Description of Business and Significant Accounting Policies	12 Months Ended
Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Significant Accounting Policies	DESCRIPTION OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES Description of Business TriNet Group, Inc. (the Company or TriNet), a Delaware corporation incorporated in January 2000, provides comprehensive human resources, or HR, solutions for small to midsize businesses, or SMBs, across a number of industries under a co-employment model. The Company’s HR solutions are designed to manage an increasingly complex set of HR regulations, costs, risks and responsibilities for its clients, allowing them to focus on operating and growing their core businesses. These HR solutions include bundled services, such as multi-state payroll processing and tax administration, employee benefits programs, including health insurance and retirement plans, workers compensation insurance and claims management, federal, state and local labor, employment and benefit law compliance, risk mitigation, expense and time management, human capital consulting and other services. The Company provides its services through co-employment relationships with its clients, under which the Company and its clients each take responsibility for certain portions of the employer-employee relationship for worksite employees (WSEs). The Company is the employer of record for most administrative and regulatory purposes, including the following: (i) compensation through wages and salaries; (ii) employer payroll-related taxes payment; (iii) employee payroll-related taxes withholding and payment; (iv) employee benefit programs including health and life insurance, and others; and (v) workers compensation coverage. The client is responsible for responsibilities not assumed by the Company, including the day-to-day job responsibilities of the WSEs. Segment Information The Company operates in one reportable segment in accordance with Accounting Standard Codification (ASC) 280 – Segment Reporting, issued by the Financial Accounting Standards Board (FASB). All of the Company’s service revenues are generated from external clients. Less than 1% of revenue is generated outside of the United States of America (U.S.). Substantially all of the Company’s long-lived assets are located in the U.S. Basis of Presentation The accompanying consolidated financial statements and footnotes thereto of the Company and its wholly owned subsidiaries have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). All intercompany accounts and transactions have been eliminated in consolidation. Certain prior period amounts in the consolidated balance sheets, the consolidated statement of stockholders’equity (deficit), the consolidated statement of cash flows and Note 3 have been reclassified to conform to the current presentation. The accompanying consolidated balance sheets present the current assets and current liabilities directly related to the processing of human resources transactions as WSE-related assets and WSE-related liabilities, respectively. WSE-related assets consist of cash and investments restricted for current workers compensation claim payments, payroll funds collected, accounts receivable, unbilled service revenues, and refundable or prepaid amounts related to the Company-sponsored workers compensation and health plan programs. WSE-related liabilities consist of client prepayments, wages and payroll taxes accrued and payable, and liabilities related to the Company-sponsored workers compensation and health plan programs resulting from workers compensation case reserves, premium amounts due to providers for enrolled employees, and workers compensation and health reserves that are expected to be disbursed within the next 12 months. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect certain reported amounts and disclosures. These estimates include, but are not limited to, allowances for accounts receivable, workers compensation-related assets and liabilities, health plan assets and liabilities, recoverability of goodwill and other intangible assets, income taxes, stock-based compensation and other contingent liabilities. Such estimates are based on historical experience and on various other assumptions that Company management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Revenue Recognition Professional service revenues represent fees charged to clients for processing HR transactions on behalf of the Company’s clients, such as payroll payments and remitting employment tax withholding amounts, providing access to the Company’s HR expertise, including HR templates, best practices, and interactions with our HR professionals, providing labor, employment and benefit law compliance services to assist clients in avoiding or reducing liability and exposure and providing additional services, including recruiting or other services, to support various stages of clients’ growth. Professional service revenues are recognized in the period the services are rendered and earned under service arrangements with clients where service fees are fixed or determinable and collectability is reasonably assured. Insurance service revenues consist of insurance-related billings and administrative fees collected from clients and withheld from WSEs for Company-sponsored, risk-based, fully-insured insurance plans provided through third-party insurance carriers, primarily employee health benefit insurance and workers compensation insurance. Insurance service revenues are recognized in the period amounts are due and collectability is reasonably assured. The professional service revenues and insurance service revenues are each considered separate units of accounting and the associated fees and insurance premiums are billed as such for the majority of the Company’s clients. For clients billed through a bundled invoice, the selling price of significant deliverables is determined based on the best estimate of the selling price. The Company is not the primary obligor for payroll and payroll tax payments and, therefore, these payments are not reflected as either revenue or expense. The gross payroll and payroll tax payments made on behalf of the clients, combined, were $30.6 billion, $25.6 billion and $17.6 billion for the years ended December 31, 2015, 2014, and 2013, respectively. The Company records a liability relating to work performed by WSEs but unpaid at the end of each period in the period in which the WSEs perform work, along with the related