Robert Half International (RHI) 10-K 20 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	RHI
Entity Registrant Name	HALF ROBERT INTERNATIONAL INC /DE/
Entity Central Index Key	315,213
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		124,261,548
Entity Public Float			$ 5,855,668,588

Consolidated Statements of Fina

Consolidated Statements of Financial Position - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 294,753	$ 260,201
Accounts receivable, less allowances of $33,181 and $33,133	732,405	703,228
Other current assets	404,711	320,805
Total current assets	1,431,869	1,284,234
Goodwill	210,885	209,793
Other intangible assets, net	4,946	3,671
Property and equipment, net	144,887	161,509
Noncurrent deferred income taxes	74,867	118,764
Total assets	1,867,454	1,777,971
LIABILITIES
Accounts payable and accrued expenses	126,937	135,540
Accrued payroll and benefit costs	612,899	539,048
Income taxes payable	7,877	5,141
Current portion of notes payable and other indebtedness	183	167
Total current liabilities	747,896	679,896
Notes payable and other indebtedness, less current portion	657	840
Other liabilities	13,636	10,636
Total liabilities	762,189	691,372
Commitments and Contingencies
STOCKHOLDERS’ EQUITY
Preferred stock, $.001 par value authorized 5,000,000 shares; issued and outstanding zero shares	0	0
Common stock, $.001 par value authorized 260,000,000 shares; issued and outstanding 124,261,458 and 127,796,558 shares	124	128
Capital surplus	1,064,601	1,022,411
Accumulated other comprehensive income (loss)	3,507	(20,502)
Retained earnings	37,033	84,562
Total stockholders’ equity	1,105,265	1,086,599
Total liabilities and stockholders’ equity	$ 1,867,454	$ 1,777,971

Consolidated Statements of Fin3

Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 33,181	$ 33,133
Preferred stock, par value (usd per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	5,000,000	5,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	260,000,000	260,000,000
Common stock, issued (in shares)	124,261,458	127,796,558
Common stock, outstanding (in shares)	124,261,458	127,796,558

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net service revenues	$ 5,266,789	$ 5,250,399	$ 5,094,933
Direct costs of services, consisting of payroll, payroll taxes, benefit costs and reimbursable expenses	3,102,977	3,089,723	2,980,462
Gross margin	2,163,812	2,160,676	2,114,471
Selling, general and administrative expenses	1,646,532	1,606,217	1,533,799
Amortization of intangible assets	1,563	1,237	192
Interest income, net	(1,799)	(888)	(550)
Income before income taxes	517,516	554,110	581,030
Provision for income taxes	226,932	210,721	223,234
Net income	$ 290,584	$ 343,389	$ 357,796
Net income per share :
Basic (usd per share)	$ 2.34	$ 2.68	$ 2.72
Diluted (usd per share)	$ 2.33	$ 2.67	$ 2.69
Shares:
Basic (in shares)	124,152	127,991	131,749
Diluted (in shares)	124,892	128,766	132,930
Cash dividends declared per share (usd per share)	$ 0.96	$ 0.88	$ 0.8

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
COMPREHENSIVE INCOME:
Net income	$ 290,584	$ 343,389	$ 357,796
Foreign currency translation adjustments, net of tax	24,009	(10,208)	(25,024)
Total comprehensive income	$ 314,593	$ 333,181	$ 332,772

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	COMMON STOCK	CAPITAL SURPLUS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	RETAINED EARNINGS
Balance at beginning of period, (in shares) at Dec. 31, 2014		135,134
Balance at beginning of period at Dec. 31, 2014		$ 135	$ 928,157	$ 14,730	$ 36,836
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		785
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(4,817)
Repurchases of common stock		$ (5)			(252,916)
Stock-based compensation expense			41,292
Exercises of stock options, (in shares)	54	54
Exercises of stock options		$ 0	1,529
Tax impact of equity incentive plans			8,500
Foreign currency translation adjustments, net of tax	$ (25,024)			(25,024)
Net income	$ 357,796				357,796
Cash dividends					(107,249)
Balance at end of period, (in shares) at Dec. 31, 2015		131,156
Balance at end of period at Dec. 31, 2015		$ 131	979,477	(10,294)	34,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		1,039
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(4,405)
Repurchases of common stock		$ (4)			(178,780)
Stock-based compensation expense			42,699
Exercises of stock options, (in shares)	7	7
Exercises of stock options		$ 0	223
Tax impact of equity incentive plans			13
Foreign currency translation adjustments, net of tax	$ (10,208)			(10,208)
Net income	343,389				343,389
Cash dividends					(114,514)
Balance at end of period, (in shares) at Dec. 31, 2016		127,797
Balance at end of period at Dec. 31, 2016	$ 1,086,599	$ 128	1,022,411	(20,502)	84,562
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		918
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(4,454)
Repurchases of common stock		$ (5)			(217,031)
Stock-based compensation expense			42,191
Exercises of stock options, (in shares)	0	0
Exercises of stock options		$ 0	0
Tax impact of equity incentive plans			0
Foreign currency translation adjustments, net of tax	$ 24,009			24,009
Net income	290,584				290,584
Cash dividends					(121,082)
Balance at end of period, (in shares) at Dec. 31, 2017		124,261
Balance at end of period at Dec. 31, 2017	$ 1,105,265	$ 124	$ 1,064,601	$ 3,507	$ 37,033

Consolidated Statements of Sto7

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
RETAINED EARNINGS
Cash dividends, per share (usd per share)	$ 0.96	$ 0.88	$ 0.80

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 290,584	$ 343,389	$ 357,796
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	1,563	1,237	192
Depreciation expense	63,930	63,078	53,273
Stock-based compensation expense—restricted stock and stock units	42,191	42,699	41,292
Excess tax benefits from stock-based compensation	0	(1,822)	(8,762)
Deferred income taxes	44,091	(1,868)	(8,579)
Provision for doubtful accounts	8,022	9,192	12,005
Changes in assets and liabilities, net of effects of acquisitions:
Increase in accounts receivable	(17,039)	(15,888)	(75,745)
Increase in accounts payable, accrued expenses, accrued payroll and benefit costs	47,832	19,726	60,232
(Decrease) increase in income taxes payable, net	(9,655)	(8,246)	19,948
Change in other assets, net of change in other liabilities	(18,528)	(9,416)	(13,416)
Net cash flows provided by operating activities	452,991	442,081	438,236
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(1,160)	(2,200)	(14,668)
Capital expenditures	(40,753)	(82,956)	(75,057)
Payments to trusts for employee deferred compensation plans	(36,584)	(27,079)	(28,225)
Net cash flows used in investing activities	(78,497)	(112,235)	(117,950)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(231,724)	(176,031)	(271,138)
Cash dividends paid	(121,000)	(114,164)	(107,561)
Decrease in notes payable and other indebtedness	(167)	(154)	(140)
Excess tax benefits from stock-based compensation	0	1,822	8,762
Proceeds from exercises of stock options	0	223	1,529
Net cash flows used in financing activities	(352,891)	(288,304)	(368,548)
Effect of exchange rate changes on cash and cash equivalents	12,949	(5,918)	(14,280)
Net increase (decrease) in cash and cash equivalents	34,552	35,624	(62,542)
Cash and cash equivalents at beginning of period	260,201	224,577	287,119
Cash and cash equivalents at end of period	294,753	260,201	224,577
Cash paid during the year for:
Interest	278	266	285
Income taxes, net of refunds	190,954	219,415	212,668
Non-cash items:
Stock repurchases awaiting settlement	$ 0	$ 14,688	$ 11,935

