, 2015 and 2014 , the Company had the following acquired intangible assets (in thousands): 2015 2014 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Subject to amortization: Customer relationships 2 - 10 years $ 196,472 $ 74,640 $ 121,832 $ 101,141 $ 53,434 $ 47,707 Contractor relationships 2 - 5 years 69,764 40,124 29,640 39,332 32,021 7,311 Non-compete agreements 2 - 7 years 10,874 3,163 7,711 3,654 1,922 1,732 Favorable contracts 5 years 900 172 728 — — — In-use software 6 years 18,900 6,516 12,384 18,900 3,366 15,534 296,910 124,615 172,295 163,027 90,743 72,284 Not subject to amortization: Trademarks 245,630 — 245,630 178,325 — 178,325 Total $ 542,540 $ 124,615 $ 417,925 $ 341,352 $ 90,743 $ 250,609
Schedule of Estimated Future Amortization Expense	Estimated amortization for each of the next five years and thereafter are as follows (in thousands): 2016 $ 39,657 2017 33,029 2018 28,904 2019 22,008 2020 14,496 Thereafter 34,201 $ 172,295

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Contractual Cash Obligation Payments	The following is a summary of specified contractual cash obligation payments by the Company, as of December 31, 2015 (in thousands): Operating Leases Related Party Leases Total 2016 $ 18,369 $ 1,190 $ 19,559 2017 15,533 1,169 16,702 2018 12,994 1,302 14,296 2019 9,989 1,282 11,271 2020 7,573 1,314 8,887 Thereafter 11,854 5,346 17,200 Total $ 76,312 $ 11,603 $ 87,915

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Components of Income Taxes	The provision for income taxes consists of the following (in thousands): Year Ended December 31, 2015 2014 2013 Current: Federal $ 31,295 $ 28,581 $ 26,284 State 5,837 5,060 4,910 Foreign 2,048 2,181 1,204 39,180 35,822 32,398 Deferred: Federal & State 11,520 15,991 4,244 Foreign (209 ) (256 ) (84 ) 11,311 15,735 4,160 $ 50,491 $ 51,557 $ 36,558
Income (Loss) before Income Tax Provision	Income from continuing operations before income taxes consists of the following (in thousands): Year Ended December 31, 2015 2014 2013 United States $ 116,011 $ 122,496 $ 82,970 Foreign 5,902 2,556 4,728 $ 121,913 $ 125,052 $ 87,698
Schedule of Deferred Tax Assets and Liabilities	The components of deferred tax assets (liabilities) are as follows (in thousands): December 31, 2015 2014 Intangibles $ (70,588 ) $ (59,226 ) Depreciation expense (14,369 ) (13,405 ) Allowance for doubtful accounts 2,607 2,027 Employee related accruals 7,573 7,240 Workers’ compensation and medical malpractice loss reserves 720 4,068 Stock-based compensation 7,354 3,022 Other 5,061 7,286 Net operating loss carryforwards 1,147 1,260 Valuation allowance (1,044 ) (1,114 ) $ (61,539 ) $ (48,842 )
Schedule of Effective Income Tax Rate Reconciliation	The reconciliation between the amount computed by applying the U.S. federal statutory tax rate of 35.0 percent to income before income taxes and the income tax provision is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Income tax provision at the statutory rate $ 42,669 $ 43,768 $ 30,694 State income taxes, net of federal benefit 4,559 4,674 3,807 Disallowed meals and entertainment expenses 1,718 1,608 1,592 Other 1,545 1,507 465 $ 50,491 $ 51,557 $ 36,558
Schedule of Unrecognized Tax Benefits Roll Forward	The following is a reconciliation of the total amounts of unrecognized tax benefits (in thousands): Year Ended December 31, 2015 2014 2013 Unrecognized tax benefit beginning of year $ 848 $ 979 $ 376 Gross increases - tax positions in prior year — 126 1,240 Gross decreases - tax positions in prior year (34 ) — (177 ) Lapse of the statute of limitations — (131 ) — Discontinued operations — (126 ) (460 ) Unrecognized tax benefit end of year $ 814 $ 848 $ 979

Earnings per share (Tables)

Earnings per share (Tables)	12 Months Ended
Earnings per share (Tables)	Dec. 31, 2015
Earnings Per Share [Abstract]
Reconciliation of Shares Used to Compute Basic and Diluted Earnings per Share	The following is a reconciliation of the shares used to compute basic and diluted earnings per share (in thousands): Year Ended December 31, 2015 2014 2013 Weighted average number of common shares outstanding used to compute basic earnings per share 52,259 53,437 53,481 Dilutive effect of stock-based awards 746 857 1,074 Number of shares used to compute diluted earnings per share 53,005 54,294 54,555

Accumulated Other Comprehensi35

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
Accumulated Other Comprehensive Income (Tables)	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The components of accumulated other comprehensive income (loss) were as follows (in thousands): Foreign currency translation adjustment Changes in fair value of derivative, net of tax Accumulated other comprehensive income (loss) Balance at December 31, 2012 $ (804 ) $ (401 ) $ (1,205 ) Other comprehensive income 1,128 193 1,321 Balance at December 31, 2013 324 (208 ) 116 Other comprehensive income (4,772 ) 86 (4,686 ) Balance at December 31, 2014 (4,448 ) (122 ) (4,570 ) Other comprehensive income (3,714 ) 122 (3,592 ) Balance at December 31, 2015 $ (8,162 ) $ — $ (8,162 )