receivable for the same period. The Company generally charges an upfront non-refundable set-up fee for which the performance of onboarding services is not a discrete earnings event, and therefore the revenue is recognized on a straight-line basis over the estimated average client tenure. Insurance Costs Insurance premiums paid to the insurance carriers for the insurance coverage for clients and WSEs and the reimbursements paid to the insurance carriers or third-party administrators for claims payments made on the Company’s behalf within its insurance deductible layer, where applicable, are included in cost and operating expenses as insurance costs. Workers Compensation Insurance Reserves Workers compensation insurance reserves are established to provide for the estimated ultimate costs of paying claims within the deductible layer in accordance with workers compensation insurance policies. These reserves include estimates for reported losses, plus amounts for those claims incurred but not paid, and estimates of certain expenses associated with processing and settling the claims. In establishing the workers compensation insurance reserves, the Company uses an independent actuarial estimate of undiscounted future cash payments that would be made to settle the claims. In the Company's experience, plan years related to workers compensation programs may take up to 10 years or more to be settled. In estimating these reserves, the Company utilizes historical loss experience, exposure data, and actuarial judgment, together with a range of inputs which are primarily based upon the WSE job responsibilities, their location, the historical frequency and severity of workers compensation claims, and an estimate of future cost trends. All of these components could materially impact the reserves as reported in the consolidated financial statements. For each reporting period, changes in the actuarial assumptions resulting from changes in actual claims experience and other trends are incorporated into the workers compensation claims cost estimates. Accordingly, final claim settlements may vary materially from the present estimates, particularly when those payments may not occur until well into the future. The Company regularly reviews the adequacy of workers compensation insurance reserves. Adjustments to previously established reserves are reflected in the results of operations for the period in which the adjustment is identified. Such adjustments could be significant, reflecting any variety of new and adverse or favorable trends. Any unexpected increases in the severity or frequency of claims could result in material adverse effects to the operating results. The Company does not discount loss reserves accrued under these programs. Claim costs expected to be paid within one year are recorded as accrued workers compensation costs and included in short-term worksite employee related liabilities or short term worksite related assets if funds are held by third parties to cover the claims, while costs expected to be paid beyond one year are included in long-term liabilities or long term workers compensation receivables if funds are held by third parties to cover the claims on the consolidated balance sheets. Assets held by third parties to cover claim liabilities remain restricted until the plan year to which they relate are settled. At policy inception, annual premiums are estimated based on projected wages over the duration of the policy period. As actual wages are realized, the amounts paid for premiums may differ from the estimates recorded by the Company, creating an asset or liability throughout the policy year. Such differences could have a material effect on the Company’s consolidated financial position and results of operations. Health Benefits Health benefits insurance reserves are established to provide for the estimated costs of reimbursing the carriers for paying claims within the deductible layer in accordance with health insurance policies. These reserves include estimates for reported losses, plus estimates for claims incurred but not reported. Reserves are determined regularly by the Company based upon a number of factors, including but not limited to actuarial calculations, current and historical claims payment patterns, plan enrollment and medical trend rates. Ultimate health insurance reserves may vary in subsequent years from the amounts estimated. As of December 31, 2015 and 2014, liability reserves of $113.2 million and $82.1 million, respectively, were recorded within health benefits payable and are included in WSE-related liabilities in the accompanying consolidated balance sheets. Under certain contracts, based on plan performance, the Company may be entitled to receive refunds of premiums. We estimate these refunds based on premium and claims data and record these within prepaid health plan expenses and are included in WSE-related assets on the consolidated balance sheet. As of December 31, 2015 and 2014, the Company had $6.8 million and $4.9 million, respectively, as prepaid health plan expenses included within WSE-related assets. Cash and Cash Equivalents Cash and cash equivalents include bank deposits and short-term, highly liquid investments. Investments with original maturity dates of three months or less are considered cash equivalents. Investments The Company classifies its investments as available-for-sale and are carried at fair value. Unrealized gains and losses are reported as a component of accumulated other comprehensive income. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts from the date of purchase to maturity or sale. Such amortization is included in interest income as an addition to or deduction from the coupon interest earned on the investments. The Company uses the specific identification method of determining the cost basis in computing realized gains and losses on the sale of its available-for-sale securities. Realized gains and losses are included in other income in the accompanying consolidated statement of operations. The Company assesses whether an other-than-temporary impairment loss has occurred due to declines in fair value or other market conditions. With respect to debt securities, this assessment takes into account our current intent to sell, or not sell, the security, and whether it is more likely than not that we will not be required to sell the security before recovery of its amortized cost. Accounts Receivable The Company’s accounts receivable, which represent outstanding gross