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Operations. Robert Half International Inc. (the “Company”) provides specialized staffing and risk consulting services through such divisions as Accountemps ® , Robert Half ® Finance & Accounting , OfficeTeam ® , Robert Half ® Technology , Robert Half ® Management Resources , Robert Half ® Legal , The Creative Group ® , and Protiviti ® . The Company, through its Accountemps , Robert Half Finance & Accounting , and Robert Half Management Resources divisions, is a specialized provider of temporary, full-time, and senior-level project professionals in the fields of accounting and finance. OfficeTeam specializes in highly skilled temporary administrative support professionals. Robert Half Technology provides project and full-time technology professionals. Robert Half Legal provides temporary, project, and full-time staffing of lawyers, paralegals and legal support personnel. The Creative Group provides interactive, design, marketing, advertising and public relations professionals. Protiviti is a global consulting firm that helps companies solve problems in finance, technology, operations, data, analytics, governance, risk and internal audit, and is a wholly owned subsidiary of the Company. Revenues are predominantly derived from specialized staffing services. The Company operates in North America, South America, Europe, Asia and Australia. The Company is a Delaware corporation. Basis of Presentation. The Consolidated Financial Statements (“Financial Statements”) of the Company are prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and the rules of the Securities and Exchange Commission (“SEC”). Principles of Consolidation. The Financial Statements include the accounts of the Company and its subsidiaries, all of which are wholly owned. All intercompany balances have been eliminated. Use of Estimates. The preparation of financial statements in conformity with GAAP 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. As of December 31, 2017 , such estimates included allowances for uncollectible accounts receivable, workers’ compensation losses and income and other taxes. Management estimates are also utilized in the Company’s goodwill impairment assessment and in the valuation of stock grants subject to market conditions. Actual results and outcomes may differ from management's estimates and assumptions. Revenue Recognition. The Company derives its revenues from three segments: temporary and consultant staffing, permanent placement staffing, and risk consulting and internal audit services. Net service revenues as presented on the Consolidated Statements of Operations represent services rendered to customers less sales adjustments and allowances. Reimbursements, including those related to travel and out-of-pocket expenses, are also included in net service revenues, and equivalent amounts of reimbursable expenses are included in direct costs of services. The Company records revenue on a gross basis as a principal versus on a net basis as an agent in the presentation of revenues and expenses. The Company has concluded that gross reporting is appropriate because the Company (i) has the risk of identifying and hiring qualified employees, (ii) has the discretion to select the employees and establish their price and duties and (iii) bears the risk for services that are not fully paid for by customers. Temporary and consultant staffing revenues—Temporary and consultant staffing revenues are recognized when the services are rendered by the Company’s temporary employees. Employees placed on temporary assignment by the Company are the Company’s legal employees while they are working on assignments. The Company pays all related costs of employment, including workers’ compensation insurance, state and federal unemployment taxes, social security and certain fringe benefits. The Company assumes the risk of acceptability of its employees to its customers. Permanent placement staffing revenues—Permanent placement staffing revenues are recognized when employment candidates accept offers of permanent employment. The Company has a substantial history of estimating the effect of permanent placement candidates who do not remain with its clients through the 90-day guarantee period. Allowances are established to estimate these losses. Fees to clients are generally calculated as a percentage of the new employee’s annual compensation. No fees for permanent placement services are charged to employment candidates. Risk consulting and internal audit revenues—Risk consulting and internal audit services are generally provided on a time-and-material basis or fixed-fee basis. Revenues earned under time-and-material arrangements and fixed-fee arrangements are recognized using a proportional performance method as hours are incurred relative to total estimated hours for the engagement. The Company periodically evaluates the need to provide for any losses on these projects, and losses are recognized when it is probable that a loss will be incurred. Costs of Services. Direct costs of temporary and consultant staffing consist of payroll, payroll taxes and benefit costs for the Company’s temporary employees, as well as reimbursable expenses. Direct costs of permanent placement staffing services consist of reimbursable expenses. Risk consulting and internal audit costs of services include professional staff payroll, payroll taxes and benefit costs, as well as reimbursable expenses. Advertising Costs. The Company expenses all advertising costs as incurred. Advertising costs for the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Advertising Costs $ 49,433 $ 47,312 $ 44,015 Comprehensive Income. Comprehensive income includes net income and certain other items that are recorded directly to Stockholders’ Equity. The Company’s only source of other comprehensive income is foreign currency translation adjustments. Fair Value of Financial Instruments. The Company does not have any financial instruments which require re-measurement to fair value. The carrying values of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses represent fair value based upon their short-term nature. Cash and Cash Equivalents. The Company considers all highly liquid investments with a maturity at the date of purchase of three months or less as cash equivalents. Goodwill and Intangible Assets . Goodwill and intangible assets primarily consist of the cost of acquired companies in excess of the fair market value of their net tangible assets at the date of acquisition. Identifiable intangible assets are amortized over their lives, typically ranging from two to five years . Goodwill is not amortized, but is tested at least annually for impairment. The Company completed its annual goodwill impairment analysis as of June 30 in each of the three years ended December 31, 2017 , and determined that no adjustment to the carrying value of goodwill was required. There were no events or changes in circumstances during the six months ended December 31, 2017 that caused the Company to perform an interim impairment assessment. Income Tax Assets and Liabilities . In establishing its deferred income tax assets and liabilities, the Company makes judgments and interpretations based on the enacted tax laws and published tax guidance that are applicable to its operations. Deferred tax assets and liabilities are measured and recorded using current enacted tax rates, which the Company expects will apply to taxable income in the years in which those temporary differences are recovered or settled. The likelihood of a material change in the Company’s expected realization of these assets is dependent on future taxable income, its ability to use foreign tax credit carryforwards and carrybacks, final U.S. and foreign tax settlements, and the effectiveness of its tax planning strategies in the various relevant jurisdictions. On December 22, 2017, the President signed the Tax Cuts and Jobs Act (“TCJA”) into law. Effective January 1, 2018, among other changes, TCJA reduces the federal corporate tax rate to 21 percent, provides for a deemed repatriation and taxation at reduced rates of certain foreign earnings, and establishes new mechanisms to tax certain foreign earnings going forward. Similar to other large multinational companies, TCJA has wide ranging implications for the Company. The Company has recorded provisional amounts and a reasonable estimate of TCJA’s impact on its financial statements. As guidance regarding implementation of various provisions of TCJA is released by the U.S. Government over the course of 2018, the Company’s estimates may need to be adjusted accordingly. In December 2017, the SEC issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”), which allows the Company to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. Since TCJA was passed late in the fourth quarter of 2017, and ongoing guidance and accounting interpretations are expected over the next 12 months, the Company considers the accounting of the transition tax, deferred tax remeasurements, and other items to be incomplete due to the forthcoming guidance and ongoing analysis of its final tax positions for the year ended December 31, 2017. The Company expects to complete its analysis within the measurement period in accordance with SAB 118. The Company also evaluates the need for valuation allowances to reduce the deferred tax assets to realizable amounts. Management evaluates all positive and negative evidence and uses judgment regarding past and future events, including operating results, to help determine when it is more likely than not that all or some portion of the deferred tax assets may not be realized. When appropriate, a valuation allowance is recorded against deferred tax assets to offset future tax benefits that may not be realized. Valuation allowances of $20.2 million and $18.9 million were recorded as of December 31, 2017 and 2016 , respectively. The valuation allowances recorded related primarily to net operating losses in certain foreign operations. If such losses are ultimately utilized to offset future operating income, the Company will recognize a tax benefit up to the full amount of the valuation reserve. Workers’ Compensation . Except for states which require participation in state-operated insurance funds, the Company retains the economic burden for the first $0.5 million per occurrence in workers’ compensation claims. Workers’ compensation includes ongoing healthcare and indemnity coverage for claims and may be paid over numerous years following the date of injury. Claims in excess of $0.5 million are insured. Workers’ compensation expense includes the insurance premiums for claims in excess of $0.5 million , claims administration fees charged by the Company’s workers’ compensation administrator, premiums paid to state-operated insurance funds, and an estimate for the Company’s liability for Incurred But Not Reported (“IBNR”) claims and for the ongoing development of existing claims. The reserves for IBNR claims and for the ongoing development of existing claims in each reporting period includes estimates. The Company has established reserves for workers’ compensation claims using loss development rates which are estimated using periodic third party actuarial valuations based upon historical loss statistics which include the Company’s historical frequency and severity of workers’ compensation claims, and an estimate of future cost trends. While management believes that its assumptions and estimates are appropriate, significant differences in actual experience or significant changes in assumptions may materially affect the Company’s future results. Foreign Currency Translation. The reporting currency of the Company and its subsidiaries is the U.S. dollar. The functional currency of the Company's foreign subsidiaries is their local currency. The results of operations of the Company’s foreign subsidiaries are translated at the monthly average exchange rates prevailing during the period. The financial position of the Company’s foreign subsidiaries is translated at the current exchange rates at the end of the period, and the related translation adjustments are recorded as a component of accumulated other comprehensive income within Stockholders’ Equity. Gains and losses resulting from foreign currency transactions are included as a component of selling, general and administrative expenses in the Consolidated Statements of Operations, and have not been material for all periods presented. Stock-based Compensation . Under various stock plans, officers, employees and outside directors have received or may receive grants of restricted stock, stock units, stock appreciation rights or options to purchase common stock. The Company recognizes compensation expense equal to the grant-date fair value for all stock-based payment awards that are expected to vest. This expense is recorded on a straight-line basis over the requisite service period of the entire award, unless the awards are subject to performance conditions, in which case the Company recognizes compensation expense over the requisite service period of each separate vesting tranche. The Company determines the grant-date fair value of its restricted stock and stock unit awards using the fair market value of its stock on the grant date, unless the awards are subject to market conditions, in which case the Company utilizes a binomial-lattice model (i.e., Monte Carlo simulation model). The Monte Carlo simulation model utilizes multiple input variables to determine the stock-based compensation expense. No stock appreciation rights have been granted under the Company’s existing stock plans. The Company has not granted any options to purchase common stock since 2006. Property and Equipment . Property and equipment are recorded at cost. Depreciation expense is computed using the straight-line method over the following useful lives: Computer hardware 2 to 3 years Computer software 2 to 5 years Furniture and equipment 5 years Leasehold improvements Term of lease, 5 years maximum Internal-use Software. The Company capitalizes direct costs incurred in the development of internal-use software. Amounts capitalized are reported as a component of computer software within property and equipment. Internal-use software development costs capitalized for the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Internal-use software development costs $ 9,030 $ 33,753 $ 31,964

New Accounting Pronouncements

New Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted Accounting Pronouncements Stock Compensation. In March 2016, the Financial Accounting Standards Board (“FASB”) issued authoritative guidance which changes financial reporting as it relates to Employee Share-Based Payment Accounting. Under the new guidance, several aspects of the accounting for share-based payment award transactions will be simplified, including: i) income tax consequences; ii) classification of awards as either equity or liabilities; and iii) classification on the statement of cash flows. The new guidance was effective for annual and interim periods beginning after December 15, 2016 and was adopted by the Company effective January 1, 2017. The adoption of this guidance did not have a material impact on the Company’s financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted Revenue from Contracts with Customers. In May 2014, the FASB issued authoritative guidance that provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The new guidance requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. It also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. The amended guidance also requires additional quantitative and qualitative disclosures. In March 2016, amended guidance was issued to clarify implementation guidance on principal versus agent consideration. In April 2016 an amendment provided clarifications on determining whether a promised license provides a customer with a right to use or a right to access an entity’s intellectual property. In May 2016 an amendment provided narrow scope improvements and practical expedients to reduce the potential diversity, cost and complexity of applying new revenue standard. These amendments, as well as the original guidance, are all effective for annual and interim periods beginning after December 15, 2017. The new standard was adopted by the Company effective January 1, 2018. The standard is required to be adopted on either a full or modified retrospective basis. As the initial adoption of the standard did not have a material impact on the Company’s financial statements, prior periods will not be restated. The Company also had no significant changes to systems, processes, or controls. Lease Accounting. In February 2016, the FASB issued authoritative guidance which changes financial reporting as it relates to leasing transactions. Under the new guidance, lessees will be required to recognize a lease liability, measured on a discounted basis; and a right-of-use asset, for the lease term. The new guidance is effective for annual and interim periods beginning after December 15, 2018. Early application is permitted for all entities upon issuance. Lessees and lessors must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. While the impact of the adoption of this guidance will include the recognition of right-of-use assets and lease liabilities on the Company’s statement of financial position, the Company is in the process of evaluating the impact of adoption of this guidance on its systems, processes, and controls. Classification of Certain Cash Receipts and Cash Payments in Statement of Cash Flows. In August 2016, the FASB issued authoritative guidance designed to address diversity in how certain cash receipts and cash payments are presented and classified in the statement of cash flows, including: i) contingent consideration payments made after a business combination; ii) proceeds from the settlement of insurance claims; and iii) proceeds from the settlement of corporate-owned life insurance policies. The new guidance is effective for the Company for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted in any interim or annual period. The Company believes the adoption of this guidance will not have a material impact on its financial statements. Simplifying the Test for Goodwill Impairment. In January 2017, the FASB issued authoritative guidance to simplify the goodwill impairment testing process. The new standard eliminates Step 2 of the goodwill impairment test. If a company determines in Step 1 of the goodwill impairment test that the carrying value of goodwill is greater than the fair value, an impairment in that amount should be recorded to the income statement, rather than proceeding to Step 2. The new guidance is effective for the Company beginning after December 31, 2019, although early adoption is permitted. The Company believes the adoption of this guidance will not have a material impact on its financial statements. Stock Compensation. In May 2017, the FASB issued authoritative guidance updating which changes in the terms or conditions of a share-based payment award require an entity to apply modification accounting. Under the amended guidance, entities are required to account for the effects of a modification if the fair value, vesting conditions or classification (as an equity instrument or a liability instrument) of the modified award change from that of the original award immediately before the modification. The new guidance is effective for the Company in interim or annual periods beginning after December 15, 2017. The Company believes the adoption of this guidance will not have a material impact on its financial statements.