Stock-based Compensation_ Inc36

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]	Year Ended December 31, 2015 2014 2013 Continuing operations $ 22,018 $ 15,623 $ 13,533 Discontinued operations — 576 878 Total $ 22,018 $ 16,199 $ 14,411
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]	A summary of the status of the Company’s unvested RSUs as of December 31, 2015 and changes during the year then ended are presented below: Service Conditions Performance and Service Conditions Total Weighted Average Grant-Date Fair Value Per Unit Unvested RSUs outstanding at December 31, 2014 705,373 381,188 1,086,561 $ 24.88 Granted 213,649 712,108 925,757 $ 40.49 Market value share count adjustment for liability awards — 18,619 18,619 $ 35.09 Vested (423,280 ) (204,936 ) (628,216 ) $ 24.76 Forfeited (30,373 ) (25,728 ) (56,101 ) $ 31.38 Unvested RSUs outstanding at December 31, 2015 465,369 881,251 1,346,620 $ 36.31 Unvested and expected to vest RSUs outstanding at December 31, 2015 437,699 826,620 1,264,319 $ 36.05
Schedule of Other Share-based Compensation, Activity [Table Text Block]	The following table summarizes the balance of liability awards and changes during the years presented (in thousands): 2015 2014 2013 Balances of liability awards at beginning of year $ 1,453 $ 2,500 $ 2,000 Granted — 500 1,000 Settled (1,453 ) (1,497 ) (500 ) Canceled — (50 ) — Balance of liability awards end of year $ — $ 1,453 $ 2,500
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]	The following summarizes pricing and term information for options outstanding as of December 31, 2015 : Options Outstanding Options Exercisable Number Outstanding at Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price Number Exercisable at Weighted Average Exercise Price Range of Exercise Prices December 31, 2015 December 31, 2015 $ 4.44 - $ 8.26 73,901 4.0 $ 6.96 73,305 $ 6.95 $ 10.46 - $ 11.75 61,885 4.3 $ 10.88 60,755 $ 10.89 $ 12.90 - $ 12.90 120,000 1.1 $ 12.90 120,000 $ 12.90 $ 13.31 - $ 13.58 25,600 1.4 $ 13.33 25,506 $ 13.32 $ 16.51 - $ 16.51 75,000 6.7 $ 16.51 60,937 $ 16.51 $ 4.44 - $ 16.51 356,386 3.5 $ 12.11 340,503 $ 11.94
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	The following table is a summary of stock option activity during 2015 : Incentive Stock Options Non- Qualified Stock Options Total Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding at December 31, 2014 4,267 690,614 694,881 $ 11.33 3.5 $ 15,189,000 Exercised (4,267 ) (325,235 ) (329,502 ) $ 10.54 Canceled — (8,993 ) (8,993 ) $ 9.81 Outstanding at December 31, 2015 — 356,386 356,386 $ 12.11 3.5 $ 11,705,000 Vested and Expected to Vest at December 31, 2015 — 356,386 356,386 $ 12.11 3.5 $ 11,705,000 Exercisable at December 31, 2015 — 340,503 340,503 $ 11.94 3.3 $ 11,241,000
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	The table below presents the average fair value per share of shares purchased, and the compensation expense under the ESPP (dollars in thousands, except per share amounts): Year Ended December 31, Average fair value per share Shares Expense 2015 $7.77 204,401 $ 1,586 2014 $8.35 207,805 $ 1,756 2013 $7.16 203,200 $ 1,195

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
Business Segments (Tables)	Dec. 31, 2015
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following tables present revenues, gross profit, operating income and amortization by reportable segment (in thousands): Year ended December 31, 2015 Apex Oxford Corporate (1) Total Revenues $ 1,487,042 $ 577,966 $ — $ 2,065,008 Gross Profit 437,507 241,238 — 678,745 Operating income 151,559 70,385 (69,836 ) 152,108 Amortization 28,371 6,096 — 34,467 Year ended December 31, 2014 Apex Oxford Corporate (1) Total Revenues $ 1,190,052 $ 534,689 $ — $ 1,724,741 Gross Profit 335,322 222,113 — 557,435 Operating income 121,334 70,193 (53,745 ) 137,782 Amortization 16,356 5,765 9 22,130 Year ended December 31, 2013 Apex Oxford Corporate (1) Total Revenues $ 1,059,993 $ 463,108 $ — $ 1,523,101 Gross Profit 294,611 160,264 — 454,875 Operating income 98,588 66,118 (48,119 ) 116,587 Amortization 19,524 1,329 90 20,943
Revenue by Type [Table Text Block]	The following table presents revenues by type (in thousands): Year Ended December 31, 2015 2014 2013 Revenues: Assignment $ 1,947,001 $ 1,641,706 $ 1,500,157 Permanent placement 118,007 83,035 22,944 $ 2,065,008 $ 1,724,741 $ 1,523,101
Disclosure on Geographic Areas, Description of Revenue from External Customers	The Company operates internationally, with operations in the United States, Europe and Canada. The following table presents revenues by geographic location (in thousands): Year Ended December 31, 2015 2014 2013 Revenues: Domestic $ 1,972,888 $ 1,643,598 $ 1,446,805 Foreign 92,120 81,143 76,296 $ 2,065,008 $ 1,724,741 $ 1,523,101
Long Lived Assets By Geographic Location Domestic And Foreign	The following table presents long-lived assets by geographic location (in thousands): December 31, 2015 2014 Long-lived Assets: Domestic $ 52,228 $ 43,659 Foreign 968 652 $ 53,196 $ 44,311

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of Reconciliations of Liabilities Measured and Carried at Fair Value on Recurring Basis, with Significant Unobservable Inputs	The reconciliation of contingent consideration liability measured and carried at fair value on a recurring basis with the use of significant unobservable inputs (Level 3) are as follows (in thousands): Year Ended December 31, 2015 2014 Balance at beginning of year $ (3,000 ) $ (3,667 ) Additions for acquisitions (13,814 ) — Payments on contingent consideration — 691 Fair value adjustments (4,167 ) — Foreign currency translation adjustment — (24 ) Balance at end of year $ (20,981 ) $ (3,000 )

Unaudited Quarterly Financial39

Unaudited Quarterly Financial Results (Tables)	12 Months Ended
Unaudited Quarterly Financial Results (Tables)	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Financial Information	Quarter Ended Year Ended Dec. 31, 2015 Mar. 31, June 30, Sept. 30, Dec. 31, (in thousands, except per share amounts) Revenues $ 430,045 $ 485,323 $ 572,123 $ 577,517 $ 2,065,008 Gross profit 135,875 158,534 191,404 192,932 678,745 Income from continuing operations 13,023 14,335 24,891 19,173 71,422 Income from discontinued operations, net of income taxes 26,112 (83 ) 34 165 26,228 Net income $ 39,135 $ 14,252 $ 24,925 $ 19,338 $ 97,650 Basic earnings per common share: Continuing operations $ 0.25 $ 0.28 $ 0.47 $ 0.36 $ 1.37 Discontinued operations 0.51 (0.01 ) — 0.01 0.50 Net income $ 0.76 $ 0.27 $ 0.47 $ 0.37 $ 1.87 Diluted earnings per common share: Continuing operations $ 0.25 $ 0.27 $ 0.47 $ 0.36 $ 1.35 Discontinued operations 0.50 — — — 0.49 Net income $ 0.75 $ 0.27 $ 0.47 $ 0.36 $ 1.84 Quarter Ended Year Ended Dec. 31, 2014 Mar. 31, June 30, Sept. 30, Dec. 31, (in thousands, except per share amounts) Revenues $ 406,851 $ 434,424 $ 442,443 $ 441,023 $ 1,724,741 Gross profit 128,155 141,905 144,838 142,537 557,435 Income from continuing operations 13,605 19,641 20,723 19,526 73,495 Income from discontinued operations, net of income taxes 312 1,148 1,282 947 3,689 Net income $ 13,917 $ 20,789 $ 22,005 $ 20,473 $ 77,184 Basic earnings per common share: Continuing operations $ 0.25 $ 0.36 $ 0.39 $ 0.38 $ 1.38 Discontinued operations 0.01 0.02 0.02 0.01 0.06 Net income $ 0.26 $ 0.38 $ 0.41 $ 0.39 $ 1.44 Diluted earnings per common share: Continuing operations $ 0.25 $ 0.36 $ 0.38 $ 0.37 $ 1.35 Discontinued operations — 0.02 0.03 0.02 0.07 Net income $ 0.25 $ 0.38 $ 0.41 $ 0.39 $ 1.42

