Bad debt expense net of recoveries.

No definition available.

Name:	tnet_BadDebtExpenseNetOfRecoveries
Namespace Prefix:	tnet_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Disclosure of the extent of enterprise reliance on its major customers. For example, includes revenues from transactions with a single external customer amounting to 10 percent or more of the entity's revenues, the total amount of revenues from each such customer, and the identity of the segment or segments reporting the revenues. A group of entities that the entity knows to be under common control generally will be considered a single customer for inclusion in this item.

+ References

No definition available.

+ Details

Name:	tnet_CustomerConcentration
Namespace Prefix:	tnet_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	tnet_PrepaidHealthPlanExpenses
Namespace Prefix:	tnet_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	tnet_SummaryOfSignificantAccountingPolicyLineItems
Namespace Prefix:	tnet_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 720

-SubTopic 35

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

+ Details

Name:	us-gaap_AdvertisingExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Additions made to capitalized computer software costs during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16265-109275

+ Details

Name:	us-gaap_CapitalizedComputerSoftwareAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13537-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13531-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 3

-Subparagraph (a),(b),(c)

-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

+ Details

Name:	us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Payments of cash to employees, including wages and salaries, during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

Name:	us-gaap_PaymentsToEmployees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Description of Business and Significant Accounting Policies - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policy [Line Items]
Number of reportable segments as result of acquisitions	1us-gaap_NumberOfReportableSegments
Gross payroll and payroll tax payments made	$ 25,600,000,000us-gaap_PaymentsToEmployees	$ 17,600,000,000us-gaap_PaymentsToEmployees	$ 10,000,000,000us-gaap_PaymentsToEmployees
Health benefits payable	82,100,000	46,600,000
Prepaid health plan expenses	4,900,000tnet_PrepaidHealthPlanExpenses	7,600,000tnet_PrepaidHealthPlanExpenses
Useful life of finite lived intangible assets	4 years	4 years
Internally developed software costs	6,300,000	3,300,000	4,300,000
Impairment loss	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss
Advertising costs	7,300,000us-gaap_AdvertisingExpense	7,500,000us-gaap_AdvertisingExpense	6,400,000us-gaap_AdvertisingExpense
Customer Concentration Risk
Summary Of Significant Accounting Policy [Line Items]
Bad debt expense, net of recoveries	$ 1,400,000	$ 600,000	$ 400,000
Customer Concentration Risk \| Accounts Receivable
Summary Of Significant Accounting Policy [Line Items]
Concentration risk, percentage	12.00%
Number of customers accounted for more than 10%	1
Customer Concentration Risk \| Accounts Receivable \| Customer One
Summary Of Significant Accounting Policy [Line Items]
Concentration risk, percentage		15.00%
Number of customers accounted for more than 10%		1
Customer Concentration Risk \| Accounts Receivable \| Customer Two
Summary Of Significant Accounting Policy [Line Items]
Concentration risk, percentage		13.00%
Number of customers accounted for more than 10%		1
Customer Concentration Risk \| Service Revenues
Summary Of Significant Accounting Policy [Line Items]
Concentration risk, percentage	10.00%	10.00%	10.00%
Number of customers accounted for more than 10%	0	0	0
Maximum
Summary Of Significant Accounting Policy [Line Items]
Useful life of finite lived intangible assets	6 years
Maximum \| Software Development
Summary Of Significant Accounting Policy [Line Items]
Useful life of finite lived intangible assets	5 years
Maximum \| Software and Office Equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life	5 years
Maximum \| Furniture, fixtures, and equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life	7 years
Maximum \| Geographic Concentration Risk \| Sales Revenue, Net
Summary Of Significant Accounting Policy [Line Items]
Concentration risk, percentage	1.00%
Minimum
Summary Of Significant Accounting Policy [Line Items]
Useful life of finite lived intangible assets	2 years
Minimum \| Software Development
Summary Of Significant Accounting Policy [Line Items]
Useful life of finite lived intangible assets	3 years
Minimum \| Software and Office Equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life	3 years
Minimum \| Furniture, fixtures, and equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life	5 years