Other Current Assets

Other Current Assets	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Current Assets	Other Current Assets Other current assets consisted of the following (in thousands): December 31, 2017 2016 Deposits in trusts for employee deferred compensation plans $ 292,326 $ 236,371 Other 112,385 84,434 Other current assets $ 404,711 $ 320,805

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill The following table sets forth the activity in goodwill from December 31, 2015 , through December 31, 2017 (in thousands): Goodwill Temporary and consultant staffing Permanent placement staffing Risk consulting and internal audit services Total Balance as of December 31, 2015 $ 133,173 $ 26,251 $ 49,155 $ 208,579 Acquisitions 1,248 — 299 1,547 Foreign currency translation adjustments (546 ) (236 ) 449 (333 ) Balance as of December 31, 2016 $ 133,875 $ 26,015 $ 49,903 $ 209,793 Foreign currency translation adjustments 613 144 335 1,092 Balance as of December 31, 2017 $ 134,488 $ 26,159 $ 50,238 $ 210,885

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Computer hardware $ 171,515 $ 170,746 Computer software 376,761 374,490 Furniture and equipment 102,424 100,472 Leasehold improvements 148,764 133,541 Other 9,907 9,993 Property and equipment, cost 809,371 789,242 Accumulated depreciation (664,484 ) (627,733 ) Property and equipment, net $ 144,887 $ 161,509

Accrued Payroll and Benefit Cos

Accrued Payroll and Benefit Costs	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued Payroll and Benefit Costs	Accrued Payroll and Benefit Costs Accrued payroll and benefit costs consisted of the following (in thousands): December 31, 2017 2016 Payroll and benefits $ 256,804 $ 243,301 Employee deferred compensation plans 312,429 252,349 Workers’ compensation 17,092 19,361 Payroll taxes 26,574 24,037 Accrued payroll and benefit costs $ 612,899 $ 539,048 Included in employee deferred compensation plans is the following (in thousands): December 31, 2017 2016 Deferred compensation plan and other benefits related to the Company’s Chief Executive Officer $ 86,145 $ 83,899

Notes Payable and Other Indebte

Notes Payable and Other Indebtedness	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Notes Payable and Other Indebtedness	Notes Payable and Other Indebtedness The Company issued promissory notes as well as other forms of indebtedness in connection with certain acquisitions and other payment obligations. These notes are due in varying installments and, in aggregate, amounted to $0.8 million at December 31, 2017 , and $1.0 million at December 31, 2016 . At December 31, 2017 , $0.8 million of the notes were collateralized by a standby letter of credit. The following table shows the schedule of maturities for notes payable and other indebtedness at December 31, 2017 (in thousands): 2018 $ 183 2019 200 2020 218 2021 239 2022 — $ 840 At December 31, 2017 , the notes carried fixed rates and the weighted average interest rate for the above was 9.0% for each of the years ended December 31, 2017 , 2016 and 2015 . The Company has an uncommitted letter of credit facility (the “facility”) of up to $35.0 million , which is available to cover the issuance of debt support standby letters of credit. The Company had used $17.4 million in debt support standby letters of credit as of December 31, 2017 and $15.8 million as of December 31, 2016 . Of the debt support standby letters of credit outstanding, $16.6 million as of December 31, 2017 and $14.8 million as of December 31, 2016 , satisfies workers’ compensation insurer’s collateral requirements. There is a service fee of 1.125% on the used portion of the facility. The facility is subject to certain financial covenants and expires on August 31, 2018. The Company was in compliance with these covenants as of December 31, 2017 . The Company intends to renew this facility prior to its August 31, 2018 expiration.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company recorded provisional amounts and a reasonable estimate in its provision for income taxes and estimated deferred tax assets, for the impact of TCJA. The provision (benefit) for income taxes for the years ended December 31, 2017 , 2016 and 2015 , consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Current: Federal $ 133,097 $ 156,937 $ 181,640 State 24,944 34,927 36,281 Foreign 27,079 20,725 13,892 Deferred: Federal and state 41,717 (3,785 ) (8,398 ) Foreign 95 1,917 (181 ) $ 226,932 $ 210,721 $ 223,234 Income before the provision for income taxes for the years ended December 31, 2017 , 2016 and 2015 , consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Domestic $ 445,418 $ 494,890 $ 528,916 Foreign 72,098 59,220 52,114 $ 517,516 $ 554,110 $ 581,030 The income taxes shown above varied from the statutory federal income tax rates for these periods as follows: Years Ended December 31, 2017 2016 2015 Federal U.S. income tax rate 35.0 % 35.0 % 35.0 % State income taxes, net of federal tax benefit 3.7 4.2 4.2 Non-deductible expenses 0.4 0.5 0.5 Non-U.S. income taxed at different rates, net of foreign tax credits — (0.6 ) 0.1 Federal tax credits (1.3 ) (0.8 ) (0.6 ) Tax impact of uncertain tax positions 0.2 — (0.2 ) Valuation allowance release, net — (0.1 ) (0.5 ) Tax effects of TCJA 6.5 — — Other, net (0.6 ) (0.2 ) (0.1 ) Effective tax rate 43.9 % 38.0 % 38.4 % In accordance with TCJA, the Company remeasured certain deferred tax assets and liabilities, based on the rates at which they are expected to reverse in the future. The Company is still analyzing certain aspects of TCJA and refining our calculation, which could potentially affect the measurement of these balances or give rise to different deferred tax amounts. The provisional amount and reasonable estimate recorded related to the re-measurement of the Company’s deferred tax balance was $34.6 million . The Company recorded provisional amounts and a reasonable estimate for the one-time transition tax on its total post-1986 foreign earnings and profits, as required by TCJA. A provisional amount of $7.7 million in connection with the transition tax is offset by foreign tax credits in the Company's current income tax expense. The Company anticipates additional guidance will be released by the government throughout 2018 that may require the Company to adjust this estimate during the measurement period prescribed by SAB 118. No additional income taxes have been provided for any remaining undistributed foreign earnings not subject to the transition tax, or any additional outside basis differences inherent in our foreign entities, as the Company is still in the process of evaluating its foreign cash needs, and how much, if any, of the amount of earnings should be considered indefinitely reinvested. The deferred portion of the tax provision (benefit) consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Amortization of franchise rights $ 495 $ 500 $ 514 Amortization of other intangibles 1,193 1,221 1,590 Accrued expenses, deducted for tax when paid 15,213 (6,889 ) (17,664 ) Capitalized costs for books, deducted for tax (5,790 ) 5,901 5,315 Depreciation (4,079 ) (2,405 ) (5,932 ) Federal impact of unrecognized tax benefits 39 75 1,058 Foreign tax credit carryforwards — — 3,636 Tax effects of TCJA 34,633 — — Other, net 108 (271 ) 2,904 $ 41,812 $ (1,868 ) $ (8,579 ) The components of the deferred income tax amounts at December 31, 2017 and 2016 , were as follows (in thousands): December 31, 2017 2016 Deferred Income Tax Assets Provision for bad debts $ 6,794 $ 10,510 Deferred compensation and other benefit obligations 68,101 112,811 Workers’ compensation 3,127 5,634 Stock-based compensation 8,614 16,772 Credits and net operating loss carryforwards 30,087 30,534 Other 13,343 18,116 Total deferred income tax assets 130,066 194,377 Deferred Income Tax Liabilities Amortization of intangible assets (20,220 ) (28,681 ) Property and equipment basis differences (4,421 ) (16,640 ) Other (10,847 ) (11,658 ) Total deferred income tax liabilities (35,488 ) (56,979 ) Valuation allowance (20,178 ) (18,907 ) Total deferred income tax assets, net $ 74,400 $ 118,491 Credits and net operating loss carryforwards primarily include net operating losses in foreign countries of $26.4 million that expire in 2018 and later ; and California enterprise zone tax credits of $3.5 million that expire in 2023 . Of the $3.5 million of California enterprise zone tax credits, the Company expects that it will utilize $2.0 million of these credits prior to expiration. Valuation allowances of $18.7 million have been established for net operating loss carryforwards and other deferred items in foreign countries. In addition, a valuation allowance of $1.5 million has been established for California enterprise zone tax credits. FASB authoritative guidance prescribes a recognition threshold and measurement attribute criteria for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The literature also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. The following table reconciles the total amounts of gross unrecognized tax benefits from January 1, 2015 to December 31, 2017 (in thousands): December 31, 2017 2016 2015 Balance at beginning of period $ 731 $ 814 $ 4,573 Gross increases—tax positions in prior years 1,503 92 — Gross decreases—tax positions in prior years (257 ) — (1,807 ) Gross increases—tax positions in current year 956 114 120 Settlements (40 ) — (520 ) Lapse of statute of limitations (7 ) (289 ) (1,552 ) Balance at end of period $ 2,886 $ 731 $ 814 The total amount of unrecognized tax benefits that, if recognized, would impact the effective tax rate is $2.8 million , $0.5 million and $0.5 million for 2017 , 2016 and 2015 , respectively. The Company’s continuing practice is to recognize interest and penalties related to income tax matters in income tax expense. The total amount of interest and penalties accrued is $0.1 million as of December 31, 2017 . The total amount of interest and penalties accrued as of December 31, 2016 is $0.1 million , including a $0.1 million reduction recorded in income tax expense during the year. The total amount of interest and penalties accrued as of December 31, 2015 , was $0.2 million , including a $2.3 million reduction recorded in income tax expense during the year. The Company believes it is reasonably possible that the settlement of certain tax uncertainties could occur within the next twelve months; accordingly, $0.1 million of the unrecognized gross tax benefit has been classified as a current liability as of December 31, 2017 . This amount primarily represents unrecognized tax benefits composed of items related to assessed state income tax audits and negotiations. The Company’s major income tax jurisdictions are the United States, Australia, Belgium, Canada, France, Germany and the United Kingdom. For U.S. federal income tax, the Company remains subject to examination for 2014 and subsequent years. For major U.S. states, with few exceptions, the Company remains subject to examination for 2013 and subsequent years. Generally, for the foreign countries, the Company remains subject to examination for 2010 and subsequent years.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Rental expense, primarily for office premises, amounted to $87.5 million , $87.3 million and $85.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The approximate minimum rental commitments for 2018 and thereafter under non-cancelable leases in effect at December 31, 2017 were as follows (in thousands): 2018 $ 85,484 2019 73,763 2020 64,221 2021 47,107 2022 35,535 Thereafter 64,042 $ 370,152 On March 13, 2014, Plaintiff Leonor Rodriguez, on her own behalf and on behalf of a putative class of allegedly similarly situated individuals, filed a complaint against the Company in the Superior Court of California, San Diego County. The complaint alleges that a putative class of current and former employees of the Company working in California since March 13, 2011 were denied compensation for the time they spent interviewing with clients of the Company as well as performing activities related to the interview process. Rodriguez seeks recovery on her own behalf and on behalf of the putative class in an unspecified amount for this allegedly unpaid compensation. Rodriguez also seeks recovery of an unspecified amount for the alleged failure of the Company to provide her and the putative class with accurate wage statements. Rodriguez also seeks an unspecified amount of other damages, attorneys’ fees, and statutory penalties, including but not limited to statutory penalties on behalf of herself and other allegedly “aggrieved employees” as defined by California’s Labor Code Private Attorney General Act (“PAGA”). On October 10, 2014, the Court granted a motion by the Company to compel all of Rodriguez’s claims, except the PAGA claim, to individual arbitration. At this stage of the litigation, it is not feasible to predict the outcome of or a range of loss, should a loss occur, from this proceeding and, accordingly, no amounts have been provided in the Company’s Financial Statements. The Company believes it has meritorious defenses to the allegations and the Company intends to continue to vigorously defend against the litigation. On March 23, 2015, Plaintiff Jessica Gentry, on her own behalf and on behalf of a putative class of allegedly similarly situated individuals, filed a complaint against the Company in the Superior Court of California, San Francisco County, which was subsequently amended on October 23, 2015. The complaint, which was filed by the same plaintiffs’ law firm that brought the Rodriguez matter described above, alleges claims similar to those alleged in Rodriguez. Specifically, the complaint alleges that a putative class of current and former employees of the Company working in California since March 13, 2010 were denied compensation for the time they spent interviewing “for temporary and permanent employment opportunities” as well as performing activities related to the interview process. Gentry seeks recovery on her own behalf and on behalf of the putative class in an unspecified amount for this allegedly unpaid compensation. Gentry also seeks recovery of an unspecified amount for the alleged failure of the Company to provide her and the putative class with accurate wage statements. Gentry also seeks an unspecified amount of other damages, attorneys’ fees, and statutory penalties, including penalties for allegedly not paying all wages due upon separation to former employees and statutory penalties on behalf of herself and other allegedly “aggrieved employees” as defined by PAGA. On January 4, 2016, the Court denied a motion by the Company to compel all of Gentry’s claims, except the PAGA claim, to individual arbitration. At this stage of the litigation, it is not feasible to predict the outcome of or a range of loss, should a loss occur, from this proceeding and, accordingly, no amounts have been provided in the Company’s Financial Statements. The Company believes it has meritorious defenses to the allegations and the Company intends to continue to vigorously defend against the litigation. The Company is involved in a number of other lawsuits arising in the ordinary course of business. While management does not expect any of these other matters to have a material adverse effect on the Company’s results of operations, financial position or cash flows, litigation is subject to certain inherent uncertainties. Legal costs associated with the resolution of claims, lawsuits and other contingencies are expensed as incurred.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Stock Repurchase Program. As of December 31, 2017 , the Company is authorized to repurchase, from time to time, up to 2.3 million additional shares of the Company’s common stock on the open market or in privately negotiated transactions, depending on market conditions. The number and the cost of common stock shares repurchased during the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Common stock repurchased (in shares) 4,046 4,046 4,343 Common stock repurchased $ 196,645 $ 163,614 $ 228,166 Additional stock repurchases were made in connection with employee stock plans, whereby Company shares were tendered by employees for the payment of exercise price and applicable statutory withholding taxes. The number and the cost of employee stock plan repurchases made during the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Repurchases related to employee stock plans (in shares) 408 359 474 Repurchases related to employee stock plans $ 20,391 $ 15,170 $ 24,755 The repurchased shares are held in treasury and are presented as if constructively retired. Treasury stock is accounted for using the cost method. Treasury stock activity for each of the three years ended December 31, 2017 , 2016 and 2015 (consisting of stock option exercises and the purchase of shares for the treasury) is presented in the Consolidated Statements of Stockholders’ Equity. Cash Dividends. The Company’s Board of Directors may at their discretion declare and pay dividends upon the shares of the Company’s stock either out of the Company’s retained earnings or capital surplus. The cash dividends declared during the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table: Years Ended December 31, 2017 2016 2015 Cash dividends declared per share $ .96 $ .88 $ .80 Repurchases of shares and issuances of cash dividends are applied first to the extent of retained earnings and any remaining amounts are applied to capital surplus.