Summary of Significant Accoun40

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Advertising costs	$ 3.6	$ 4.8	$ 4

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment	$ 115,185	$ 91,694
Less -- accumulated depreciation	61,989	47,383
Total	53,196	44,311
Furniture, fixtures and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	14,445	10,957
Computer and related equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	33,121	21,741
Computer Software, Intangible Asset [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	52,929	41,416
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	10,551	5,637
Work-in-progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 4,139	$ 11,943

Property and Equipment (Narrati

Property and Equipment (Narratives) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Net book value	$ 53,196	$ 44,311
Depreciation	16,800	12,300	$ 7,200
Software Development
Property, Plant and Equipment [Line Items]
Net book value	15,700	14,000
Software Development Work-in-Progress
Property, Plant and Equipment [Line Items]
Net book value	$ 2,500	$ 9,000

Acquisitions Acquisitions (Acqu

Acquisitions Acquisitions (Acquisition Costs, by Acquisition) (Details) - USD ($)	Jun. 05, 2015	Apr. 14, 2015	Dec. 31, 2013	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2013	Dec. 05, 2013
Business Acquisition [Line Items]
Stock Issued During Period, Value, Acquisitions					$ 30,183,000
Stock Issued During Period, Shares, Acquisitions					794,700
Creative Circle [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Jun. 5, 2015
Business Acquisition, Name of Acquired Entity	Creative Circle.
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	$ 540,000,000
Stock Issued During Period, Value, Acquisitions				$ 30,200,000
Stock Issued During Period, Shares, Acquisitions				794,700,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount	358,029,000
Business Acquisition Contingent Consideration At Fair Value Accrued Earn-Out	$ 13,800,000
Business Combination, Acquisition Related Costs					$ 5,700,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual					167,200,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual					22,900,000
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		$ 12,700,000
Business Combination, Acquisition Related Costs					400,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual					7,700,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual					$ 1,000,000
CyberCoders [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Dec. 5, 2013
Business Acquisition, Name of Acquired Entity			CyberCoders
Business Acquisition, Description of Acquired Entity			a provider of permanent placement services headquartered in Irvine, California.
Business Combination, Reason for Business Combination			The primary reason for the acquisition was to expand the Company's permanent placement services.
Payments to Acquire Businesses, Gross			$ 93,600,000
Business Combination, Consideration Transferred			96,600,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount							$ 10,300,000
Business Acquisition Contingent Consideration At Fair Value Accrued Earn-Out			$ 3,000,000
contingent consideration maximum							$ 11,000,000
Business Combination, Acquisition Related Costs						$ 1,500,000

Acquisitions (Schedule of Purch

Acquisitions (Schedule of Purchase Price Allocation) (Details) - USD ($) $ in Thousands	Jun. 05, 2015	Apr. 15, 2015	Dec. 31, 2013	Apr. 14, 2015	Dec. 05, 2013
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets					$ 915
Creative Circle [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 4,840
Business Combination, Acquired Receivables, Description	34,386
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets	$ 4,462
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	5,077
BusinessCombinationRecognizedGoodwill	358,029
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	194,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	651
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	601,945
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	12,254
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	12,254
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	$ 589,691
LabResource [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents				$ 187
Business Combination, Acquired Receivables, Description		1,643
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets				0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment				12
BusinessCombinationRecognizedGoodwill				6,449
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				7,528
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets				0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets				15,819
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities				1,482
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other				1,882
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities				3,364
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net				$ 12,455
CyberCoders [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents					1,192
Business Combination, Acquired Receivables, Description			4,298
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets					5,839
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment					3,327
BusinessCombinationRecognizedGoodwill					69,018
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill					37,860
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets					122,449
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities					9,022
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other					16,839
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities					25,861
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net					$ 96,588

Acquisitions Acquisitions (Sche

Acquisitions Acquisitions (Schedule of Intangible Assets Acquired as Part of Business Combination) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Jun. 05, 2015	Apr. 14, 2015	Dec. 05, 2013
Contract-Based Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	5 years
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	6 years
Creative Circle [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 194,500,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount		358,029,000
Creative Circle [Member] \| Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		0
Creative Circle [Member] \| Trademarks [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		66,100,000
Creative Circle [Member] \| Contractor Relations [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		29,500,000
Creative Circle [Member] \| Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		90,700,000
Creative Circle [Member] \| Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		7,300,000
Creative Circle [Member] \| Contract-Based Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 900,000
LabResource [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			$ 7,528,000
LabResource [Member] \| Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			0
LabResource [Member] \| Trademarks [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			1,140,000
LabResource [Member] \| Contractor Relations [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			947,000
LabResource [Member] \| Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			5,421,000
LabResource [Member] \| Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			20,000
LabResource [Member] \| Contract-Based Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			$ 0
CyberCoders [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				$ 37,860,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount				10,300,000
CyberCoders [Member] \| Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				18,900,000
CyberCoders [Member] \| Trademarks [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				13,300,000
CyberCoders [Member] \| Contractor Relations [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				4,000,000
CyberCoders [Member] \| Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				860,000
CyberCoders [Member] \| Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				800,000
CyberCoders [Member] \| Contract-Based Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				$ 0
Minimum [Member] \| Contractor Relations [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	2 years
Minimum [Member] \| Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	2 years
Minimum [Member] \| Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	3 years
Maximum [Member] \| Contractor Relations [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	4 years
Maximum [Member] \| Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	10 years
Maximum [Member] \| Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Assets Average Useful Life	6 years