billings to clients, are reported net of an allowance for doubtful accounts. The Company establishes an allowance for doubtful accounts based on historical experience, the age of the accounts receivable balances, credit quality of clients, current economic conditions and other factors that may affect clients’ ability to pay, and charges off amounts when they are deemed uncollectible. Property and Equipment The Company records property and equipment at historical cost and computes depreciation using the straight-line method over the estimated useful lives of the assets or the lease terms, generally three to five years for software and office equipment, five to seven years for furniture and fixtures, and the shorter of the asset life or the remaining lease term for leasehold improvements. The Company expenses the cost of maintenance and repairs as incurred and capitalizes betterments. Internal Use Software The Company capitalizes internal and external costs incurred to develop internal-use computer software during the application development stage. Application development stage costs include license fees paid to third-parties for software use, software configuration, coding, and installation. Capitalized costs are amortized on a straight-line basis over the estimated useful life, typically ranging from three to five years, commencing when the software is placed into service. The Company expenses costs incurred during the preliminary project stage, as well as general and administrative, overhead, maintenance and training costs, and costs that do not add functionality to existing systems. For the years ended December 31, 2015, 2014 and 2013, internally developed software costs capitalized were $11.2 million, $6.3 million and $3.3 million respectively. Goodwill and Other Intangible Assets The Company’s goodwill and identifiable intangible assets with indefinite useful lives are not amortized, but instead are tested for impairment on an annual basis or when an event occurs or circumstances change in a way to indicate that there has been a potential decline in the fair value of the reporting unit. Impairment is determined by comparing the estimated fair value of the reporting unit to its carrying amount, including goodwill. The Company’s business is largely homogeneous and, as a result, all goodwill is associated with the Company’s one reportable segment. Intangible assets with finite useful lives include purchased client lists, trade names, developed technologies, and contractual agreements. Intangible assets are amortized over their respective estimated useful lives ranging from two to six years using either the straight-line method or an accelerated method. Intangible assets are reviewed for indicators of impairment at least annually and evaluated for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Based on the results of the Company’s reviews, no impairment loss was recognized in the results of operations for the years ended December 31, 2015, 2014 and 2013. Annually, the Company performs a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit has declined below carrying value. This assessment considers various financial, macroeconomic, industry, and reporting unit specific qualitative factors. The Company performs its annual impairment testing in its fiscal fourth quarter. Based on the results of the Company’s reviews, no impairment loss was recognized in the results of operations for the years ended December 31, 2015, 2014 and 2013. Impairment of Long-Lived Assets The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. An asset is considered impaired if the carrying amount exceeds the undiscounted future net cash flows the asset is expected to generate. An impairment charge is recognized for the amount by which the carrying amount of the assets exceeds its fair value. Assets to be disposed of are reported at the lower of the carrying amount or fair value, less selling costs. Advertising Costs The Company expenses the costs of producing advertisements at the time production occurs, and expenses the cost of running advertisements in the period in which the advertising space or airtime is used as sales and marketing expense. Advertising costs were $8.2 million, $7.3 million, and $7.5 million for the years ended December 31, 2015, 2014 and 2013, respectively. Stock-Based Compensation The Company has issued three types of stock-based awards to employees: restricted stock units, stock options and employee stock purchase plan. Compensation expense associated with restricted stock units is based on the fair value of common stock on the date of grant. Compensation expense associated with stock options and employee stock purchase plan are based on the estimated grant date fair value method using the Black-Scholes valuation model. Expense is recognized using a straight-line amortization method over the respective vesting period for awards that are ultimately expected to vest. Accordingly, stock-based compensation has been reduced for estimated forfeitures. When estimating forfeitures, the Company considers voluntary termination behaviors as well as trends of actual option forfeitures. A tax benefit from stock-based compensation is recognized in equity to the extent that an incremental tax benefit is realized. Income Taxes The Company recognizes deferred tax assets and liabilities for estimated future tax effects based on differences between the carrying amounts of assets and liabilities for financial reporting purposes and amounts used for income tax purposes under current tax laws. Deferred tax expense results from the change in the net liability for deferred income taxes between periods. The Company maintains a reserve for uncertain tax positions. The Company evaluates tax positions taken or expected to be taken in a tax return for recognition in its consolidated financial statements. Prior to recording the related tax benefit in the consolidated financial statements, the Company must conclude that tax positions are more likely than not to be sustained, assuming those positions will be examined by taxing authorities with full knowledge of all relevant information. The benefit recognized in the consolidated financial statements is the amount the Company expects to realize after examination by taxing authorities. If a tax position drops below the more likely than not standard, the benefit can no longer be recognized. Assumptions, judgment and the use of estimates are required in determining if the more likely than not standard