Stock Plans

Stock Plans	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Plans	Stock Plans Under various stock plans, officers, employees, and outside directors have received or may receive grants of restricted stock, stock units, stock appreciation rights or options to purchase common stock. Grants have been made at the discretion of the Committees of the Board of Directors. Grants generally vest either on a straight-line basis over four years or on a cliff basis over three years. Shares offered under the plan are authorized but unissued shares or treasury shares. Recipients of restricted stock do not pay any cash consideration to the Company for the shares, have the right to vote all shares subject to such grant, and there were no grants outstanding that received dividends prior to vesting. Restricted stock grants made on or after July 28, 2009, contain forfeitable rights to dividends. Dividends for these grants are accrued on the dividend payment dates but are not paid until the shares vest, and dividends accrued for shares that ultimately do not vest are forfeited. Recipients of stock units do not pay any cash consideration for the units, do not have the right to vote, and do not receive dividends with respect to such units. The Company recognizes compensation expense equal to the grant-date fair value for all stock-based payment awards that are expected to vest. This expense is recorded on a straight-line basis over the requisite service period of the entire award, unless the awards are subject to performance conditions, in which case the Company recognizes compensation expense over the requisite service period of each separate vesting tranche. The Company determines the grant-date fair value of its restricted stock and stock unit awards using the fair market value on the grant date, unless the awards are subject to market conditions, in which case the Company utilizes a binomial-lattice model (i.e., Monte Carlo simulation model). The Monte Carlo simulation model utilizes multiple input variables to determine the stock-based compensation expense. During the year ended December 31, 2017 , the Company granted performance shares to its executives in the form of restricted stock. The shares granted contain (1) a performance condition based earnings per share, and (2) a performance condition based on Return on Invested Capital (“ROIC”). The ROIC performance condition measures the Company’s performance against a peer group. Shares will be delivered at the end of the three year vesting and ROIC performance period based on the Company’s actual performance compared to the peer group. Actual shares earned will range from seventy-five percent ( 75% ) to one hundred twenty-five percent ( 125% ) of the target award after any adjustment made for the EPS performance condition. Stock-based compensation expense consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Restricted stock and stock units - expense $ 42,191 $ 42,699 $ 41,292 Unrecognized compensation cost is expected to be recognized over the next four years . Total unrecognized compensation cost, net of estimated forfeitures, consisted of the following (in thousands): December 31, 2017 2016 2015 Restricted stock and stock units - unrecognized future costs $ 62,730 $ 60,481 $ 60,627 The following table reflects activity under all stock plans from December 31, 2014 through December 31, 2017 , and the weighted average exercise prices (in thousands, except per share amounts): Restricted Stock Plans without Market-Condition Restricted Stock Plans with Market-Condition Stock Option Plans Number of Shares/ Units Weighted Average Grant Date Fair Value Number of Shares/ Units Weighted Average Grant Date Fair Value Number of Shares/ Units Weighted Average Exercise Price Per Share Outstanding, December 31, 2014 1,165 $36.47 1,234 $40.24 77 $29.22 Granted 502 $58.14 257 $71.86 — — Exercised — — — — (54 ) $28.18 Restrictions lapsed (599 ) $36.30 (499 ) $31.41 — — Forfeited (16 ) $37.63 — — (11 ) $30.94 Outstanding, December 31, 2015 1,052 $46.88 992 $52.89 12 $32.36 Granted 772 $38.47 358 $45.93 — — Exercised — — — — (7 ) $32.36 Restrictions lapsed (545 ) $42.42 (364 ) $43.04 — — Forfeited (36 ) $41.28 (36 ) $43.04 (5 ) $32.36 Outstanding, December 31, 2016 1,243 $43.78 950 $54.42 — — Granted 904 $47.86 50 $50.09 — — Exercised — — — — — — Restrictions lapsed (616 ) $44.09 (384 ) $50.09 — — Forfeited (41 ) $43.68 — — — — Outstanding, December 31, 2017 1,490 $46.13 616 $56.76 — — The total pre-tax intrinsic value of stock options exercised and the total fair value of shares vested during the years ended December 31, 2017 , 2016 and 2015, are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Total pre-tax intrinsic value of stock options exercised $ — $ 52 $ 1,709 Total fair value of shares vested $ 50,385 $ 39,302 $ 56,570 At December 31, 2017 , the total number of available shares to grant under the plans (consisting of either restricted stock, stock units, stock appreciation rights or options to purchase common stock) was approximately 3.8 million .

Net Income Per Share

Net Income Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Per Share	Net Income Per Share The calculation of net income per share for the three years ended December 31, 2017 is reflected in the following table (in thousands, except per share amounts): Years Ended December 31, 2017 2016 2015 Net income $ 290,584 $ 343,389 $ 357,796 Basic: Weighted average shares 124,152 127,991 131,749 Diluted: Weighted average shares 124,152 127,991 131,749 Dilutive effect of potential common shares 740 775 1,181 Diluted weighted average shares 124,892 128,766 132,930 Net income per share: Basic $ 2.34 $ 2.68 $ 2.72 Diluted $ 2.33 $ 2.67 $ 2.69 Potential common shares include the dilutive effect of stock options, unvested performance-based restricted stock, restricted stock which contains forfeitable rights to dividends, and stock units. Employee stock options will have a dilutive effect under the treasury method only when the respective period’s average market value of the Company’s common stock exceeds the exercise proceeds. Under the treasury method, exercise proceeds include the amount the employee must pay for exercising stock options, the amount of compensation cost for future service that the Company has not yet recognized, and the amount of tax benefits that would be recorded in capital surplus, if the options were exercised and the stock units and performance-based restricted stock had vested.

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments	Business Segments The Company, which aggregates its operating segments based on the nature of services, has three reportable segments: temporary and consultant staffing, permanent placement staffing, and risk consulting and internal audit services. The temporary and consultant staffing segment provides specialized staffing in the accounting and finance, administrative and office, information technology, legal, advertising, marketing and web design fields. The permanent placement staffing segment provides full-time personnel in the accounting, finance, administrative and office, and information technology fields. The risk consulting segment provides business and technology risk consulting and internal audit services. The accounting policies of the segments are set forth in Note A—Summary of Significant Accounting Policies. The Company evaluates performance based on income from operations before net interest income, intangible amortization expense, and income taxes. The following table provides a reconciliation of revenue and operating income by reportable segment to consolidated results (in thousands): Years Ended December 31, 2017 2016 2015 Net service revenues Temporary and consultant staffing $ 4,011,042 $ 4,026,777 $ 3,930,843 Permanent placement staffing 439,214 419,314 421,411 Risk consulting and internal audit services 816,533 804,308 742,679 $ 5,266,789 $ 5,250,399 $ 5,094,933 Operating income Temporary and consultant staffing $ 355,700 $ 393,704 $ 399,808 Permanent placement staffing 77,673 80,001 85,019 Risk consulting and internal audit services 83,907 80,754 95,845 517,280 554,459 580,672 Amortization of intangible assets 1,563 1,237 192 Interest income, net (1,799 ) (888 ) (550 ) Income before income taxes $ 517,516 $ 554,110 $ 581,030 Assets by reportable segment are not presented as the Company does not allocate assets to its reportable segments, nor is such information used by management for purposes of assessing performance or allocating resources. The Company operates internationally, with operations in North America, South America, Europe, Asia and Australia. The following tables represent revenues and long-lived assets by geographic location (in thousands): Years Ended December 31, 2017 2016 2015 Net service revenues (a) Domestic $ 4,121,701 $ 4,220,477 $ 4,105,013 Foreign (b) 1,145,088 1,029,922 989,920 $ 5,266,789 $ 5,250,399 $ 5,094,933 December 31, 2017 2016 2015 Assets, long-lived Domestic $ 113,069 $ 136,434 $ 117,176 Foreign 31,818 25,075 25,730 $ 144,887 $ 161,509 $ 142,906 (a) There were no customers that accounted for more than 10% of the Company’s total net revenue in any year presented. (b) No individual country represented more than 10% of revenues in any year presented.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	Quarterly Financial Data (Unaudited) The following tabulation shows certain quarterly financial data for 2017 and 2016 (in thousands, except per share amounts): Quarter 2017 1 2 3 4 Net service revenues $ 1,287,370 $ 1,308,428 $ 1,324,709 $ 1,346,282 Gross margin $ 525,828 $ 538,438 $ 546,400 $ 553,146 Income before income taxes $ 125,501 $ 130,707 $ 132,270 $ 129,038 Net income $ 78,521 $ 80,316 $ 84,700 $ 47,047 Basic net income per share $ .63 $ .64 $ .69 $ .38 Diluted net income per share $ .62 $ .64 $ .68 $ .38 Quarter 2016 1 2 3 4 Net service revenues $ 1,302,625 $ 1,344,160 $ 1,338,541 $ 1,265,073 Gross margin $ 531,972 $ 556,993 $ 552,509 $ 519,202 Income before income taxes $ 133,791 $ 149,414 $ 146,324 $ 124,581 Net income $ 83,416 $ 91,616 $ 90,569 $ 77,788 Basic net income per share $ .65 $ .71 $ .71 $ .61 Diluted net income per share $ .64 $ .71 $ .71 $ .61

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 13, 2018, the Company authorized the repurchase, from time to time, of up to an additional 10 million shares of the Company's common stock on the open market or in privately negotiated transactions, depending on market conditions. The authorization is in addition to the approximately 2.3 million shares remaining under the existing repurchase program. There is no guarantee as to whether, when, or how many shares the Company will repurchase, and the Company may discontinue the repurchase program at any time. On February 13, 2018, the Company announced the following: Quarterly dividend per share $.28 Declaration date February 13, 2018 Record date February 23, 2018 Payment date March 15, 2018

