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Stockholders' Equity - Additional Information (Details) (USD $)
 1 Months Ended 12 Months Ended 1 Months Ended 0 Months Ended
Dec. 31, 2013
Aug. 31, 2013
Mar. 31, 2013
Nov. 30, 2012
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Mar. 31, 2012
Dec. 31, 2012
Feb. 28, 2014
Mar. 31, 2014
Nov. 30, 2014
Dec. 31, 2009
May 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Aggregate offering price         $ 217,796,000us-gaap_StockIssuedDuringPeriodValueNewIssues                  
Stock options granted percentage of fair market value         110.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent                  
Plan description         Options issued to recipients other than nonemployee directors generally vest over four years with a one year cliff and monthly thereafter, and have a maximum contractual term of 10 years.                  
Term of stock options         4 years                  
Weighted-average grant-date fair value of stock options granted         $ 7.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 4.11us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 1.51us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue              
Total fair value of options vested         7,500,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1 4,000,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1 3,600,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1              
Total intrinsic value of options exercised         35,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 52,600,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 6,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue              
Cash received from options exercised         2,200,000us-gaap_EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions 7,100,000us-gaap_EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions 5,400,000us-gaap_EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions              
Unrecognized compensation expense, net of forfeitures         22,500,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions                  
Unrecognized compensation expense, expected to be recognized over a weighted-average period         2 years 9 months 15 days                  
Total grant date fair value of restricted stock units granted         700,000tnet_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodFairValue                  
Shares Paid for Tax Withholding for Share Based Compensation         80,599us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation 809,012us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation 15,724us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation              
Stock-based compensation expense         11,000,000us-gaap_AllocatedShareBasedCompensationExpense 6,100,000us-gaap_AllocatedShareBasedCompensationExpense 4,400,000us-gaap_AllocatedShareBasedCompensationExpense              
Income tax benefit recognized relating to stock-based compensation expense         2,000,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense 4,400,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense 1,700,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense              
Actual tax benefit realized from stock options exercised         13,500,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions 19,900,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions 2,400,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions              
Dividend declared month and year 2013-12 2013-08       2013-12   2012-03            
Dividend paid to holder of preferred and common stock           357,520,000us-gaap_Dividends 75,450,000us-gaap_Dividends              
Dividend paid to holder of preferred stock 33,300,000us-gaap_DividendsPreferredStock                          
Dividend paid to holder of common stock 13,400,000us-gaap_DividendsCommonStock                          
Exercise prices on outstanding options $ 1.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice       $ 6.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 1.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice                
Stock option exercise price modification terms The Company adjusted the exercise prices on all outstanding options downward by $0.88, exactly equal to the amount of the dividend, except in three instances in which: i) the exercise price was lower than $1.38, ii) the holder of the incentive stock option under the 2009 Plan did not consent to the adjustment when consent was required, or iii) the incentive stock option was under the 2000 Plan. For options that were priced lower than $2.75, the Company adjusted the exercise price to $0.50 The Company adjusted the exercise prices on all outstanding options downward by $5.88, exactly equal to the amount of the dividend, except in three instances in which: i) the exercise price was lower than $6.38, ii) the holder of the incentive stock option under the 2009 Plan did not consent to the adjustment when consent was required, or iii) the incentive stock option was under the 2000 Plan. For options that were priced lower than $6.38, the Company adjusted the exercise price to $0.50         the Company adjusted the exercise prices on all outstanding options downward by $1.57, exactly equal to the amount of the dividend, except in three instances in which: (i) the incentive stock option exercise price was lower than $0.79, (ii) the non-qualified stock option exercise price was lower than $2.07, or (iii) the holder did not consent to the adjustment when consent was required. For incentive stock options that were priced lower than $0.79 and non-qualified stock options priced lower than $2.07, the Company adjusted the exercise price to $0.22 and $0.50 respectively, and increased the number of shares to maintain the ratio of strike price to stock value pre- and post-adjustment.              