has been met when developing the provision for income taxes and in determining the expected benefit. A change in the assessment of the more likely than not standard could materially impact the Company’s results of operations or financial position. The Company recognizes interest and penalties related to uncertain tax positions as a component of income tax expense. Concentrations of Credit Risk Financial instruments that subject the Company to concentrations of credit risk include cash and cash equivalents, investments, restricted cash and restricted investments (including payroll funds collected), accounts receivable, and amounts due from insurance carriers. The Company maintains its cash and cash equivalents, investments, restricted cash and restricted investments (including payroll funds collected) principally in domestic financial institutions and performs periodic evaluations of the relative credit standing of these institutions. The Company’s exposure to credit risk in the event of default by the financial institutions holding these funds is limited to amounts currently held by the institution in excess of insured amounts. Under the terms of professional services agreements, clients agree to maintain sufficient funds or other satisfactory credit at all times to cover the cost of its current payroll, all accrued paid time off, vacation or sick leave balances, and other vested wage and benefit obligations for all their work site employees. The Company generally requires payment from its clients on or before the applicable payroll date. For certain clients, the Company requires an indemnity guarantee payment (IGP) supported by a letter of credit, bond, or a certificate of deposit from certain financial institutions. The IGP typically equals the total payroll and service fee for one average payroll period. As of December 31, 2015 and December 31, 2014, one client accounted for 12% of accounts receivable. No client accounted for more than 10% of total revenues in the years ended December 31, 2015, 2014 and 2013. Bad debt expense, net of recoveries was $2.0 million, $1.4 million and $0.6 million for the years ended December 31, 2015, 2014 and 2013, respectively. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or (FASB), issued Accounting Standards Update (ASU) 2016-02—Leases. The amendment requires that lease arrangements longer than 12 months result in an entity recognizing an asset and liability. The amendment is effective for annual reporting periods, and interim periods within those years beginning after December 15, 2018. Early adoption is permitted. The Company is currently in the process of evaluating the impact of the adoption of this standard on its consolidated financial statements. In January 2016, the FASB issued ASU 2016-01—Recognition and Measurement of Financial Assets and Financial Liabilities. The amendment addresses various aspects of the recognition, measurement, presentation, and disclosure for financial instruments. The amendment is effective for annual reporting periods, and interim periods within those years beginning after December 15, 2017. Early adoption by public entities is permitted only for certain provisions. The Company is currently in the process of evaluating the impact of the adoption of this standard on its consolidated financial statements. In November 2015, the FASB issued ASU 2015-17—Balance Sheet Classification of Deferred Taxes, as part of its initiative to reduce complexity in accounting standards (the Simplification Initiative). The amendment requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early adoption is permitted. The Company adopted this guidance in 2015 with retrospective application. See Note 11 for further details. In April 2015, the FASB issued ASU 2015-05—Intangibles—Goodwill and Other—Internal-Use Software, as part of the Simplification Initiative. The amendment provides guidance to clarify the customer’s accounting for fees paid in a cloud computing arrangement. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. The Company expects to adopt this guidance in 2016. The Company does not expect this guidance to have a material effect on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-03—Interest—Imputation of Interest, as part of its Simplification Initiative. The amendment requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The Company expects to adopt this guidance in 2016. The Company does not expect this guidance to have a material effect on its consolidated financial statements. In August 2014, the FASB issued ASU 2014-15—Presentation of Financial Statements—Going Concern (Subtopic 205-40), which addresses management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. Management’s evaluation should be based on relevant conditions and events that are known and reasonably knowable at the date that the financial statements are issued. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company does not expect to adopt this guidance early and does not believe that the adoption of this guidance will have a material effect on its consolidated financial statements. In June 2014, the FASB issued ASU 2014-12—Compensation—Stock Compensation, which requires that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. ASU 2014-12 is effective for annual reporting periods, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted. The amendments may be applied prospectively to all awards granted or modified after the effective date or retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented. The Company does not expect this guidance to have a material effect on its consolidated financial statements. The Company expects to adopt this guidance in 2016. In May 2014, the FASB issued ASU 2014-09—Revenue from Contracts with Customers, which will replace most existing revenue recognition guidance under GAAP. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard provides a five-step analysis of transactions to determine when and how revenue is recognized. In July 2015, the FASB deferred the effective date to annual reporting periods, and interim periods within those years, beginning after December 15, 2017. Early adoption at the original effective date of December 15, 2016 is permitted. The amendments may be applied retrospectively or as a cumulative-effect adjustment as of the date of adoption. The Company has not yet selected a method of adoption and is currently evaluating the effect that the amendments will have on the consolidated financial statements.