Schedule II-Valuation and Quali

Schedule II-Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II-Valuation and Qualifying Accounts	Schedule II—Valuation and Qualifying Accounts (in thousands) Balance at Beginning of Period Charged to Expenses Deductions Translation Adjustments Balance at End of Period Year Ended December 31, 2015 Allowance for doubtful accounts receivable $ 30,544 12,005 (5,353 ) (2,109 ) $ 35,087 Deferred tax valuation allowance $ 29,561 6,283 (8,068 ) (1,447 ) $ 26,329 Year Ended December 31, 2016 Allowance for doubtful accounts receivable $ 35,087 9,192 (9,907 ) (1,239 ) $ 33,133 Deferred tax valuation allowance $ 26,329 2,160 (9,517 ) (65 ) $ 18,907 Year Ended December 31, 2017 Allowance for doubtful accounts receivable $ 33,133 8,022 (8,751 ) 777 $ 33,181 Deferred tax valuation allowance $ 18,907 1,411 (1,275 ) 1,135 $ 20,178

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation. The Consolidated Financial Statements (“Financial Statements”) of the Company are prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and the rules of the Securities and Exchange Commission (“SEC”).
Principles of Consolidation	Principles of Consolidation. The Financial Statements include the accounts of the Company and its subsidiaries, all of which are wholly owned. All intercompany balances have been eliminated.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with GAAP 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. As of December 31, 2017 , such estimates included allowances for uncollectible accounts receivable, workers’ compensation losses and income and other taxes. Management estimates are also utilized in the Company’s goodwill impairment assessment and in the valuation of stock grants subject to market conditions. Actual results and outcomes may differ from management's estimates and assumptions.
Revenue Recognition	Revenue Recognition. The Company derives its revenues from three segments: temporary and consultant staffing, permanent placement staffing, and risk consulting and internal audit services. Net service revenues as presented on the Consolidated Statements of Operations represent services rendered to customers less sales adjustments and allowances. Reimbursements, including those related to travel and out-of-pocket expenses, are also included in net service revenues, and equivalent amounts of reimbursable expenses are included in direct costs of services. The Company records revenue on a gross basis as a principal versus on a net basis as an agent in the presentation of revenues and expenses. The Company has concluded that gross reporting is appropriate because the Company (i) has the risk of identifying and hiring qualified employees, (ii) has the discretion to select the employees and establish their price and duties and (iii) bears the risk for services that are not fully paid for by customers. Temporary and consultant staffing revenues—Temporary and consultant staffing revenues are recognized when the services are rendered by the Company’s temporary employees. Employees placed on temporary assignment by the Company are the Company’s legal employees while they are working on assignments. The Company pays all related costs of employment, including workers’ compensation insurance, state and federal unemployment taxes, social security and certain fringe benefits. The Company assumes the risk of acceptability of its employees to its customers. Permanent placement staffing revenues—Permanent placement staffing revenues are recognized when employment candidates accept offers of permanent employment. The Company has a substantial history of estimating the effect of permanent placement candidates who do not remain with its clients through the 90-day guarantee period. Allowances are established to estimate these losses. Fees to clients are generally calculated as a percentage of the new employee’s annual compensation. No fees for permanent placement services are charged to employment candidates. Risk consulting and internal audit revenues—Risk consulting and internal audit services are generally provided on a time-and-material basis or fixed-fee basis. Revenues earned under time-and-material arrangements and fixed-fee arrangements are recognized using a proportional performance method as hours are incurred relative to total estimated hours for the engagement. The Company periodically evaluates the need to provide for any losses on these projects, and losses are recognized when it is probable that a loss will be incurred.
Costs of Services	Costs of Services. Direct costs of temporary and consultant staffing consist of payroll, payroll taxes and benefit costs for the Company’s temporary employees, as well as reimbursable expenses. Direct costs of permanent placement staffing services consist of reimbursable expenses. Risk consulting and internal audit costs of services include professional staff payroll, payroll taxes and benefit costs, as well as reimbursable expenses.
Advertising Costs	Advertising Costs. The Company expenses all advertising costs as incurred.
Comprehensive Income	Comprehensive Income. Comprehensive income includes net income and certain other items that are recorded directly to Stockholders’ Equity. The Company’s only source of other comprehensive income is foreign currency translation adjustments.
Fair Value of Financial Instruments	Fair Value of Financial Instruments. The Company does not have any financial instruments which require re-measurement to fair value. The carrying values of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses represent fair value based upon their short-term nature.
Cash and Cash Equivalents	Cash and Cash Equivalents. The Company considers all highly liquid investments with a maturity at the date of purchase of three months or less as cash equivalents.
Goodwill and Intangible Assets	Goodwill and Intangible Assets . Goodwill and intangible assets primarily consist of the cost of acquired companies in excess of the fair market value of their net tangible assets at the date of acquisition. Identifiable intangible assets are amortized over their lives, typically ranging from two to five years . Goodwill is not amortized, but is tested at least annually for impairment. The Company completed its annual goodwill impairment analysis as of June 30 in each of the three years ended December 31, 2017 , and determined that no adjustment to the carrying value of goodwill was required. There were no events or changes in circumstances during the six months ended December 31, 2017 that caused the Company to perform an interim impairment assessment.
Income Tax Assets and Liabilities	Income Tax Assets and Liabilities . In establishing its deferred income tax assets and liabilities, the Company makes judgments and interpretations based on the enacted tax laws and published tax guidance that are applicable to its operations. Deferred tax assets and liabilities are measured and recorded using current enacted tax rates, which the Company expects will apply to taxable income in the years in which those temporary differences are recovered or settled. The likelihood of a material change in the Company’s expected realization of these assets is dependent on future taxable income, its ability to use foreign tax credit carryforwards and carrybacks, final U.S. and foreign tax settlements, and the effectiveness of its tax planning strategies in the various relevant jurisdictions. On December 22, 2017, the President signed the Tax Cuts and Jobs Act (“TCJA”) into law. Effective January 1, 2018, among other changes, TCJA reduces the federal corporate tax rate to 21 percent, provides for a deemed repatriation and taxation at reduced rates of certain foreign earnings, and establishes new mechanisms to tax certain foreign earnings going forward. Similar to other large multinational companies, TCJA has wide ranging implications for the Company. The Company has recorded provisional amounts and a reasonable estimate of TCJA’s impact on its financial statements. As guidance regarding implementation of various provisions of TCJA is released by the U.S. Government over the course of 2018, the Company’s estimates may need to be adjusted accordingly. In December 2017, the SEC issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”), which allows the Company to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. Since TCJA was passed late in the fourth quarter of 2017, and ongoing guidance and accounting interpretations are expected over the next 12 months, the Company considers the accounting of the transition tax, deferred tax remeasurements, and other items to be incomplete due to the forthcoming guidance and ongoing analysis of its final tax positions for the year ended December 31, 2017. The Company expects to complete its analysis within the measurement period in accordance with SAB 118. The Company also evaluates the need for valuation allowances to reduce the deferred tax assets to realizable amounts. Management evaluates all positive and negative evidence and uses judgment regarding past and future events, including operating results, to help determine when it is more likely than not that all or some portion of the deferred tax assets may not be realized. When appropriate, a valuation allowance is recorded against deferred tax assets to offset future tax benefits that may not be realized.
Workers' Compensation	Workers’ Compensation . Except for states which require participation in state-operated insurance funds, the Company retains the economic burden for the first $0.5 million per occurrence in workers’ compensation claims. Workers’ compensation includes ongoing healthcare and indemnity coverage for claims and may be paid over numerous years following the date of injury. Claims in excess of $0.5 million are insured. Workers’ compensation expense includes the insurance premiums for claims in excess of $0.5 million , claims administration fees charged by the Company’s workers’ compensation administrator, premiums paid to state-operated insurance funds, and an estimate for the Company’s liability for Incurred But Not Reported (“IBNR”) claims and for the ongoing development of existing claims. The reserves for IBNR claims and for the ongoing development of existing claims in each reporting period includes estimates. The Company has established reserves for workers’ compensation claims using loss development rates which are estimated using periodic third party actuarial valuations based upon historical loss statistics which include the Company’s historical frequency and severity of workers’ compensation claims, and an estimate of future cost trends. While management believes that its assumptions and estimates are appropriate, significant differences in actual experience or significant changes in assumptions may materially affect the Company’s future results.
Foreign Currency Translation	Foreign Currency Translation. The reporting currency of the Company and its subsidiaries is the U.S. dollar. The functional currency of the Company's foreign subsidiaries is their local currency. The results of operations of the Company’s foreign subsidiaries are translated at the monthly average exchange rates prevailing during the period. The financial position of the Company’s foreign subsidiaries is translated at the current exchange rates at the end of the period, and the related translation adjustments are recorded as a component of accumulated other comprehensive income within Stockholders’ Equity. Gains and losses resulting from foreign currency transactions are included as a component of selling, general and administrative expenses in the Consolidated Statements of Operations, and have not been material for all periods presented.
Stock-based Compensation	Stock-based Compensation . Under various stock plans, officers, employees and outside directors have received or may receive grants of restricted stock, stock units, stock appreciation rights or options to purchase common stock. The Company recognizes compensation expense equal to the grant-date fair value for all stock-based payment awards that are expected to vest. This expense is recorded on a straight-line basis over the requisite service period of the entire award, unless the awards are subject to performance conditions, in which case the Company recognizes compensation expense over the requisite service period of each separate vesting tranche. The Company determines the grant-date fair value of its restricted stock and stock unit awards using the fair market value of its stock on the grant date, unless the awards are subject to market conditions, in which case the Company utilizes a binomial-lattice model (i.e., Monte Carlo simulation model). The Monte Carlo simulation model utilizes multiple input variables to determine the stock-based compensation expense.
Property and Equipment	Property and Equipment . Property and equipment are recorded at cost. Depreciation expense is computed using the straight-line method over the following useful lives: Computer hardware 2 to 3 years Computer software 2 to 5 years Furniture and equipment 5 years Leasehold improvements Term of lease, 5 years maximum
Internal-use Software	Internal-use Software. The Company capitalizes direct costs incurred in the development of internal-use software. Amounts capitalized are reported as a component of computer software within property and equipment.
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted Accounting Pronouncements Stock Compensation. In March 2016, the Financial Accounting Standards Board (“FASB”) issued authoritative guidance which changes financial reporting as it relates to Employee Share-Based Payment Accounting. Under the new guidance, several aspects of the accounting for share-based payment award transactions will be simplified, including: i) income tax consequences; ii) classification of awards as either equity or liabilities; and iii) classification on the statement of cash flows. The new guidance was effective for annual and interim periods beginning after December 15, 2016 and was adopted by the Company effective January 1, 2017. The adoption of this guidance did not have a material impact on the Company’s financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted Revenue from Contracts with Customers. In May 2014, the FASB issued authoritative guidance that provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The new guidance requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. It also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. The amended guidance also requires additional quantitative and qualitative disclosures. In March 2016, amended guidance was issued to clarify implementation guidance on principal versus agent consideration. In April 2016 an amendment provided clarifications on determining whether a promised license provides a customer with a right to use or a right to access an entity’s intellectual property. In May 2016 an amendment provided narrow scope improvements and practical expedients to reduce the potential diversity, cost and complexity of applying new revenue standard. These amendments, as well as the original guidance, are all effective for annual and interim periods beginning after December 15, 2017. The new standard was adopted by the Company effective January 1, 2018. The standard is required to be adopted on either a full or modified retrospective basis. As the initial adoption of the standard did not have a material impact on the Company’s financial statements, prior periods will not be restated. The Company also had no significant changes to systems, processes, or controls. Lease Accounting. In February 2016, the FASB issued authoritative guidance which changes financial reporting as it relates to leasing transactions. Under the new guidance, lessees will be required to recognize a lease liability, measured on a discounted basis; and a right-of-use asset, for the lease term. The new guidance is effective for annual and interim periods beginning after December 15, 2018. Early application is permitted for all entities upon issuance. Lessees and lessors must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. While the impact of the adoption of this guidance will include the recognition of right-of-use assets and lease liabilities on the Company’s statement of financial position, the Company is in the process of evaluating the impact of adoption of this guidance on its systems, processes, and controls. Classification of Certain Cash Receipts and Cash Payments in Statement of Cash Flows. In August 2016, the FASB issued authoritative guidance designed to address diversity in how certain cash receipts and cash payments are presented and classified in the statement of cash flows, including: i) contingent consideration payments made after a business combination; ii) proceeds from the settlement of insurance claims; and iii) proceeds from the settlement of corporate-owned life insurance policies. The new guidance is effective for the Company for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted in any interim or annual period. The Company believes the adoption of this guidance will not have a material impact on its financial statements. Simplifying the Test for Goodwill Impairment. In January 2017, the FASB issued authoritative guidance to simplify the goodwill impairment testing process. The new standard eliminates Step 2 of the goodwill impairment test. If a company determines in Step 1 of the goodwill impairment test that the carrying value of goodwill is greater than the fair value, an impairment in that amount should be recorded to the income statement, rather than proceeding to Step 2. The new guidance is effective for the Company beginning after December 31, 2019, although early adoption is permitted. The Company believes the adoption of this guidance will not have a material impact on its financial statements. Stock Compensation. In May 2017, the FASB issued authoritative guidance updating which changes in the terms or conditions of a share-based payment award require an entity to apply modification accounting. Under the amended guidance, entities are required to account for the effects of a modification if the fair value, vesting conditions or classification (as an equity instrument or a liability instrument) of the modified award change from that of the original award immediately before the modification. The new guidance is effective for the Company in interim or annual periods beginning after December 15, 2017. The Company believes the adoption of this guidance will not have a material impact on its financial statements.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Advertising Costs	Advertising costs for the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Advertising Costs $ 49,433 $ 47,312 $ 44,015
Depreciation Expense Computed Using Straight-Line Method over Useful Lives	Depreciation expense is computed using the straight-line method over the following useful lives: Computer hardware 2 to 3 years Computer software 2 to 5 years Furniture and equipment 5 years Leasehold improvements Term of lease, 5 years maximum Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Computer hardware $ 171,515 $ 170,746 Computer software 376,761 374,490 Furniture and equipment 102,424 100,472 Leasehold improvements 148,764 133,541 Other 9,907 9,993 Property and equipment, cost 809,371 789,242 Accumulated depreciation (664,484 ) (627,733 ) Property and equipment, net $ 144,887 $ 161,509
Internal-Use Software Development Costs Capitalized	Internal-use software development costs capitalized for the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Internal-use software development costs $ 9,030 $ 33,753 $ 31,964