Acquisitions (Business Acquisit

Acquisitions (Business Acquisition, Pro Forma Information) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition, Pro Forma Information [Abstract]
Revenues	$ 2,178,954	$ 1,960,851	$ 1,582,699
Operating income	79,159	65,152	54,947
Net income	$ 105,387	$ 68,841	$ 88,319
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Basic	$ 1.50	$ 1.20	$ 1.03
Basic earnings per share (in dollars per share)	2	1.27	1.65
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Diluted	1.48	1.18	1.01
Diluted earnings per share (in dollars per share)	$ 1.97	$ 1.25	$ 1.62
Weighted average number of shares outstanding	52,632	54,232	53,481
Weighted average number of shares and dilutive shares outstanding	53,411	55,124	54,555

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ in Thousands	Feb. 01, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations, net of income taxes		$ 25,703	$ 0	$ 30,840
Cash and cash equivalents		23,869	31,714	37,350	$ 27,479
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents			(2,854)
Cash		23,869	28,860
Accounts receivable, net of allowance of $6,682 and $4,404, respectively		354,808	277,146
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net			(21,615)
Prepaid expenses and income taxes		12,686	13,308
Disposal Group, Including Discontinued Operation, Prepaid and Other Assets			(1,205)
Workers' Compensation and Medical Malpractice Receivable, Current			13,370
Disposal Group, Including Discontinued Operations, Workers' Compensation and Medical Malpractice Receivable, Current			(5,358)
Other current assets		9,607	2,310
Disposal Group, Including Discontinued Operation, Other Assets, Current			0
Disposal Group, Including Discontinued Operation, Assets, Current		0	31,032
Assets, Current		414,208	366,026
Property and equipment, net		53,196	44,311
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment			(2,508)
Goodwill		874,906	512,060
Disposal Group, Including Discontinued Operation, Goodwill			(58,637)
Identifiable intangible assets, net		417,925	250,609
Disposal Group, Including Discontinued Operation, Intangible Assets			(11,960)
Other non-current assets		7,072	5,160
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent			(568)
Disposal Group, Including Discontinued Operation, Assets, Noncurrent		0	73,673
Assets		1,767,307	1,251,839
Other Long-term Debt, Current			17,439
Accounts payable		9,132	7,925
Disposal Group, Including Discontinued Operation, Accounts Payable			(951)
Accrued payroll and contract professional pay		88,100	82,563
Disposal Group, Including Discontinued Operation, Accrued Liabilities			(4,626)
Workers' compensation and medical malpractice liability, current			15,564
Disposal Group Workers' Compensation and Medical Malpractice Liability, Current			(13,571)
Accrued Income Taxes, Current			340
Other current liabilities		47,425	20,729
Disposal Group, Including Discontinued Operation, Other Liabilities, Current			(1,047)
Disposal Group, Including Discontinued Operation, Liabilities, Current		0	20,195
Liabilities, Current		160,350	164,755
Long-term Debt, Excluding Current Maturities		755,508	394,418
Deferred income tax liabilities		61,539	48,075
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities, Noncurrent			(767)
Other long-term liabilities		5,116	7,937
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent			(1,479)
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent		0	2,246
Liabilities		982,513	617,431
Cash Provided by (Used in) Operating Activities, Discontinued Operations		(1,778)	836	(108)
Proceeds from Divestiture of Businesses, Net of Cash Divested		115,440	0	59,899
Other Cash Provided by (Used in) Investing Activities, Discontinued Operations		(14)	(308)	(183)
Cash Provided by (Used in) Investing Activities, Discontinued Operations		115,426	(308)	(183)
Disposal Group, Including Discontinued Operation, Revenue		12,068	137,166	153,465
Disposal Group Including Discontinued Operations Cost of Services		8,653	94,848	106,728
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)		3,415	42,318	46,737
Disposal Group, Including Discontinued Operation, General and Administrative Expense		2,385	33,078	38,991
Disposal Group Including Discontinued Operations Amortization of Intangible Assets		155	2,721	808
Disposal Group, Including Discontinued Operation, Operating Income (Loss)		875	6,519	6,938
Disposal Group, Including Discontinued Operation, Interest Expense		0	0	(2,456)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		875	6,519	4,482
Discontinued Operation, Tax Effect of Discontinued Operation		350	2,830	1,950
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		525	3,689	2,532
Scenario, Previously Reported [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents			31,714
Accounts receivable, net of allowance of $6,682 and $4,404, respectively			298,761
Prepaid expenses and income taxes			14,513
Workers' Compensation and Medical Malpractice Receivable, Current			18,728
Other current assets			2,310
Disposal Group, Including Discontinued Operation, Assets, Current			0
Assets, Current			366,026
Property and equipment, net			46,819
Goodwill			570,697
Identifiable intangible assets, net			262,569
Other non-current assets			5,728
Disposal Group, Including Discontinued Operation, Assets, Noncurrent			0
Assets			1,251,839
Other Long-term Debt, Current			17,439
Accounts payable			8,876
Accrued payroll and contract professional pay			87,189
Workers' compensation and medical malpractice liability, current			29,135
Accrued Income Taxes, Current			340
Other current liabilities			21,776
Disposal Group, Including Discontinued Operation, Liabilities, Current			0
Liabilities, Current			164,755
Long-term Debt, Excluding Current Maturities			394,418
Deferred income tax liabilities			48,842
Other long-term liabilities			9,416
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent			0
Liabilities			617,431
Physician Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses	$ 123,000
Gain on sale of discontinued operations, net of income taxes	25,700
Discontinued Operation, Tax Effect of Gain (Loss) from Disposal of Discontinued Operation	$ 14,400
Proceeds from Divestiture of Businesses, Net of Cash Divested		$ 115,440	$ 0	0
AlliedHealthcareandNurseTravel [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses				62,400
Gain on sale of discontinued operations, net of income taxes				30,800
Discontinued Operation, Tax Effect of Gain (Loss) from Disposal of Discontinued Operation				$ 19,500

Long-Term Debt (Details)

Long-Term Debt (Details) $ in Thousands	1 Months Ended	12 Months Ended
Long-Term Debt (Details) $ in Thousands	Jun. 15, 2015Rate	Dec. 31, 2015USD ($)	Jun. 05, 2015USD ($)	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Secured Debt		$ 774,000		$ 415,125
Unamortized Debt Issuance Expense		(18,492)		(3,268)
Long-term Debt		$ 755,508		411,857
Weighted average interest rate		3.68%
Contractual Quarterly Payments		$ 2,100
Payments on Debt		$ 101,000
Leverage ratio		3.02
Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio		4.50
Leverage Ratio in Latest Year of Debt Term		3.25
$825 Million Term B Loan Facility and $150 Million Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Face amount of term loan			$ 975,000
$150 Million Revolving Credit Facility, Due June 2020 [Member]
Debt Instrument [Line Items]
Secured Debt		$ 50,000		0
Face amount of term loan			150,000
$825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Secured Debt		724,000		0
Face amount of term loan			$ 825,000
$125 million revolving credit facility, repaid June 2015 [Member]
Debt Instrument [Line Items]
Secured Debt		0		76,000
Term-A Loan Facility repaid June 2015 [Member]
Debt Instrument [Line Items]
Secured Debt		0		158,813
Term-B Loan Facility repaid June 2015 [Member]
Debt Instrument [Line Items]
Secured Debt		0		$ 180,312
Term Loan Facility \| $150 Million Revolving Credit Facility, Due June 2020 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate borrowings \| Rate	2.50%
Revolving credit facility, unused portion, commitment fee percentage \| Rate	0.00%
Term Loan Facility \| $150 Million Revolving Credit Facility, Due June 2020 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate borrowings \| Rate	0.75%
Revolving credit facility, unused portion, commitment fee percentage \| Rate	0.00%
Term Loan Facility \| $825 Million Term B Loan Facility, due June 2022 [Member] \| Eurodollar [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate borrowings \| Rate	3.00%
Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		$ 96,500

Goodwill and Identifiable Ass49

Goodwill and Identifiable Assets (Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2013
Goodwill [Roll Forward]
Gross goodwill, period start	$ 512,060
Translation adjustment	(1,632)	$ (2,366)
Gross goodwill, period end	(874,906)	514,426
Creative Circle [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	358,029
LabResource [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	6,449
Apex
Goodwill [Roll Forward]
Gross goodwill, period start	287,951
Translation adjustment	(1,363)	(1,761)
Gross goodwill, period end	(644,617)	289,712
Apex \| Creative Circle [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	358,029
Apex \| LabResource [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	0
Oxford
Goodwill [Roll Forward]
Gross goodwill, period start	224,109
Translation adjustment	(269)	(605)
Gross goodwill, period end	(230,289)	$ 224,714
Oxford \| Creative Circle [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	0
Oxford \| LabResource [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	$ 6,449

Goodwill and Identifiable Ass50

Goodwill and Identifiable Assets (Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Intangible assets subject to amortization:
Gross Carrying Amount	$ 296,910	$ 163,027
Accumulated Amortization	124,615	90,743
Net Carrying Amount	172,295	72,284
Intangible assets not subject to amortization:
Trademarks, Carrying Amount	245,630	178,325
Goodwill	874,906	512,060
Total
Gross Carrying Amount	542,540	341,352
Net Carrying Amount	417,925	250,609
Customer Relationships [Member]
Intangible assets subject to amortization:
Gross Carrying Amount	196,472	101,141
Accumulated Amortization	74,640	53,434
Net Carrying Amount	$ 121,832	47,707
Customer Relationships [Member] \| Minimum [Member]
Intangible Assets [Line Items]
Estimated Useful Life	2 months
Customer Relationships [Member] \| Maximum [Member]
Intangible Assets [Line Items]
Estimated Useful Life	10 years
Contractor Relations [Member]
Intangible assets subject to amortization:
Gross Carrying Amount	$ 69,764	39,332
Accumulated Amortization	40,124	32,021
Net Carrying Amount	$ 29,640	7,311
Contractor Relations [Member] \| Minimum [Member]
Intangible Assets [Line Items]
Estimated Useful Life	2 years
Contractor Relations [Member] \| Maximum [Member]
Intangible Assets [Line Items]
Estimated Useful Life	5 years
Noncompete Agreements [Member]
Intangible assets subject to amortization:
Gross Carrying Amount	$ 10,874	3,654
Accumulated Amortization	3,163	1,922
Net Carrying Amount	$ 7,711	1,732
Noncompete Agreements [Member] \| Minimum [Member]
Intangible Assets [Line Items]
Estimated Useful Life	2 years
Noncompete Agreements [Member] \| Maximum [Member]
Intangible Assets [Line Items]
Estimated Useful Life	7 years
Contract-Based Intangible Assets [Member]
Intangible Assets [Line Items]
Estimated Useful Life	5 years
Intangible assets subject to amortization:
Gross Carrying Amount	$ 900
Accumulated Amortization	172
Net Carrying Amount	$ 728
Computer Software, Intangible Asset [Member]
Intangible Assets [Line Items]
Estimated Useful Life	6 years
Intangible assets subject to amortization:
Gross Carrying Amount	$ 18,900	18,900
Accumulated Amortization	6,516	3,366
Net Carrying Amount	$ 12,384	$ 15,534

Goodwill and Identifiable Ass51

Goodwill and Identifiable Assets (Future Amortization Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 34,467	$ 22,130	$ 20,943
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,016	39,657
2,017	33,029
2,018	28,904
2,019	22,008
2,020	14,496
Thereafter	34,201
Net Carrying Amount	$ 172,295	$ 72,284

Commitments and Contingencies52

Commitments and Contingencies (Details) $ in Thousands	12 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Dec. 31, 2015USD ($)property	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Commitment and contingencies [Line Items]
Deferred Rent Credit, Current	$ 500	$ 300
Operating Leases
2,016	18,369
2,017	15,533
2,018	12,994
2,019	9,989
2,020	7,573
Thereafter	11,854
Total	76,312
Related Party
2,016	1,190
2,017	1,169
2,018	1,302
2,019	1,282
2,020	1,314
Thereafter	5,346
Total	11,603
Total
2,016	19,559
2,017	16,702
2,018	14,296
2,019	11,271
2,020	8,887
Thereafter	17,200
Total	87,915
Deferred rent liability, noncurrent	4,300	4,000
Rent expense	21,600	17,600	$ 15,400
Costs and Expenses, Related Party	1,300	1,300	$ 1,300
Self Insurance Reserve	1,800	2,200
Workerscompensationreceivable	13,238	13,370
Letters of credit outstanding	$ 3,500	$ 3,200
Apex Systems
Total
Number of leased properties owned by related parties (in number of properties) \| property	2

Commitments and Contingencies L

Commitments and Contingencies Legal Proceedings (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Workerscompensationreceivable	$ 13,238	$ 13,370
Other Liabilities, Current	$ 47,425	$ 20,729

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Income Tax Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Liability for Uncertain Tax Positions, Noncurrent	$ 900	$ 900	$ 900
Deferred Rent Credit, Current	500	300
Costs and Expenses, Related Party	$ 1,300	$ 1,300	$ 1,300