DESCRIPTION OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES

Description of Business

TriNet Group, Inc. (the Company or TriNet), a Delaware corporation incorporated in January 2000, provides comprehensive human resources, or HR, solutions for small to midsize businesses, or SMBs, across a number of industries under a co-employment model. The Company’s HR solutions are designed to manage an increasingly complex set of HR regulations, costs, risks and responsibilities for its clients, allowing them to focus on operating and growing their core businesses. These HR solutions include bundled services, such as multi-state payroll processing and tax administration, employee benefits programs, including health insurance and retirement plans, workers compensation insurance and claims management, federal, state and local labor, employment and benefit law compliance, risk mitigation, expense and time management, human capital consulting and other services.

The Company provides its services through co-employment relationships with its clients, under which the Company and its clients each take responsibility for certain portions of the employer-employee relationship for worksite employees (WSEs). The Company is the employer of record for most administrative and regulatory purposes, including the following: (i) compensation through wages and salaries; (ii) employer payroll-related taxes payment; (iii) employee payroll-related taxes withholding and payment; (iv) employee benefit programs including health and life insurance, and others; and (v) workers compensation coverage. The client is responsible for responsibilities not assumed by the Company, including the day-to-day job responsibilities of the WSEs.

Segment Information

The Company operates in one reportable segment in accordance with Accounting Standard Codification (ASC) 280 – Segment Reporting, issued by the Financial Accounting Standards Board (FASB). All of the Company’s service revenues are generated from external clients. Less than 1% of revenue is generated outside of the United States of America (U.S.). Substantially all of the Company’s long-lived assets are located in the U.S.

Basis of Presentation

The accompanying consolidated financial statements and footnotes thereto of the Company and its wholly owned subsidiaries have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). All intercompany accounts and transactions have been eliminated in consolidation. Certain prior period amounts in the consolidated balance sheets, the consolidated statement of stockholders’equity (deficit), the consolidated statement of cash flows and Note 3 have been reclassified to conform to the current presentation.

The accompanying consolidated balance sheets present the current assets and current liabilities directly related to the processing of human resources transactions as WSE-related assets and WSE-related liabilities, respectively. WSE-related assets consist of cash and investments restricted for current workers compensation claim payments, payroll funds collected, accounts receivable, unbilled service revenues, and refundable or prepaid amounts related to the Company-sponsored workers compensation and health plan programs. WSE-related liabilities consist of client prepayments, wages and payroll taxes accrued and payable, and liabilities related to the Company-sponsored workers compensation and health plan programs resulting from workers compensation case reserves, premium amounts due to providers for enrolled employees, and workers compensation and health reserves that are expected to be disbursed within the next 12 months.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect certain reported amounts and disclosures. These estimates include, but are not limited to, allowances for accounts receivable, workers compensation-related assets and liabilities, health plan assets and liabilities, recoverability of goodwill and other intangible assets, income taxes, stock-based compensation and other contingent liabilities. Such estimates are based on historical experience and on various other assumptions that Company management believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Revenue Recognition

Professional service revenues represent fees charged to clients for processing HR transactions on behalf of the Company’s clients, such as payroll payments and remitting employment tax withholding amounts, providing access to the Company’s HR expertise, including HR templates, best practices, and interactions with our HR professionals, providing labor, employment and benefit law compliance services to assist clients in avoiding or reducing liability and exposure and providing additional services, including recruiting or other services, to support various stages of clients’ growth. Professional service revenues are recognized in the period the services are rendered and earned under service arrangements with clients where service fees are fixed or determinable and collectability is reasonably assured.

Insurance service revenues consist of insurance-related billings and administrative fees collected from clients and withheld from WSEs for Company-sponsored, risk-based, fully-insured insurance plans provided through third-party insurance carriers, primarily employee health benefit insurance and workers compensation insurance. Insurance service revenues are recognized in the period amounts are due and collectability is reasonably assured.

The professional service revenues and insurance service revenues are each considered separate units of accounting and the associated fees and insurance premiums are billed as such for the majority of the Company’s clients. For clients billed through a bundled invoice, the selling price of significant deliverables is determined based on the best estimate of the selling price.

The Company is not the primary obligor for payroll and payroll tax payments and, therefore, these payments are not reflected as either revenue or expense. The gross payroll and payroll tax payments made on behalf of the clients, combined, were $30.6 billion, $25.6 billion and $17.6 billion for the years ended December 31, 2015, 2014, and 2013, respectively.

The Company records a liability relating to work performed by WSEs but unpaid at the end of each period in the period in which the WSEs perform work, along with the related receivable for the same period. The Company generally charges an upfront non-refundable set-up fee for which the performance of onboarding services is not a discrete earnings event, and therefore the revenue is recognized on a straight-line basis over the estimated average client tenure.