Additional stock repurchase program authorized amount                       30,000,000tnet_AdditionalStockRepurchaseProgramAuthorizedAmount    
Number of shares repurchased     407,728us-gaap_StockRepurchasedDuringPeriodShares 608,540us-gaap_StockRepurchasedDuringPeriodShares 490,419us-gaap_StockRepurchasedDuringPeriodShares                  
Value of shares repurchased         15,000,000us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings                  
Stock repurchase remained available for future repurchase, value         30,000,000us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1                  
Offered to repurchase, price per share     $ 8.20us-gaap_TreasuryStockAcquiredAverageCostPerShare $ 4.31us-gaap_TreasuryStockAcquiredAverageCostPerShare                    
Value of shares repurchased     3,300,000us-gaap_StockRepurchasedDuringPeriodValue 2,600,000us-gaap_StockRepurchasedDuringPeriodValue 16,440,000us-gaap_StockRepurchasedDuringPeriodValue 11,985,000us-gaap_StockRepurchasedDuringPeriodValue 2,683,000us-gaap_StockRepurchasedDuringPeriodValue              
Stock repurchased program expiry date     May 31, 2013 Dec. 31, 2012                    
Stockholders' equity note, stock split         On March 7, 2014, the Company’s board of directors and stockholders approved and effected an amendment to the amended and restated certificate of incorporation providing for a 2-for-1 stock split of the outstanding common stock. All of the share numbers, share prices, and exercise prices have been adjusted within these financial statements, on a retroactive basis, to reflect this 2-for-1stock split.                  
Stockholders' equity note, stock split ratio         200.00%tnet_StockholdersEquityNoteStockSplitRatio                  
Cash proceeds from employee purchase of shares         3,393,000us-gaap_ProceedsFromStockPlans                  
Employee Stock Option                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
ESPP approved a reserve of shares of common stock for future issuance         1,100,000us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_EmployeeStockOptionMember		                  
Common stock for future issuance number increase 1,800,000tnet_CommonStockForFutureIssuanceNumberIncrease
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_EmployeeStockOptionMember		         1,800,000tnet_CommonStockForFutureIssuanceNumberIncrease
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_EmployeeStockOptionMember		                
Stock options granted percentage of fair market value on offering date         85.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_EmployeeStockOptionMember		                  
Stock options granted percentage of fair market value on purchase date         85.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_EmployeeStockOptionMember		                  
Employee stock purchase plan offering periods         Offering periods are six months in duration and end on or about May 15 and November 15 of each year, with the exception of the initial offering period which commenced on March 26, 2014 and ended on November 14, 2014.                  
Employee Stock Purchase Plan                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Common stock for future issuance percentage increased         1.00%tnet_CommonStockForFutureIssuancePercentageIncreased
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= tnet_EmployeeStockPurchasePlanMember		                  
Number of shares purchased by employees         249,494us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= tnet_EmployeeStockPurchasePlanMember		                  
Stock purchase price per share         $ 13.6us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= tnet_EmployeeStockPurchasePlanMember		                  
Cash proceeds from employee purchase of shares         3,400,000us-gaap_ProceedsFromStockPlans
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= tnet_EmployeeStockPurchasePlanMember		                  
All outstanding except in three instances in which (i) the incentive stock option exercise price was lower than $0.79, (ii) the non-qualified stock option exercise price was lower than $2.07, or (iii) the holder did not consent to the adjustment when consent was required                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Adjustment to exercise prices on outstanding options             $ (1.57)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingPeriodIncreaseDecreaseWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionThreeMember		              
For non qualified stock option exercise price lower than $2.07                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options             $ 0.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionFiveMember		   $ 0.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionFiveMember		       $ 2.07us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionFiveMember		  
For incentive stock option exercise price lower than $0.79                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options             $ 0.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionFourMember		   $ 0.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionFourMember		          
All outstanding options except in three instances in which (i) the exercise price was lower than $6.38,( ii) the holder of the incentive stock option under the 2009 Plan did not consent to the adjustment when consent was required, or iii) the incentive stock option was under the 2000 Plan.                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Adjustment to exercise prices on outstanding options   (5.88)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingPeriodIncreaseDecreaseWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionSixMember		                        
For options priced lower than $6.38                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options   0.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionSevenMember		                        
All outstanding options except in three instances in which i) the exercise price was lower than $1.38, ii) the holder of the incentive stock option under the 2009 Plan did not consent to the adjustment when consent was required, or iii) the incentive stock option was under the 2000 Plan                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Adjustment to exercise prices on outstanding options $ (0.88)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingPeriodIncreaseDecreaseWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionEightMember		                          
For options priced lower than $2.75                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options         $ 0.50us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_StatementScenarioAxis
= tnet_AdjustedExercisePriceOptionNineMember		                  
Exercise Price Range 1                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options                         $ 0.79us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= tnet_ExercisePriceRange1Member		  
Exercise Price Range 2                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options                         $ 6.38us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= tnet_ExercisePriceRange2Member		  
Exercise Price Range 4                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Exercise prices on outstanding options                         $ 2.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= tnet_ExercisePriceRange4Member		  
Preferred Stock                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Dividend declared per share $ 0.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		 5.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		       $ 0.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		   $ 1.57us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		            