(Narratives)(Details)

(Narratives)(Details) - USD ($) $ in Thousands	12 Months Ended
(Narratives)(Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 1,000	$ 1,000
Accumulated net earning	249,567	154,562
Gross deferred tax assets	29,200	24,100
Gross deferred tax liabilities	89,700	$ 71,400
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	800		$ 900
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	0
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	8,800
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	4,900
Accumulated net earning	$ 11,000

Income Taxes (Income Tax Compon

Income Taxes (Income Tax Components) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 31,295	$ 28,581	$ 26,284
State	5,837	5,060	4,910
Foreign	2,048	2,181	1,204
Total Current	39,180	35,822	32,398
Deferred:
Federal	11,520	15,991	4,244
Foreign	(209)	(256)	(84)
Total Deferred	11,311	15,735	4,160
Total	$ 50,491	$ 51,557	$ 36,558

Income Taxes (Income Before Tax

Income Taxes (Income Before Tax) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
United States	$ 116,011	$ 122,496	$ 82,970
Foreign	5,902	2,556	4,728
Income before income taxes	$ 121,913	$ 125,052	$ 87,698

Income Taxes (Deferred Tax Asse

Income Taxes (Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Disposal Group, Including Discontinued Operation, Deferred Tax Asset, Current	$ 800
Intangibles	(70,588)	$ (59,226)
Depreciation expense	(14,369)	(13,405)
Allowance for doubtful accounts	2,607	2,027
Employee related accruals	7,573	7,240
Workers’ compensation and medical malpractice loss reserves	720	4,068
Stock-based compensation	7,354	3,022
Other	5,061	7,286
Net operating loss carryforwards	1,147	1,260
Valuation allowance	(1,044)	(1,114)
Total deferred income tax assets (liabilities)	$ (61,539)	$ (48,842)

Income Taxes (Tax Rate Reconcil

Income Taxes (Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax provision at the statutory rate	$ 42,669	$ 43,768	$ 30,694
State income taxes, net of federal benefit	4,559	4,674	3,807
Permanent difference – non deductible items	1,718	1,608	1,592
Other	1,545	1,507	465
Total	$ 50,491	$ 51,557	$ 36,558

Income Taxes (Unrecognized Tax

Income Taxes (Unrecognized Tax Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefit beginning of year	$ 848	$ 979	$ 376
Gross increases - tax positions in prior year	0	126	1,240
Gross Decreases - tax positions in prior year	(34)	0	(177)
Reductions for tax positions as a result of a lapse of the applicable statute of limitations	0	(131)	0
Unrecognized Tax Benefits, Reduction Resulting from Discontinued Operations	0	(126)	(460)
Unrecognized Tax Benefit end of year	$ 814	$ 848	$ 979

Earnings per share (Details)

Earnings per share (Details) - shares shares in Thousands	12 Months Ended
Earnings per share (Details) - shares shares in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Weighted Average Number of Shares Outstanding Reconciliation
Weighted average number of common shares outstanding used to compute basic earnings per share	52,259	53,437	53,481
Dilutive effect of stock-based awards	746	857	1,074
Number of shares used to compute diluted earnings per share	53,005	54,294	54,555

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Jan. 16, 2015	Jul. 21, 2014
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, amount authorized			$ 100,000	$ 100,000
Stock Repurchased and Retired During Period, Shares	43,000	3,400,000
Stock Repurchased and Retired During Period, Value	$ 3,819	$ 100,048
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 98,400
Stock Issued During Period, Shares, Acquisitions	794,700
Stock Repurchased During Period, Value	$ 1,600
Stock Issued During Period, Value, Acquisitions	$ 30,183
sharesreceivedforexercisepriceofoptions	46,174
payment exercise of stock option	$ 2,200
Additional Paid-in Capital [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	(1,173)	(31,194)
Stock Repurchased During Period, Value	400
Stock Issued During Period, Value, Acquisitions	30,175
Retained Earnings [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	(2,645)	$ (68,821)
Stock Repurchased During Period, Value	$ 1,200

Accumulated Other Comprehensi63

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment	$ (8,162)	$ (4,448)	$ 324	$ (804)
Accumulated Other Comprehensive Income (Loss), Derivatives, Net of Tax	0	(122)	(208)	(401)
Changes in fair value of derivative, net of tax	122	86	193
Other Comprehensive Income (Loss), Net of Tax	(3,592)	(4,686)	1,321
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(3,714)	(4,772)	1,128
Accumulated other comprehensive income (loss)	$ (8,162)	$ (4,570)	$ 116	$ (1,205)

Stock-based Compensation_ Inc64

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (RSU and RSAs) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Unvested RSUs and RSAs outstanding at December 31, weighted average grant date fair value (in dollars per share)	$ 36.31
Award with service conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1 (in shares)	705,373
Granted (in shares)	213,649
Market value share count adjustment for liability awards (in shares)	0
Vested (in shares)	(423,280)
Forfeited (in shares)	(30,373)
Unvested RSUs and RSAs outstanding at December 31 (in shares)	465,369	705,373
Unvested and expected to vest RSUs and RSAs outstanding at December 31 (in shares)	437,699
Awards with performance and service conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1 (in shares)	381,188
Granted (in shares)	712,108
Market value share count adjustment for liability awards (in shares)	(18,619)
Vested (in shares)	(204,936)
Forfeited (in shares)	(25,728)
Unvested RSUs and RSAs outstanding at December 31 (in shares)	881,251	381,188
Unvested and expected to vest RSUs and RSAs outstanding at December 31 (in shares)	826,620
Restricted Stock Units and Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1 (in shares)	1,086,561
Granted (in shares)	925,757
Market value share count adjustment for liability awards (in shares)	(18,619)
ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentOtherThanOptionsMarketValueShareCountAdjustmentWeightedAverageGrantDateFairValue	$ 35.09
Vested (in shares)	(628,216)
Forfeited (in shares)	(56,101)
Unvested RSUs and RSAs outstanding at December 31 (in shares)	1,346,620	1,086,561
Unvested and expected to vest RSUs and RSAs outstanding at December 31 (in shares)	1,264,319
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1, weighted average grant date fair value (in dollars per share)	$ 24.88
Granted, weighted average grant date fair value (in dollars per share)	40.49	$ 33.66	$ 26.17
Vested, weighted average grant date fair value (in dollars per share)	24.76
Unvested RSUs and RSAs outstanding at December 31, weighted average grant date fair value (in dollars per share)		$ 24.88
Unvested and expected to vest RSUs and RSAs outstanding at December 31, weighted average grant date fair value (in dollars per share)	$ 36.05
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	31.38

Stock-based Compensation_ Inc65

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 22,018	$ 16,199	$ 14,411
Restricted Stock Units and Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 40.49	$ 33.66	$ 26.17
Shares surrendered by the employees to the Company for payment of minimum tax withholding obligations	229,366
Total intrinsic value of options exercised	$ 24,300	$ 21,300	$ 15,000
Unrecognized compensation expense	$ 30,900
Share-based awards expense, service period	2 years
Liability Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent	$ 0	1,453	2,500	$ 2,000
Liability Awards Granted	0	500	1,000
Liability Awards Settled During Period	(1,453)	(1,497)	(500)
Liability Awards Canceled During Period	0	(50)	0
Allocated Share-based Compensation Expense		500	1,000
Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	22,018	15,623	13,533
Discontinued Operations, Disposed of by Sale [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 0	$ 576	$ 878

Stock-based Compensation_ Inc66

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Range of Prices) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	$ 4.44
Exercise price, high end of the range (in dollars per share)	$ 16.51
Options outstanding (in shares)	356,386	694,881
Options outstanding - weighted average remaining contractual life (years)	3 years 6 months	3 years 6 months
Options outstanding - weighted average exercise price (in dollars per share)	$ 12.11	$ 11.33
Options exercisable - at the end of period (in shares)	340,503
Options exercisable - weighted average exercise price (in dollars per share)	$ 11.94
$4.44 - 8.26
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	4.44
Exercise price, high end of the range (in dollars per share)	$ 8.26
Options outstanding (in shares)	73,901
Options outstanding - weighted average remaining contractual life (years)	4 years
Options outstanding - weighted average exercise price (in dollars per share)	$ 6.96
Options exercisable - at the end of period (in shares)	73,305
Options exercisable - weighted average exercise price (in dollars per share)	$ 6.95
$10.46 - 11.75
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	10.46
Exercise price, high end of the range (in dollars per share)	$ 11.75
Options outstanding (in shares)	61,885
Options outstanding - weighted average remaining contractual life (years)	4 years 3 months 18 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 10.88
Options exercisable - at the end of period (in shares)	60,755
Options exercisable - weighted average exercise price (in dollars per share)	$ 10.89
$12.90 - 12.90
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	12.90
Exercise price, high end of the range (in dollars per share)	$ 12.90
Options outstanding (in shares)	120,000
Options outstanding - weighted average remaining contractual life (years)	1 year 1 month 6 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 12.90
Options exercisable - at the end of period (in shares)	120,000
Options exercisable - weighted average exercise price (in dollars per share)	$ 12.90
$13.31 - 13.58
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	13.31
Exercise price, high end of the range (in dollars per share)	$ 13.58
Options outstanding (in shares)	25,600
Options outstanding - weighted average remaining contractual life (years)	1 year 4 months 24 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 13.33
Options exercisable - at the end of period (in shares)	25,506
Options exercisable - weighted average exercise price (in dollars per share)	$ 13.32
$16.51 - 16.51
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	16.51
Exercise price, high end of the range (in dollars per share)	$ 16.51
Options outstanding (in shares)	75,000
Options outstanding - weighted average remaining contractual life (years)	6 years 8 months 12 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 16.51
Options exercisable - at the end of period (in shares)	60,937
Options exercisable - weighted average exercise price (in dollars per share)	$ 16.51

Stock-based Compensation_ Inc67

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Stock Options Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Outstanding Stock Options Activity [Roll Forward]
Outstanding at January 1 (in shares)	694,881
Exercised (in shares)	(329,502)
Canceled (in shares)	(8,993)
Outstanding at December 31 (in shares)	356,386	694,881
Vested and Expected to Vest at December 31(in shares)	356,386
Exercisable at December 31 (in shares)	340,503
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding - weighted average exercise price per share	$ 11.33
Exercised, weighted average exercise price per share	10.54
Canceled, weighted average exercise price per share	9.81
Vested and Expected to Vest, weighted average exercise price per share	12.11
Exercisable, weighted average exercise price per share	$ 11.94
Outstanding, weighted average remaining contractual term	3 years 6 months	3 years 6 months
Vested and Expected to Vest, weighted average remaining contractual term	3 years 6 months
Exercisable, weighted average remaining contractual term	3 years 3 months 18 days
Options outstanding - aggregate intrinsic value	$ 11,705	$ 15,189
Vested and Expected to Vest, aggregate intrinsic value	11,705
Exercisable, aggregate intrinsic value	11,241
Employee Stock Option [Member]
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Total intrinsic value of options exercised	$ 10,900	$ 3,900	$ 7,600
Incentive Stock Options [Member]
Outstanding Stock Options Activity [Roll Forward]
Outstanding at January 1 (in shares)	4,267
Exercised (in shares)	(4,267)
Canceled (in shares)	0
Outstanding at December 31 (in shares)	0	4,267
Vested and Expected to Vest at December 31(in shares)	0
Exercisable at December 31 (in shares)	0
Non Qualified Stock Options [Member]
Outstanding Stock Options Activity [Roll Forward]
Outstanding at January 1 (in shares)	690,614
Exercised (in shares)	(325,235)
Canceled (in shares)	(8,993)
Outstanding at December 31 (in shares)	356,386	690,614
Vested and Expected to Vest at December 31(in shares)	356,386
Exercisable at December 31 (in shares)	340,503

Stock-based Compensation_ Inc68

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan 401(k) Retirement Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 7.6	$ 7.5	$ 6

Stock-based Compensation_ Inc69

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	15.00%
Allocated Share-based Compensation Expense	$ 22,018	$ 16,199	$ 14,411
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	3,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 7.77	$ 8.35	$ 7.16
Stock Issued During Period, Shares, Employee Stock Purchase Plans	204,401	207,805	203,200
Allocated Share-based Compensation Expense	$ 1,586	$ 1,756	$ 1,195

Stock-based Compensation_ Inc70

Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Recognized Period Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated Share-based Compensation Expense	$ 22,018	$ 16,199	$ 14,411
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	$ 6,551	4,718	5,305
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		4,700	5,100
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,546,962
Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated Share-based Compensation Expense	$ 22,018	15,623	13,533
Discontinued Operations, Disposed of by Sale [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated Share-based Compensation Expense	$ 0	$ 576	$ 878