Insurance Costs

Insurance premiums paid to the insurance carriers for the insurance coverage for clients and WSEs and the reimbursements paid to the insurance carriers or third-party administrators for claims payments made on the Company’s behalf within its insurance deductible layer, where applicable, are included in cost and operating expenses as insurance costs.

Workers Compensation Insurance Reserves

Workers compensation insurance reserves are established to provide for the estimated ultimate costs of paying claims within the deductible layer in accordance with workers compensation insurance policies. These reserves include estimates for reported losses, plus amounts for those claims incurred but not paid, and estimates of certain expenses associated with processing and settling the claims. In establishing the workers compensation insurance reserves, the Company uses an independent actuarial estimate of undiscounted future cash payments that would be made to settle the claims. In the Company's experience, plan years related to workers compensation programs may take up to 10 years or more to be settled.

In estimating these reserves, the Company utilizes historical loss experience, exposure data, and actuarial judgment, together with a range of inputs which are primarily based upon the WSE job responsibilities, their location, the historical frequency and severity of workers compensation claims, and an estimate of future cost trends. All of these components could materially impact the reserves as reported in the consolidated financial statements. For each reporting period, changes in the actuarial assumptions resulting from changes in actual claims experience and other trends are incorporated into the workers compensation claims cost estimates. Accordingly, final claim settlements may vary materially from the present estimates, particularly when those payments may not occur until well into the future.

The Company regularly reviews the adequacy of workers compensation insurance reserves. Adjustments to previously established reserves are reflected in the results of operations for the period in which the adjustment is identified. Such adjustments could be significant, reflecting any variety of new and adverse or favorable trends. Any unexpected increases in the severity or frequency of claims could result in material adverse effects to the operating results.

The Company does not discount loss reserves accrued under these programs. Claim costs expected to be paid within one year are recorded as accrued workers compensation costs and included in short-term worksite employee related liabilities or short term worksite related assets if funds are held by third parties to cover the claims, while costs expected to be paid beyond one year are included in long-term liabilities or long term workers compensation receivables if funds are held by third parties to cover the claims on the consolidated balance sheets. Assets held by third parties to cover claim liabilities remain restricted until the plan year to which they relate are settled.

At policy inception, annual premiums are estimated based on projected wages over the duration of the policy period. As actual wages are realized, the amounts paid for premiums may differ from the estimates recorded by the Company, creating an asset or liability throughout the policy year. Such differences could have a material effect on the Company’s consolidated financial position and results of operations.

Health Benefits

Health benefits insurance reserves are established to provide for the estimated costs of reimbursing the carriers for paying claims within the deductible layer in accordance with health insurance policies. These reserves include estimates for reported losses, plus estimates for claims incurred but not reported. Reserves are determined regularly by the Company based upon a number of factors, including but not limited to actuarial calculations, current and historical claims payment patterns, plan enrollment and medical trend rates. Ultimate health insurance reserves may vary in subsequent years from the amounts estimated. As of December 31, 2015 and 2014, liability reserves of $113.2 million and $82.1 million, respectively, were recorded within health benefits payable and are included in WSE-related liabilities in the accompanying consolidated balance sheets.

Under certain contracts, based on plan performance, the Company may be entitled to receive refunds of premiums. We estimate these refunds based on premium and claims data and record these within prepaid health plan expenses and are included in WSE-related assets on the consolidated balance sheet. As of December 31, 2015 and 2014, the Company had $6.8 million and $4.9 million, respectively, as prepaid health plan expenses included within WSE-related assets.

Cash and Cash Equivalents

Cash and cash equivalents include bank deposits and short-term, highly liquid investments. Investments with original maturity dates of three months or less are considered cash equivalents.

Investments

The Company classifies its investments as available-for-sale and are carried at fair value. Unrealized gains and losses are reported as a component of accumulated other comprehensive income. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts from the date of purchase to maturity or sale. Such amortization is included in interest income as an addition to or deduction from the coupon interest earned on the investments. The Company uses the specific identification method of determining the cost basis in computing realized gains and losses on the sale of its available-for-sale securities. Realized gains and losses are included in other income in the accompanying consolidated statement of operations.

The Company assesses whether an other-than-temporary impairment loss has occurred due to declines in fair value or other market conditions. With respect to debt securities, this assessment takes into account our current intent to sell, or not sell, the security, and whether it is more likely than not that we will not be required to sell the security before recovery of its amortized cost.

