XML 71 R31.htm IDEA: XBRL DOCUMENT
v3.23.3

INVESTMENTS - Schedule of Financial Instruments by Significant Categories and Fair Value Measurement on a Recurring Basis (Details) - Fair Value Measurement on a Recurring Basis - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Securities |  |
Cash equivalents: | $ 138 | $ 332
Amortized Cost | 469 | 464
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (8) | (4)
Fair Value | 461 | 460
Cash and Cash Equivalents |  |
Debt Securities |  |
Cash equivalents: | 51 | 243
Fair Value | 0 | 0
Investments |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
Fair Value | 219 | 226
Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Cash equivalents: | 87 | 89
Fair Value | 242 | 234
Asset-backed securities | Level 2 |  |
Debt Securities |  |
Amortized Cost | 45 | 42
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (1) | (2)
Fair Value | 44 | 40
Asset-backed securities | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Fair Value | 0 | 0
Asset-backed securities | Level 2 | Investments |  |
Debt Securities |  |
Fair Value | 44 | 40
Asset-backed securities | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Fair Value | 0 | 0
Corporate bonds | Level 2 |  |
Debt Securities |  |
Amortized Cost | 131 | 140
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (1) | (1)
Fair Value | 130 | 139
Corporate bonds | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Fair Value | 0 | 0
Corporate bonds | Level 2 | Investments |  |
Debt Securities |  |
Fair Value | 102 | 112
Corporate bonds | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Fair Value | 28 | 27
Agency securities | Level 2 |  |
Debt Securities |  |
Amortized Cost | 40 | 33
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (1) | (1)
Fair Value | 39 | 32
Agency securities | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Fair Value | 0 | 0
Agency securities | Level 2 | Investments |  |
Debt Securities |  |
Fair Value | 11 | 5
Agency securities | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Fair Value | 28 | 27
U.S. treasuries | Level 2 |  |
Debt Securities |  |
Amortized Cost | 241 | 229
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (5) | 0
Fair Value | 236 | 229
U.S. treasuries | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Fair Value | 0 | 0
U.S. treasuries | Level 2 | Investments |  |
Debt Securities |  |
Fair Value | 57 | 62
U.S. treasuries | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Fair Value | 179 | 167
Certificate of deposit | Level 2 |  |
Debt Securities |  |
Amortized Cost | 7 | 12
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 7 | 12
Certificate of deposit | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Fair Value | 0 | 0
Certificate of deposit | Level 2 | Investments |  |
Debt Securities |  |
Fair Value | 0 | 0
Certificate of deposit | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Fair Value | 7 | 12
Other debt securities | Level 2 |  |
Debt Securities |  |
Amortized Cost | 5 | 8
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 5 | 8
Other debt securities | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Fair Value | 0 | 0
Other debt securities | Level 2 | Investments |  |
Debt Securities |  |
Fair Value | 5 | 7
Other debt securities | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Fair Value | 0 | 1
Money market mutual funds | Level 1 |  |
Debt Securities |  |
Cash equivalents: | 134 | 314
Money market mutual funds | Level 1 | Cash and Cash Equivalents |  |
Debt Securities |  |
Cash equivalents: | 47 | 225
Money market mutual funds | Level 1 | Investments |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
Money market mutual funds | Level 1 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Cash equivalents: | 87 | 89
U.S. treasuries | Level 2 |  |
Debt Securities |  |
Cash equivalents: | 4 | 18
U.S. treasuries | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Cash equivalents: | 4 | 18
U.S. treasuries | Level 2 | Investments |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
U.S. treasuries | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Cash equivalents: | $ 0 | $ 0

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (aa) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481830/320-10-45-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_CashEquivalentsAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_InvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=tnet_RestrictedCashAndCashEquivalentsAndInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |