Worksite Employee-Related Assets and Liabilities - Schedule of Components of the Company's WSE-Related Assets and WSE-Related Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Worksite employee-related assets:
Restricted cash	$ 14,546	$ 14,543
Total worksite employee-related assets	922,619tnet_WorkSiteEmployeeRelatedAssets	1,635,136tnet_WorkSiteEmployeeRelatedAssets
Worksite employee-related liabilities:
Health benefits payable	27,415us-gaap_AccruedEmployeeBenefitsCurrent	29,179us-gaap_AccruedEmployeeBenefitsCurrent
Workers compensation payable	61,591	36,778
Total worksite employee-related liabilities	915,985tnet_WorkSiteEmployeeRelatedLiabilities	1,630,555tnet_WorkSiteEmployeeRelatedLiabilities
WSE
Worksite employee-related assets:
Restricted cash	78,763	64,890
Restricted investment	2,441	4,555
Payroll funds collected	502,306	1,336,994
Unbilled revenue, net of advance collections of $59,877 and $113,190 at March 31, 2015 and December 31, 2014, respectively	309,327	203,599
Accounts receivable, net of allowance for doubtful accounts of $288 and $388 at March 31, 2015 and December 31, 2014, respectively	11,253	5,193
Prepaid health plan expenses	5,527	4,932
Prepaid workers compensation expenses	1,562	1,256
Other payroll assets	6,055	5,742
Total worksite employee-related assets	922,619	1,635,136
Worksite employee-related liabilities:
Unbilled wages accrual	345,955	292,906
Payroll taxes payable	326,665	1,119,427
Health benefits payable	105,235	104,220
Customer prepayments	48,549	53,770
Workers compensation payable	61,591	36,778
Other payroll deductions	27,990	23,454
Total worksite employee-related liabilities	915,985	1,630,555
WSE \| Workers Compensation
Worksite employee-related assets:
Refundable premiums	$ 5,385	$ 7,975

Accrued unpaid payroll costs for worksite employees.

No definition available.

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Funds set aside to cover worksite employee related liabilities.

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No definition available.

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Consists of premium stabilization reserves with participating health insurance carriers, which exist when premiums paid exceed the total of claims and other charges.

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No definition available.

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Workers' compensation premiums paid in advance for the current plan year.

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Assets arising from the servicing of client payroll, including unbilled revenue and payroll funds collected.

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No definition available.

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Liabilities arising from the servicing of client payroll, including unbilled wages accrual and payroll taxes payable.

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No definition available.

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Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying value as of the balance sheet date of obligations incurred and payable for statutory payroll taxes incurred through that date and withheld from employees pertaining to services received from them, including entity's matching share of the employees FICA taxes and contributions to the state and federal unemployment insurance programs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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The current portion of aggregate prepayments received from customers for goods or services to be provided in the future, as well as the current portion of money or property received from customers that are to be returned upon satisfactory contract completion or as partial prepayment for goods or services to be provided in the future.

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Amount of other miscellaneous assets expected to be realized or consumed within one year or operating cycle, if longer.

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No definition available.

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Carrying value as of the balance sheet date of obligations incurred through that date and payable for employer-related costs not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of asset related to consideration paid in advance for insurance that provides economic benefits within a future period of one year or the normal operating cycle, if longer.

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The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

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This element represents the current portion of investments which are not defined as or included in marketable (debt, equity, or other) securities that are pledged or subject to withdrawal restrictions.

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Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.

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Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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