Accounts Receivable

The Company’s accounts receivable, which represent outstanding gross billings to clients, are reported net of an allowance for doubtful accounts. The Company establishes an allowance for doubtful accounts based on historical experience, the age of the accounts receivable balances, credit quality of clients, current economic conditions and other factors that may affect clients’ ability to pay, and charges off amounts when they are deemed uncollectible.

Property and Equipment

The Company records property and equipment at historical cost and computes depreciation using the straight-line method over the estimated useful lives of the assets or the lease terms, generally three to five years for software and office equipment, five to seven years for furniture and fixtures, and the shorter of the asset life or the remaining lease term for leasehold improvements. The Company expenses the cost of maintenance and repairs as incurred and capitalizes betterments.

Internal Use Software

The Company capitalizes internal and external costs incurred to develop internal-use computer software during the application development stage. Application development stage costs include license fees paid to third-parties for software use, software configuration, coding, and installation. Capitalized costs are amortized on a straight-line basis over the estimated useful life, typically ranging from three to five years, commencing when the software is placed into service. The Company expenses costs incurred during the preliminary project stage, as well as general and administrative, overhead, maintenance and training costs, and costs that do not add functionality to existing systems. For the years ended December 31, 2015, 2014 and 2013, internally developed software costs capitalized were $11.2 million, $6.3 million and $3.3 million respectively.

Goodwill and Other Intangible Assets

The Company’s goodwill and identifiable intangible assets with indefinite useful lives are not amortized, but instead are tested for impairment on an annual basis or when an event occurs or circumstances change in a way to indicate that there has been a potential decline in the fair value of the reporting unit. Impairment is determined by comparing the estimated fair value of the reporting unit to its carrying amount, including goodwill. The Company’s business is largely homogeneous and, as a result, all goodwill is associated with the Company’s one reportable segment.

Intangible assets with finite useful lives include purchased client lists, trade names, developed technologies, and contractual agreements. Intangible assets are amortized over their respective estimated useful lives ranging from two to six years using either the straight-line method or an accelerated method. Intangible assets are reviewed for indicators of impairment at least annually and evaluated for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Based on the results of the Company’s reviews, no impairment loss was recognized in the results of operations for the years ended December 31, 2015, 2014 and 2013.

Annually, the Company performs a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit has declined below carrying value. This assessment considers various financial, macroeconomic, industry, and reporting unit specific qualitative factors. The Company performs its annual impairment testing in its fiscal fourth quarter. Based on the results of the Company’s reviews, no impairment loss was recognized in the results of operations for the years ended December 31, 2015, 2014 and 2013.

Impairment of Long-Lived Assets

The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. An asset is considered impaired if the carrying amount exceeds the undiscounted future net cash flows the asset is expected to generate. An impairment charge is recognized for the amount by which the carrying amount of the assets exceeds its fair value. Assets to be disposed of are reported at the lower of the carrying amount or fair value, less selling costs.

Advertising Costs

The Company expenses the costs of producing advertisements at the time production occurs, and expenses the cost of running advertisements in the period in which the advertising space or airtime is used as sales and marketing expense. Advertising costs were $8.2 million, $7.3 million, and $7.5 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Stock-Based Compensation

The Company has issued three types of stock-based awards to employees: restricted stock units, stock options and employee stock purchase plan. Compensation expense associated with restricted stock units is based on the fair value of common stock on the date of grant. Compensation expense associated with stock options and employee stock purchase plan are based on the estimated grant date fair value method using the Black-Scholes valuation model. Expense is recognized using a straight-line amortization method over the respective vesting period for awards that are ultimately expected to vest. Accordingly, stock-based compensation has been reduced for estimated forfeitures. When estimating forfeitures, the Company considers voluntary termination behaviors as well as trends of actual option forfeitures. A tax benefit from stock-based compensation is recognized in equity to the extent that an incremental tax benefit is realized.

Income Taxes

The Company recognizes deferred tax assets and liabilities for estimated future tax effects based on differences between the carrying amounts of assets and liabilities for financial reporting purposes and amounts used for income tax purposes under current tax laws. Deferred tax expense results from the change in the net liability for deferred income taxes between periods.

The Company maintains a reserve for uncertain tax positions. The Company evaluates tax positions taken or expected to be taken in a tax return for recognition in its consolidated financial statements. Prior to recording the related tax benefit in the consolidated financial statements, the Company must conclude that tax positions are more likely than not to be sustained, assuming those positions will be examined by taxing authorities with full knowledge of all relevant information. The benefit recognized in the consolidated financial statements is the amount the Company expects to realize after examination by taxing authorities. If a tax position drops below the more likely than not standard, the benefit can no longer be recognized. Assumptions, judgment and the use of estimates are required in determining if the more likely than not standard has been met when developing the provision for income taxes and in determining the expected benefit. A change in the assessment of the more likely than not standard could materially impact the Company’s results of operations or financial position. The Company recognizes interest and penalties related to uncertain tax positions as a component of income tax expense.