Other Current Assets (Tables)

Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Current Assets	Other current assets consisted of the following (in thousands): December 31, 2017 2016 Deposits in trusts for employee deferred compensation plans $ 292,326 $ 236,371 Other 112,385 84,434 Other current assets $ 404,711 $ 320,805

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Activity in Goodwill	The following table sets forth the activity in goodwill from December 31, 2015 , through December 31, 2017 (in thousands): Goodwill Temporary and consultant staffing Permanent placement staffing Risk consulting and internal audit services Total Balance as of December 31, 2015 $ 133,173 $ 26,251 $ 49,155 $ 208,579 Acquisitions 1,248 — 299 1,547 Foreign currency translation adjustments (546 ) (236 ) 449 (333 ) Balance as of December 31, 2016 $ 133,875 $ 26,015 $ 49,903 $ 209,793 Foreign currency translation adjustments 613 144 335 1,092 Balance as of December 31, 2017 $ 134,488 $ 26,159 $ 50,238 $ 210,885

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Depreciation expense is computed using the straight-line method over the following useful lives: Computer hardware 2 to 3 years Computer software 2 to 5 years Furniture and equipment 5 years Leasehold improvements Term of lease, 5 years maximum Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Computer hardware $ 171,515 $ 170,746 Computer software 376,761 374,490 Furniture and equipment 102,424 100,472 Leasehold improvements 148,764 133,541 Other 9,907 9,993 Property and equipment, cost 809,371 789,242 Accumulated depreciation (664,484 ) (627,733 ) Property and equipment, net $ 144,887 $ 161,509

Accrued Payroll and Benefit C30

Accrued Payroll and Benefit Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued Payroll and Benefit Costs	Accrued payroll and benefit costs consisted of the following (in thousands): December 31, 2017 2016 Payroll and benefits $ 256,804 $ 243,301 Employee deferred compensation plans 312,429 252,349 Workers’ compensation 17,092 19,361 Payroll taxes 26,574 24,037 Accrued payroll and benefit costs $ 612,899 $ 539,048
Employee Deferred Compensation Plans	Included in employee deferred compensation plans is the following (in thousands): December 31, 2017 2016 Deferred compensation plan and other benefits related to the Company’s Chief Executive Officer $ 86,145 $ 83,899

Notes Payable and Other Indeb31

Notes Payable and Other Indebtedness (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Maturities for Notes Payable and Other Indebtedness	The following table shows the schedule of maturities for notes payable and other indebtedness at December 31, 2017 (in thousands): 2018 $ 183 2019 200 2020 218 2021 239 2022 — $ 840

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision (Benefit) for Income Taxes	The provision (benefit) for income taxes for the years ended December 31, 2017 , 2016 and 2015 , consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Current: Federal $ 133,097 $ 156,937 $ 181,640 State 24,944 34,927 36,281 Foreign 27,079 20,725 13,892 Deferred: Federal and state 41,717 (3,785 ) (8,398 ) Foreign 95 1,917 (181 ) $ 226,932 $ 210,721 $ 223,234
Income Before Provision for Income Taxes	Income before the provision for income taxes for the years ended December 31, 2017 , 2016 and 2015 , consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Domestic $ 445,418 $ 494,890 $ 528,916 Foreign 72,098 59,220 52,114 $ 517,516 $ 554,110 $ 581,030
Difference of Income Taxes from Statutory Federal Income Tax Rates	The income taxes shown above varied from the statutory federal income tax rates for these periods as follows: Years Ended December 31, 2017 2016 2015 Federal U.S. income tax rate 35.0 % 35.0 % 35.0 % State income taxes, net of federal tax benefit 3.7 4.2 4.2 Non-deductible expenses 0.4 0.5 0.5 Non-U.S. income taxed at different rates, net of foreign tax credits — (0.6 ) 0.1 Federal tax credits (1.3 ) (0.8 ) (0.6 ) Tax impact of uncertain tax positions 0.2 — (0.2 ) Valuation allowance release, net — (0.1 ) (0.5 ) Tax effects of TCJA 6.5 — — Other, net (0.6 ) (0.2 ) (0.1 ) Effective tax rate 43.9 % 38.0 % 38.4 %
Deferred Portion of Tax Provision (Benefit)	The deferred portion of the tax provision (benefit) consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Amortization of franchise rights $ 495 $ 500 $ 514 Amortization of other intangibles 1,193 1,221 1,590 Accrued expenses, deducted for tax when paid 15,213 (6,889 ) (17,664 ) Capitalized costs for books, deducted for tax (5,790 ) 5,901 5,315 Depreciation (4,079 ) (2,405 ) (5,932 ) Federal impact of unrecognized tax benefits 39 75 1,058 Foreign tax credit carryforwards — — 3,636 Tax effects of TCJA 34,633 — — Other, net 108 (271 ) 2,904 $ 41,812 $ (1,868 ) $ (8,579 )
Components of Deferred Income Tax Amounts	The components of the deferred income tax amounts at December 31, 2017 and 2016 , were as follows (in thousands): December 31, 2017 2016 Deferred Income Tax Assets Provision for bad debts $ 6,794 $ 10,510 Deferred compensation and other benefit obligations 68,101 112,811 Workers’ compensation 3,127 5,634 Stock-based compensation 8,614 16,772 Credits and net operating loss carryforwards 30,087 30,534 Other 13,343 18,116 Total deferred income tax assets 130,066 194,377 Deferred Income Tax Liabilities Amortization of intangible assets (20,220 ) (28,681 ) Property and equipment basis differences (4,421 ) (16,640 ) Other (10,847 ) (11,658 ) Total deferred income tax liabilities (35,488 ) (56,979 ) Valuation allowance (20,178 ) (18,907 ) Total deferred income tax assets, net $ 74,400 $ 118,491
Reconciliation of Total Amounts of Gross Unrecognized Tax Benefits	The following table reconciles the total amounts of gross unrecognized tax benefits from January 1, 2015 to December 31, 2017 (in thousands): December 31, 2017 2016 2015 Balance at beginning of period $ 731 $ 814 $ 4,573 Gross increases—tax positions in prior years 1,503 92 — Gross decreases—tax positions in prior years (257 ) — (1,807 ) Gross increases—tax positions in current year 956 114 120 Settlements (40 ) — (520 ) Lapse of statute of limitations (7 ) (289 ) (1,552 ) Balance at end of period $ 2,886 $ 731 $ 814

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Minimum Rental Commitments Under Non-Cancelable Leases	The approximate minimum rental commitments for 2018 and thereafter under non-cancelable leases in effect at December 31, 2017 were as follows (in thousands): 2018 $ 85,484 2019 73,763 2020 64,221 2021 47,107 2022 35,535 Thereafter 64,042 $ 370,152

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Number and Cost of Common Stock Shares Repurchased	The number and the cost of common stock shares repurchased during the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Common stock repurchased (in shares) 4,046 4,046 4,343 Common stock repurchased $ 196,645 $ 163,614 $ 228,166
Number and Cost of Employee Stock Plan Repurchases	The number and the cost of employee stock plan repurchases made during the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Repurchases related to employee stock plans (in shares) 408 359 474 Repurchases related to employee stock plans $ 20,391 $ 15,170 $ 24,755
Cash Dividends Declared	The cash dividends declared during the years ended December 31, 2017 , 2016 and 2015 , are reflected in the following table: Years Ended December 31, 2017 2016 2015 Cash dividends declared per share $ .96 $ .88 $ .80

Stock Plans (Tables)

Stock Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Expense	Stock-based compensation expense consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Restricted stock and stock units - expense $ 42,191 $ 42,699 $ 41,292
Total Unrecognized Compensation Cost, Net of Estimated Forfeitures	Total unrecognized compensation cost, net of estimated forfeitures, consisted of the following (in thousands): December 31, 2017 2016 2015 Restricted stock and stock units - unrecognized future costs $ 62,730 $ 60,481 $ 60,627
Activity Under All Stock Plans and Weighted Average Exercise Prices	The following table reflects activity under all stock plans from December 31, 2014 through December 31, 2017 , and the weighted average exercise prices (in thousands, except per share amounts): Restricted Stock Plans without Market-Condition Restricted Stock Plans with Market-Condition Stock Option Plans Number of Shares/ Units Weighted Average Grant Date Fair Value Number of Shares/ Units Weighted Average Grant Date Fair Value Number of Shares/ Units Weighted Average Exercise Price Per Share Outstanding, December 31, 2014 1,165 $36.47 1,234 $40.24 77 $29.22 Granted 502 $58.14 257 $71.86 — — Exercised — — — — (54 ) $28.18 Restrictions lapsed (599 ) $36.30 (499 ) $31.41 — — Forfeited (16 ) $37.63 — — (11 ) $30.94 Outstanding, December 31, 2015 1,052 $46.88 992 $52.89 12 $32.36 Granted 772 $38.47 358 $45.93 — — Exercised — — — — (7 ) $32.36 Restrictions lapsed (545 ) $42.42 (364 ) $43.04 — — Forfeited (36 ) $41.28 (36 ) $43.04 (5 ) $32.36 Outstanding, December 31, 2016 1,243 $43.78 950 $54.42 — — Granted 904 $47.86 50 $50.09 — — Exercised — — — — — — Restrictions lapsed (616 ) $44.09 (384 ) $50.09 — — Forfeited (41 ) $43.68 — — — — Outstanding, December 31, 2017 1,490 $46.13 616 $56.76 — —
Pre-Tax Intrinsic Value of Stock Option Exercised	The total pre-tax intrinsic value of stock options exercised and the total fair value of shares vested during the years ended December 31, 2017 , 2016 and 2015, are reflected in the following table (in thousands): Years Ended December 31, 2017 2016 2015 Total pre-tax intrinsic value of stock options exercised $ — $ 52 $ 1,709 Total fair value of shares vested $ 50,385 $ 39,302 $ 56,570

Net Income Per Share (Tables)

Net Income Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Calculation of Net Income Per Share	The calculation of net income per share for the three years ended December 31, 2017 is reflected in the following table (in thousands, except per share amounts): Years Ended December 31, 2017 2016 2015 Net income $ 290,584 $ 343,389 $ 357,796 Basic: Weighted average shares 124,152 127,991 131,749 Diluted: Weighted average shares 124,152 127,991 131,749 Dilutive effect of potential common shares 740 775 1,181 Diluted weighted average shares 124,892 128,766 132,930 Net income per share: Basic $ 2.34 $ 2.68 $ 2.72 Diluted $ 2.33 $ 2.67 $ 2.69

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Reconciliation of Revenue and Operating Income by Reportable Segment to Consolidated Results	The following table provides a reconciliation of revenue and operating income by reportable segment to consolidated results (in thousands): Years Ended December 31, 2017 2016 2015 Net service revenues Temporary and consultant staffing $ 4,011,042 $ 4,026,777 $ 3,930,843 Permanent placement staffing 439,214 419,314 421,411 Risk consulting and internal audit services 816,533 804,308 742,679 $ 5,266,789 $ 5,250,399 $ 5,094,933 Operating income Temporary and consultant staffing $ 355,700 $ 393,704 $ 399,808 Permanent placement staffing 77,673 80,001 85,019 Risk consulting and internal audit services 83,907 80,754 95,845 517,280 554,459 580,672 Amortization of intangible assets 1,563 1,237 192 Interest income, net (1,799 ) (888 ) (550 ) Income before income taxes $ 517,516 $ 554,110 $ 581,030
Revenue and Long-Lived Assets by Geographic Location	The following tables represent revenues and long-lived assets by geographic location (in thousands): Years Ended December 31, 2017 2016 2015 Net service revenues (a) Domestic $ 4,121,701 $ 4,220,477 $ 4,105,013 Foreign (b) 1,145,088 1,029,922 989,920 $ 5,266,789 $ 5,250,399 $ 5,094,933 December 31, 2017 2016 2015 Assets, long-lived Domestic $ 113,069 $ 136,434 $ 117,176 Foreign 31,818 25,075 25,730 $ 144,887 $ 161,509 $ 142,906 (a) There were no customers that accounted for more than 10% of the Company’s total net revenue in any year presented. (b) No individual country represented more than 10% of revenues in any year presented.

Quarterly Financial Data (Una38

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	The following tabulation shows certain quarterly financial data for 2017 and 2016 (in thousands, except per share amounts): Quarter 2017 1 2 3 4 Net service revenues $ 1,287,370 $ 1,308,428 $ 1,324,709 $ 1,346,282 Gross margin $ 525,828 $ 538,438 $ 546,400 $ 553,146 Income before income taxes $ 125,501 $ 130,707 $ 132,270 $ 129,038 Net income $ 78,521 $ 80,316 $ 84,700 $ 47,047 Basic net income per share $ .63 $ .64 $ .69 $ .38 Diluted net income per share $ .62 $ .64 $ .68 $ .38 Quarter 2016 1 2 3 4 Net service revenues $ 1,302,625 $ 1,344,160 $ 1,338,541 $ 1,265,073 Gross margin $ 531,972 $ 556,993 $ 552,509 $ 519,202 Income before income taxes $ 133,791 $ 149,414 $ 146,324 $ 124,581 Net income $ 83,416 $ 91,616 $ 90,569 $ 77,788 Basic net income per share $ .65 $ .71 $ .71 $ .61 Diluted net income per share $ .64 $ .71 $ .71 $ .61

Subsequent Events (Tables)

Subsequent Events (Tables)	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	On February 13, 2018, the Company announced the following: Quarterly dividend per share $.28 Declaration date February 13, 2018 Record date February 23, 2018 Payment date March 15, 2018

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Accounting Policies [Abstract]
Number of reportable segments | segment	3
Advertising Costs	$ 49,433,000	$ 47,312,000	$ 44,015,000
Goodwill [Line Items]
Valuation allowance	20,178,000	$ 18,907,000
Provision for workers' compensation claims threshold	$ 500,000
Minimum
Goodwill [Line Items]
Amortized life assigned to identifiable intangible assets (in years)	2 years
Maximum
Goodwill [Line Items]
Amortized life assigned to identifiable intangible assets (in years)	5 years

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Property Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Computer hardware | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Computer hardware | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Computer software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Computer software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Internal Use Software (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Internal-use software development costs	$ 9,030	$ 33,753	$ 31,964

Other Current Assets (Details)

Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deposits in trusts for employee deferred compensation plans	$ 292,326	$ 236,371
Other	112,385	84,434
Other current assets	$ 404,711	$ 320,805

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 209,793	$ 208,579
Acquisitions		1,547
Foreign currency translation adjustments	1,092	(333)
Ending balance	210,885	209,793
Temporary and consultant staffing
Goodwill [Roll Forward]
Beginning balance	133,875	133,173
Acquisitions		1,248
Foreign currency translation adjustments	613	(546)
Ending balance	134,488	133,875
Permanent placement staffing
Goodwill [Roll Forward]
Beginning balance	26,015	26,251
Acquisitions		0
Foreign currency translation adjustments	144	(236)
Ending balance	26,159	26,015
Risk consulting and internal audit services
Goodwill [Roll Forward]
Beginning balance	49,903	49,155
Acquisitions		299
Foreign currency translation adjustments	335	449
Ending balance	$ 50,238	$ 49,903

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 809,371	$ 789,242
Accumulated depreciation	(664,484)	(627,733)
Property and equipment, net	144,887	161,509	$ 142,906
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, cost	171,515	170,746
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, cost	376,761	374,490
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost	102,424	100,472
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, cost	148,764	133,541
Other
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 9,907	$ 9,993

Accrued Payroll and Benefit C46

Accrued Payroll and Benefit Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Payroll and benefits	$ 256,804	$ 243,301
Employee deferred compensation plans	312,429	252,349
Workers’ compensation	17,092	19,361
Payroll taxes	26,574	24,037
Accrued payroll and benefit costs	612,899	539,048
Chief Executive Officer
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plan and other benefits related to the Company’s Chief Executive Officer	$ 86,145	$ 83,899

Notes Payable and Other Indeb47

Notes Payable and Other Indebtedness - Additional Information (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Promissory notes and other forms of indebtedness, issued	$ 800,000	$ 1,000,000
Weighted average interest rate	9.00%	9.00%	9.00%
Uncommitted letter of credit facility	$ 35,000,000
Debt support standby letters of credit	$ 17,400,000	$ 15,800,000
Service fee percentage	1.125%
Standby letter of credit
Debt Instrument [Line Items]
Promissory notes and other forms of indebtedness collateralized	$ 800,000
Standby letters of credit used for collateral requirements
Debt Instrument [Line Items]
Letters of credit outstanding	$ 16,600,000	$ 14,800,000

Notes Payable and Other Indeb48

Notes Payable and Other Indebtedness - Schedule of Maturities for Notes Payable and Other Indebtedness (Details) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 183
2,019	200
2,020	218
2,021	239
2,022	0
Notes payable and other indebtedness	$ 840

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 133,097	$ 156,937	$ 181,640
State	24,944	34,927	36,281
Foreign	27,079	20,725	13,892
Deferred:
Federal and state	41,717	(3,785)	(8,398)
Foreign	95	1,917	(181)
Provision (benefit) for income taxes	$ 226,932	$ 210,721	$ 223,234

Income Taxes - Income Before Pr

Income Taxes - Income Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic									$ 445,418	$ 494,890	$ 528,916
Foreign									72,098	59,220	52,114
Income before income taxes	$ 129,038	$ 132,270	$ 130,707	$ 125,501	$ 124,581	$ 146,324	$ 149,414	$ 133,791	$ 517,516	$ 554,110	$ 581,030

Income Taxes - Difference of In

Income Taxes - Difference of Income Taxes from Statutory Federal Income Tax Rates (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal U.S. income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	3.70%	4.20%	4.20%
Non-deductible expenses	0.40%	0.50%	0.50%
Non-U.S. income taxed at different rates, net of foreign tax credits	(0.00%)	(0.60%)	0.10%
Federal tax credits	(1.30%)	(0.80%)	(0.60%)
Tax impact of uncertain tax positions	0.20%	0.00%	(0.20%)
Valuation allowance release, net	0.00%	(0.10%)	(0.50%)
Tax effects of TCJA	6.50%	0.00%	0.00%
Other, net	(0.60%)	(0.20%)	(0.10%)
Effective tax rate	43.90%	38.00%	38.40%

Income Taxes - Deferred Portion

Income Taxes - Deferred Portion of Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Amortization of franchise rights	$ 495	$ 500	$ 514
Amortization of other intangibles	1,193	1,221	1,590
Accrued expenses, deducted for tax when paid	15,213	(6,889)	(17,664)
Capitalized costs for books, deducted for tax	(5,790)	5,901	5,315
Depreciation	(4,079)	(2,405)	(5,932)
Federal impact of unrecognized tax benefits	39	75	1,058
Foreign tax credit carryforwards	0	0	3,636
Tax effects of TCJA	34,633	0	0
Other, net	108	(271)	2,904
Deferred Portion Of Tax Expense Benefit, Total	$ 41,812	$ (1,868)	$ (8,579)

Income Taxes - Components of De

Income Taxes - Components of Deferred Income Tax Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Income Tax Assets
Provision for bad debts	$ 6,794	$ 10,510
Deferred compensation and other benefit obligations	68,101	112,811
Workers’ compensation	3,127	5,634
Stock-based compensation	8,614	16,772
Credits and net operating loss carryforwards	30,087	30,534
Other	13,343	18,116
Total deferred income tax assets	130,066	194,377
Deferred Income Tax Liabilities
Amortization of intangible assets	(20,220)	(28,681)
Property and equipment basis differences	(4,421)	(16,640)
Other	(10,847)	(11,658)
Total deferred income tax liabilities	(35,488)	(56,979)
Valuation allowance	(20,178)	(18,907)
Total deferred income tax assets, net	$ 74,400	$ 118,491

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Provisional estimate recorded related to re-measurement of deferred tax balance	$ 34,600
Provisional amount recorded in connection with the transition tax offset by foreign tax credits	7,700
Amount expected to be utilized of tax credit carry forwards expiring in the and beyond the stated year	2,000
Valuation allowance	20,178	$ 18,907
Unrecognized tax benefits, impact on effective tax rate	2,800	500	$ 500
Accrued interest and penalties	100	100	200
Increase (decrease) in income tax expense		$ (100)	$ (2,300)
Unrecognized tax benefits, gross	100
Foreign Countries
Income Taxes [Line Items]
Valuation allowance	18,700
Foreign Countries
Income Taxes [Line Items]
Net operating loss carryforwards, foreign	26,400
California enterprise zone
Income Taxes [Line Items]
California enterprise zone tax credits	3,500
California enterprise zone | California Enterprise Zone
Income Taxes [Line Items]
Valuation allowance	$ 1,500

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Total Amounts of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 731	$ 814	$ 4,573
Gross increases—tax positions in prior years	1,503	92	0
Gross decreases—tax positions in prior years	(257)	0	(1,807)
Gross increases—tax positions in current year	956	114	120
Settlements	(40)	0	(520)
Lapse of statute of limitations	(7)	(289)	(1,552)
Balance at end of period	$ 2,886	$ 731	$ 814

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rental expense	$ 87,500,000	$ 87,300,000	$ 85,900,000
Rodriguez Case
Loss Contingencies [Line Items]
Allegations loss	0
Gentry Case
Loss Contingencies [Line Items]
Allegations loss	$ 0

Commitments and Contingencies57

Commitments and Contingencies - Minimum Rental Commitments Under Non-Cancelable Leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 85,484
2,019	73,763
2,020	64,221
2,021	47,107
2,022	35,535
Thereafter	64,042
Operating Leases, Future Minimum Payments Due, Total	$ 370,152

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) shares in Millions	Dec. 31, 2017shares
Equity [Abstract]
Shares remaining under existing repurchase program	2.3

Stockholders' Equity - Number o

Stockholders' Equity - Number of Cost of Common Stock Shares Repurchased (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Common stock repurchased (in shares)	4,046	4,046	4,343
Common stock repurchased	$ 196,645	$ 163,614	$ 228,166

Stockholders' Equity - Number a

Stockholders' Equity - Number and Cost of Employee Stock Plan Repurchases (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Repurchases related to employee stock plans (in shares)	408	359	474
Repurchases related to employee stock plans	$ 20,391	$ 15,170	$ 24,755

Stockholders' Equity - Cash Div

Stockholders' Equity - Cash Dividends Declared (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Cash dividends declared per share (in USD per share)	$ 0.96	$ 0.88	$ 0.8

Stock Plans - Additional Inform

Stock Plans - Additional Information (Details) shares in Millions	12 Months Ended
	Dec. 31, 2017shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for grants (in years)	3 years
Unrecognized compensation cost expected to be recognized over the period (years)	4 years
Total number of available shares to grant	3.8
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual shares earned, possible percentage on target award	75.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual shares earned, possible percentage on target award	125.00%
Restricted stock and stock units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for grants (in years)	3 years
Restricted stock and stock units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for grants (in years)	4 years

Stock Plans - Stock-Based Compe

Stock Plans - Stock-Based Compensation Expense (Details) - Restricted stock and stock units - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 42,191	$ 42,699	$ 41,292
Total unrecognized compensation cost, net of estimated forfeitures	$ 62,730	$ 60,481	$ 60,627

Stock Plans - Activity Under Al

Stock Plans - Activity Under All Stock Plans and Weighted Average Exercise Prices (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options, Number of Shares/Units:
Outstanding Beginning Balance (in shares)	0	12	77
Granted (in shares)	0	0	0
Exercised (in shares)	0	(7)	(54)
Restrictions lapsed (in shares)	0	0	0
Forfeited (in shares)	0	(5)	(11)
Outstanding, Ending Balance (in shares)	0	0	12
Weighted Average Exercise Price Per Share:
Outstanding Beginning Balance (usd per share)	$ 0	$ 32.36	$ 29.22
Granted (usd per share)	0	0	0
Exercised (usd per share)	0	32.36	28.18
Restrictions lapsed (usd per share)	0	0	0
Forfeited (usd per share)	0	32.36	30.94
Outstanding Ending Balance (usd per share)	$ 0	$ 0	$ 32.36
Restricted stock and stock units | Restricted Stock Plans without Market-Condition
Number of Shares/Units:
Number of Shares/Units, Outstanding Beginning Balance (in shares)	1,243	1,052	1,165
Granted (in shares)	904	772	502
Exercised (in shares)	0	0	0
Restrictions lapsed (in shares)	(616)	(545)	(599)
Forfeited (in shares)	(41)	(36)	(16)
Outstanding, Ending Balance (in shares)	1,490	1,243	1,052
Weighted Average Grant Date Fair Value:
Outstanding Beginning Balance (usd per share)	$ 43.78	$ 46.88	$ 36.47
Granted (usd per share)	47.86	38.47	58.14
Exercised (usd per share)	0	0	0
Restrictions lapsed (usd per share)	44.09	42.42	36.30
Forfeited (usd per share)	43.68	41.28	37.63
Outstanding Ending Balance (usd per share)	$ 46.13	$ 43.78	$ 46.88
Restricted stock and stock units | Restricted Stock Plans with Market-Condition
Number of Shares/Units:
Number of Shares/Units, Outstanding Beginning Balance (in shares)	950	992	1,234
Granted (in shares)	50	358	257
Exercised (in shares)	0	0	0
Restrictions lapsed (in shares)	(384)	(364)	(499)
Forfeited (in shares)	0	(36)	0
Outstanding, Ending Balance (in shares)	616	950	992
Weighted Average Grant Date Fair Value:
Outstanding Beginning Balance (usd per share)	$ 54.42	$ 52.89	$ 40.24
Granted (usd per share)	50.09	45.93	71.86
Exercised (usd per share)	0	0	0
Restrictions lapsed (usd per share)	50.09	43.04	31.41
Forfeited (usd per share)	0	43.04	0
Outstanding Ending Balance (usd per share)	$ 56.76	$ 54.42	$ 52.89

Stock Plans - Total Pre-Tax Int

Stock Plans - Total Pre-Tax Intrinsic Value of Stock Options Exercised and Total Fair Value of Shares Vested (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total pre-tax intrinsic value of stock options exercised	$ 0	$ 52	$ 1,709
Total fair value of shares vested	$ 50,385	$ 39,302	$ 56,570

Net Income Per Share - Calculat

Net Income Per Share - Calculation of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 47,047	$ 84,700	$ 80,316	$ 78,521	$ 77,788	$ 90,569	$ 91,616	$ 83,416	$ 290,584	$ 343,389	$ 357,796
Basic:
Weighted average shares (in shares)									124,152	127,991	131,749
Diluted:
Weighted average shares (in shares)									124,152	127,991	131,749
Dilutive effect of potential common shares (in shares)									740	775	1,181
Diluted weighted average shares (in shares)									124,892	128,766	132,930
Net income per share:
Basic (usd per share)	$ 0.38	$ 0.69	$ 0.64	$ 0.63	$ 0.61	$ 0.71	$ 0.71	$ 0.65	$ 2.34	$ 2.68	$ 2.72
Diluted (usd per share)	$ 0.38	$ 0.68	$ 0.64	$ 0.62	$ 0.61	$ 0.71	$ 0.71	$ 0.64	$ 2.33	$ 2.67	$ 2.69

Business Segments - Additional

Business Segments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017segment
Segment Reporting [Abstract]
Number of reportable segments	3

Business Segments - Reconciliat

Business Segments - Reconciliation of Revenue and Operating Income by Reportable Segment to Consolidated Results (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net service revenues	$ 1,346,282	$ 1,324,709	$ 1,308,428	$ 1,287,370	$ 1,265,073	$ 1,338,541	$ 1,344,160	$ 1,302,625	$ 5,266,789	$ 5,250,399	$ 5,094,933
Amortization of intangible assets									1,563	1,237	192
Interest income, net									(1,799)	(888)	(550)
Income before income taxes	$ 129,038	$ 132,270	$ 130,707	$ 125,501	$ 124,581	$ 146,324	$ 149,414	$ 133,791	517,516	554,110	581,030
Operating segments
Segment Reporting Information [Line Items]
Net service revenues									5,266,789	5,250,399	5,094,933
Operating income									517,280	554,459	580,672
Operating segments | Temporary and consultant staffing
Segment Reporting Information [Line Items]
Net service revenues									4,011,042	4,026,777	3,930,843
Operating income									355,700	393,704	399,808
Operating segments | Permanent placement staffing
Segment Reporting Information [Line Items]
Net service revenues									439,214	419,314	421,411
Operating income									77,673	80,001	85,019
Operating segments | Risk consulting and internal audit services
Segment Reporting Information [Line Items]
Net service revenues									816,533	804,308	742,679
Operating income									83,907	80,754	95,845
Segment reconciling items
Segment Reporting Information [Line Items]
Amortization of intangible assets									1,563	1,237	192
Interest income, net									$ (1,799)	$ (888)	$ (550)

Business Segments - Revenue and

Business Segments - Revenue and Long-Lived Assets by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net service revenues	$ 1,346,282	$ 1,324,709	$ 1,308,428	$ 1,287,370	$ 1,265,073	$ 1,338,541	$ 1,344,160	$ 1,302,625	$ 5,266,789	$ 5,250,399	$ 5,094,933
Assets, long-lived	144,887				161,509				144,887	161,509	142,906
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Net service revenues									4,121,701	4,220,477	4,105,013
Assets, long-lived	113,069				136,434				113,069	136,434	117,176
Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Net service revenues									1,145,088	1,029,922	989,920
Assets, long-lived	$ 31,818				$ 25,075				$ 31,818	$ 25,075	$ 25,730

Quarterly Financial Data (Una70

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net service revenues	$ 1,346,282	$ 1,324,709	$ 1,308,428	$ 1,287,370	$ 1,265,073	$ 1,338,541	$ 1,344,160	$ 1,302,625	$ 5,266,789	$ 5,250,399	$ 5,094,933
Gross margin	553,146	546,400	538,438	525,828	519,202	552,509	556,993	531,972	2,163,812	2,160,676	2,114,471
Income before income taxes	129,038	132,270	130,707	125,501	124,581	146,324	149,414	133,791	517,516	554,110	581,030
Net income	$ 47,047	$ 84,700	$ 80,316	$ 78,521	$ 77,788	$ 90,569	$ 91,616	$ 83,416	$ 290,584	$ 343,389	$ 357,796
Basic net income per share (in USD per share)	$ 0.38	$ 0.69	$ 0.64	$ 0.63	$ 0.61	$ 0.71	$ 0.71	$ 0.65	$ 2.34	$ 2.68	$ 2.72
Diluted net income per share (in USD per share)	$ 0.38	$ 0.68	$ 0.64	$ 0.62	$ 0.61	$ 0.71	$ 0.71	$ 0.64	$ 2.33	$ 2.67	$ 2.69

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Feb. 13, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Shares remaining under existing repurchase program		2,300,000
Subsequent Event
Subsequent Event [Line Items]
Additional number of shares authorized to be repurchased	10,000,000
Quarterly dividend per share	$ 0.28
Declaration date	Feb. 13, 2018
Record date	Feb. 23, 2018
Payment date	Mar. 15, 2018

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 33,133	$ 35,087	$ 30,544
Charged to Expenses	8,022	9,192	12,005
Deductions	(8,751)	(9,907)	(5,353)
Translation Adjustments	777	(1,239)	(2,109)
Balance at End of Period	33,181	33,133	35,087
Deferred tax valuation allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	18,907	26,329	29,561
Charged to Expenses	1,411	2,160	6,283
Deductions	(1,275)	(9,517)	(8,068)
Translation Adjustments	1,135	(65)	(1,447)
Balance at End of Period	$ 20,178	$ 18,907	$ 26,329