Business Segments (Segment Repo

Business Segments (Segment Reporting Information) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Mar. 31, 2014USD ($)	Dec. 31, 2015USD ($)property	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Segment Reporting Information
Revenues	$ 577,517	$ 572,123	$ 485,323	$ 430,045	$ 441,023	$ 442,443	$ 434,424	$ 406,851	$ 2,065,008	$ 1,724,741	$ 1,523,101
Gross profit	$ 192,932	$ 191,404	$ 158,534	$ 135,875	$ 142,537	$ 144,838	$ 141,905	$ 128,155	678,745	557,435	454,875
Operating Income									152,108	137,782	116,587
Amortization of intangible assets									$ 34,467	22,130	20,943
Reportable segments (in number of segments) \| property									2
Apex
Segment Reporting Information
Revenues									$ 1,487,042	1,190,052	1,059,993
Gross profit									437,507	335,322	294,611
Operating Income									151,559	121,334	98,588
Amortization of intangible assets									28,371	16,356	19,524
Oxford
Segment Reporting Information
Revenues									577,966	534,689	463,108
Gross profit									241,238	222,113	160,264
Operating Income									70,385	70,193	66,118
Amortization of intangible assets									6,096	5,765	1,329
Corporate
Segment Reporting Information
Operating Income									(69,836)	(53,745)	(48,119)
Amortization of intangible assets									0	9	90
Assignment [Member]
Segment Reporting Information
Revenues									1,947,001	1,641,706	1,500,157
Direct hire and conversion fees [Member]
Segment Reporting Information
Revenues									$ 118,007	$ 83,035	$ 22,944

Business Segments (Revenue by G

Business Segments (Revenue by Geographical Areas) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Total Revenues	$ 577,517	$ 572,123	$ 485,323	$ 430,045	$ 441,023	$ 442,443	$ 434,424	$ 406,851	$ 2,065,008	$ 1,724,741	$ 1,523,101
Domestic [Member]
Revenues:
Total Revenues									1,972,888	1,643,598	1,446,805
Foreign [Member]
Revenues:
Total Revenues									$ 92,120	$ 81,143	$ 76,296

Business Segments (Long-Lived A

Business Segments (Long-Lived Assets) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 577,517	$ 572,123	$ 485,323	$ 430,045	$ 441,023	$ 442,443	$ 434,424	$ 406,851	$ 2,065,008	$ 1,724,741	$ 1,523,101
Long-Lived Assets	53,196				44,311				53,196	44,311
Domestic [Member]
Segment Reporting Information [Line Items]
Revenues									1,972,888	1,643,598	1,446,805
Long-Lived Assets	52,228				43,659				52,228	43,659
Foreign [Member]
Segment Reporting Information [Line Items]
Revenues									92,120	81,143	$ 76,296
Long-Lived Assets	$ 968				$ 652				$ 968	$ 652

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Inputs, Liabilities, Quantitative Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Liabilities, Quantitative Information
Long-term debt	$ 755,508	$ 411,857
Unamortized Debt Issuance Expense	(18,492)	(3,268)
Contingent Consideration Liability [Member]
Fair Value Inputs, Liabilities, Quantitative Information
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	4,167	0
Significant other observable inputs (Level 2)
Fair Value Inputs, Liabilities, Quantitative Information
Long-term debt, fair value	779,800
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Liabilities, Quantitative Information
Obligations, Fair Value Disclosure	21,000	$ 3,000
Interest Expense [Member]
Fair Value Inputs, Liabilities, Quantitative Information
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	1,400
Selling, General and Administrative Expenses [Member]
Fair Value Inputs, Liabilities, Quantitative Information
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	$ 2,800

Fair Value Measurements (Liabil

Fair Value Measurements (Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation) (Details) - Contingent Consideration Liability [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Contingent consideration for acquisitions
Balance at beginning of period	$ (3,000)	$ (3,667)
Additions for acquisitions	(13,814)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Payments	0	691
Fair value adjustment	(4,167)	0
Foreign currency translation adjustment	0	(24)
Balance at end of period	$ (20,981)	$ (3,000)

Unaudited Quarterly Financial76

Unaudited Quarterly Financial Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 577,517	$ 572,123	$ 485,323	$ 430,045	$ 441,023	$ 442,443	$ 434,424	$ 406,851	$ 2,065,008	$ 1,724,741	$ 1,523,101
Gross profit	192,932	191,404	158,534	135,875	142,537	144,838	141,905	128,155	678,745	557,435	454,875
Income from continuing operations	19,173	24,891	14,335	13,023	19,526	20,723	19,641	13,605	71,422	73,495	51,140
Net income	$ 19,338	$ 24,925	$ 14,252	$ 39,135	$ 20,473	$ 22,005	$ 20,789	$ 13,917	$ 97,650	$ 77,184	$ 84,512
Earnings Per Share, Basic [Abstract]
Continuing operations	$ 0.36	$ 0.47	$ 0.28	$ 0.25	$ 0.38	$ 0.39	$ 0.36	$ 0.25	$ 1.37	$ 1.38	$ 0.96
Discontinued operations	0.01	0	(0.01)	0.51	0.01	0.02	0.02	0.01	0.50	0.06	0.62
Net income	0.37	0.47	0.27	0.76	0.39	0.41	0.38	0.26	1.87	1.44	1.58
Earnings Per Share, Diluted [Abstract]
Continuing operations	0.36	0.47	0.27	0.25	0.37	0.38	0.36	0.25	1.35	1.35	0.94
Discontinued operations	0	0	0	0.50	0.02	0.03	0.02	0	0.49	0.07	0.61
Net income	$ 0.36	$ 0.47	$ 0.27	$ 0.75	$ 0.39	$ 0.41	$ 0.38	$ 0.25	$ 1.84	$ 1.42	$ 1.55
Segment Reporting Information
Income from discontinued operations, net of income taxes									$ 525	$ 3,689	$ 2,532
Discontinued Operations, Disposed of by Sale [Member]
Segment Reporting Information
Income from discontinued operations, net of income taxes	$ 165	$ 34	$ (83)	$ 26,112	$ 947	$ 1,282	$ 1,148	$ 312	$ 26,228	$ 3,689

Schedule II - Valuation and Q77

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts and Bilinig Adjustments
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 4,404	$ 2,465	$ 3,395
Provisions	10,486	6,680	1,474
Deductions	(8,208)	(4,741)	(2,404)
Balance at end of year	6,682	4,404	2,465
Allowance for Workers' Compensation and Medical Malpractice Loss Reserves
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	15,564	17,123	17,037
Provisions	2,117	2,211	5,850
Deductions	(2,661)	(3,770)	(5,764)
Balance at end of year	$ 15,020	$ 15,564	$ 17,123