Concentrations of Credit Risk

Financial instruments that subject the Company to concentrations of credit risk include cash and cash equivalents, investments, restricted cash and restricted investments (including payroll funds collected), accounts receivable, and amounts due from insurance carriers. The Company maintains its cash and cash equivalents, investments, restricted cash and restricted investments (including payroll funds collected) principally in domestic financial institutions and performs periodic evaluations of the relative credit standing of these institutions. The Company’s exposure to credit risk in the event of default by the financial institutions holding these funds is limited to amounts currently held by the institution in excess of insured amounts.

Under the terms of professional services agreements, clients agree to maintain sufficient funds or other satisfactory credit at all times to cover the cost of its current payroll, all accrued paid time off, vacation or sick leave balances, and other vested wage and benefit obligations for all their work site employees. The Company generally requires payment from its clients on or before the applicable payroll date.

For certain clients, the Company requires an indemnity guarantee payment (IGP) supported by a letter of credit, bond, or a certificate of deposit from certain financial institutions. The IGP typically equals the total payroll and service fee for one average payroll period.

As of December 31, 2015 and December 31, 2014, one client accounted for 12% of accounts receivable. No client accounted for more than 10% of total revenues in the years ended December 31, 2015, 2014 and 2013. Bad debt expense, net of recoveries was $2.0 million, $1.4 million and $0.6 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Recent Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board, or (FASB), issued Accounting Standards Update (ASU) 2016-02—Leases. The amendment requires that lease arrangements longer than 12 months result in an entity recognizing an asset and liability. The amendment is effective for annual reporting periods, and interim periods within those years beginning after December 15, 2018. Early adoption is permitted. The Company is currently in the process of evaluating the impact of the adoption of this standard on its consolidated financial statements.

In January 2016, the FASB issued ASU 2016-01—Recognition and Measurement of Financial Assets and Financial Liabilities. The amendment addresses various aspects of the recognition, measurement, presentation, and disclosure for financial instruments. The amendment is effective for annual reporting periods, and interim periods within those years beginning after December 15, 2017. Early adoption by public entities is permitted only for certain provisions. The Company is currently in the process of evaluating the impact of the adoption of this standard on its consolidated financial statements.

In November 2015, the FASB issued ASU 2015-17—Balance Sheet Classification of Deferred Taxes, as part of its initiative to reduce complexity in accounting standards (the Simplification Initiative). The amendment requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early adoption is permitted. The Company adopted this guidance in 2015 with retrospective application. See Note 11 for further details.

In April 2015, the FASB issued ASU 2015-05—Intangibles—Goodwill and Other—Internal-Use Software, as part of the Simplification Initiative. The amendment provides guidance to clarify the customer’s accounting for fees paid in a cloud computing arrangement. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. The Company expects to adopt this guidance in 2016. The Company does not expect this guidance to have a material effect on its consolidated financial statements.

In April 2015, the FASB issued ASU 2015-03—Interest—Imputation of Interest, as part of its Simplification Initiative. The amendment requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The Company expects to adopt this guidance in 2016. The Company does not expect this guidance to have a material effect on its consolidated financial statements.

In August 2014, the FASB issued ASU 2014-15—Presentation of Financial Statements—Going Concern (Subtopic 205-40), which addresses management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. Management’s evaluation should be based on relevant conditions and events that are known and reasonably knowable at the date that the financial statements are issued. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company does not expect to adopt this guidance early and does not believe that the adoption of this guidance will have a material effect on its consolidated financial statements.

In June 2014, the FASB issued ASU 2014-12—Compensation—Stock Compensation, which requires that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. ASU 2014-12 is effective for annual reporting periods, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted. The amendments may be applied prospectively to all awards granted or modified after the effective date or retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented. The Company does not expect this guidance to have a material effect on its consolidated financial statements. The Company expects to adopt this guidance in 2016.

In May 2014, the FASB issued ASU 2014-09—Revenue from Contracts with Customers, which will replace most existing revenue recognition guidance under GAAP. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard provides a five-step analysis of transactions to determine when and how revenue is recognized. In July 2015, the FASB deferred the effective date to annual reporting periods, and interim periods within those years, beginning after December 15, 2017. Early adoption at the original effective date of December 15, 2016 is permitted. The amendments may be applied retrospectively or as a cumulative-effect adjustment as of the date of adoption. The Company has not yet selected a method of adoption and is currently evaluating the effect that the amendments will have on the consolidated financial statements.