Dividend payable date of record Dec. 25, 2013 Aug. 21, 2013           Mar. 30, 2012            
Dividend paid to holder of preferred and common stock   223,600,000us-gaap_Dividends
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		           59,500,000us-gaap_Dividends
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		            
Dividends Payable, Date to be Paid, Year and Month 2013-12 2013-08       2013-12   2012-03            
Common Stock                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Initial public offering shares issued and sold         15,091,074us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		                  
Aggregate offering price         217,796,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		                  
Dividend declared per share $ 0.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		 5.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		       $ 0.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		   $ 1.57us-gaap_DividendsPayableAmountPerShare
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		            
Dividend payable date of record Dec. 25, 2013 Aug. 30, 2013           May 15, 2012            
Dividend paid to holder of preferred and common stock   87,100,000us-gaap_Dividends
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		           15,900,000us-gaap_Dividends
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		            
Dividends Payable, Date to be Paid, Year and Month   2013-09           2012-05            
Number of shares repurchased         571,018us-gaap_StockRepurchasedDuringPeriodShares
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		 1,216,740us-gaap_StockRepurchasedDuringPeriodShares
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		 624,264us-gaap_StockRepurchasedDuringPeriodShares
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		              
Number of shares purchased by employees         249,494us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		                  
Restricted Stock Units                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Plan description         The fair value of restricted stock units is equal to the fair value of the Company’s common stock on the date of grant. The restricted stock units vest at a rate of 25% at the end of the first year and then pro rata monthly thereafter over the remaining vesting term of three or two years, as applicable.                  
Unrecognized compensation expense, net of forfeitures         100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		                  
Unrecognized compensation expense, expected to be recognized over a weighted-average period         2 years 6 months                  
Total grant date fair value of restricted stock units         100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		              
Dividend declared per share $ 0.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 5.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		       $ 0.88us-gaap_DividendsPayableAmountPerShare
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		   $ 1.57us-gaap_DividendsPayableAmountPerShare
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		            
Dividend, share based compensation   100,000us-gaap_DividendsShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		           100,000us-gaap_DividendsShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 100,000us-gaap_DividendsShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		          
Maximum                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Contractual term         5 years                  
Stock repurchase program authorized amount                           15,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Share repurchase, number of shares to be repurchased     1,800,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 2,200,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		                    
Employees contribution on earnings         15.00%tnet_EmployeesContributionOnEarnings
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		                  
Maximum | Restricted Stock Units                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Term of stock options         3 years                  
Minimum                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Ownership percentage         10.00%tnet_StockholderOwnership
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		                  
Employees contribution on earnings         1.00%tnet_EmployeesContributionOnEarnings
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		                  
Minimum | Restricted Stock Units                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Term of stock options         2 years                  
Stock options vesting percentage         25.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		                  
2009 Plan                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Additional shares available for grant                   3,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= tnet_TwoThousandNineEquityIncentivePlanMember		        
Shares reserved for future issuance expressed as a percentage of outstanding shares                   4.50%tnet_SharesReservedForFutureIssuanceExpressedAsPercentageOfOutstandingShares
/ us-gaap_PlanNameAxis
= tnet_TwoThousandNineEquityIncentivePlanMember		        
Member of Board of Directors                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Initial public offering shares issued and sold                   91,074us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember		        
Public offering share price                   10.98us-gaap_SharesIssuedPricePerShare
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember		        
Aggregate offering price                   1,000,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember		        
Nonemployee Directors | Maximum                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Contractual term         10 years                  
Nonemployee Directors | 2009 Plan                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Plan description         The amended 2009 Plan also provides that the number of shares reserved for issuance under the 2009 Plan will increase on January 1 of each year for a period of up to five years by 4.5% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, which will begin on January 1, 2015 and continue through January 1, 2019.                  
Initial Public Offering                            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Initial public offering shares issued and sold                     15,000,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember		      
Public offering share price                     $ 16us-gaap_SharesIssuedPricePerShare
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember		      
Aggregate offering price                     240,000,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember		      
Proceeds from initial public offering net of underwriting discounts, commissions and offering expenses                     217,800,000us-gaap_ProceedsFromIssuanceInitialPublicOffering
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember		      
Underwriting discounts and commissions                     16,800,000tnet_PaymentOfUnderwritingDiscountsAndCommissions
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember		      
Offering expenses                     $ 5,600,000us-gaap_PaymentsOfStockIssuanceCosts
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember