3.22.0.1 html 483 618 1 false 169 0 false 14 false false R1.htm 0001001 - Document - Cover Page Sheet http://www.tep.com/role/CoverPage Cover Page Cover 1 false false R2.htm 0002002 - Document - Audit Information Sheet http://www.tep.com/role/AuditInformation Audit Information Notes 2 false false R3.htm 1001003 - Statement - CONSOLIDATED STATEMENTS OF INCOME Sheet http://www.tep.com/role/CONSOLIDATEDSTATEMENTSOFINCOME CONSOLIDATED STATEMENTS OF INCOME Uncategorized 3 false false R4.htm 1002004 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS Sheet http://www.tep.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS CONSOLIDATED STATEMENTS OF CASH FLOWS Statements 4 false false R5.htm 1003005 - Statement - CONSOLIDATED BALANCE SHEETS Sheet http://www.tep.com/role/CONSOLIDATEDBALANCESHEETS CONSOLIDATED BALANCE SHEETS Statements 5 false false R6.htm 1004006 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) Sheet http://www.tep.com/role/CONSOLIDATEDBALANCESHEETSParenthetical CONSOLIDATED BALANCE SHEETS (Parenthetical) Statements 6 false false R7.htm 1005007 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDER'S EQUITY Sheet http://www.tep.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDER'S EQUITY Statements 7 false false R8.htm 2101101 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Notes 8 false false R9.htm 2111102 - Disclosure - REGULATORY MATTERS Sheet http://www.tep.com/role/REGULATORYMATTERS REGULATORY MATTERS Notes 9 false false R10.htm 2118103 - Disclosure - UTILITY PLANT AND JOINTLY-OWNED FACILITIES Sheet http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIES UTILITY PLANT AND JOINTLY-OWNED FACILITIES Notes 10 false false R11.htm 2124104 - Disclosure - REVENUE Sheet http://www.tep.com/role/REVENUE REVENUE Notes 11 false false R12.htm 2127105 - Disclosure - ACCOUNTS RECEIVABLE Sheet http://www.tep.com/role/ACCOUNTSRECEIVABLE ACCOUNTS RECEIVABLE Notes 12 false false R13.htm 2130106 - Disclosure - RELATED PARTY TRANSACTIONS Sheet http://www.tep.com/role/RELATEDPARTYTRANSACTIONS RELATED PARTY TRANSACTIONS Notes 13 false false R14.htm 2133107 - Disclosure - DEBT AND CREDIT AGREEMENTS Sheet http://www.tep.com/role/DEBTANDCREDITAGREEMENTS DEBT AND CREDIT AGREEMENTS Notes 14 false false R15.htm 2139108 - Disclosure - LEASES Sheet http://www.tep.com/role/LEASES LEASES Notes 15 false false R16.htm 2147109 - Disclosure - COMMITMENTS AND CONTINGENCIES Sheet http://www.tep.com/role/COMMITMENTSANDCONTINGENCIES COMMITMENTS AND CONTINGENCIES Notes 16 false false R17.htm 2152110 - Disclosure - EMPLOYEE BENEFITS PLANS Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANS EMPLOYEE BENEFITS PLANS Notes 17 false false R18.htm 2169111 - Disclosure - SHARE-BASED COMPENSATION Sheet http://www.tep.com/role/SHAREBASEDCOMPENSATION SHARE-BASED COMPENSATION Notes 18 false false R19.htm 2172112 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION Sheet http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATION SUPPLEMENTAL CASH FLOW INFORMATION Notes 19 false false R20.htm 2176113 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTS FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS Notes 20 false false R21.htm 2184114 - Disclosure - INCOME TAXES Sheet http://www.tep.com/role/INCOMETAXES INCOME TAXES Notes 21 false false R22.htm 2202201 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) Policies 22 false false R23.htm 2303301 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) Tables http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES 23 false false R24.htm 2312302 - Disclosure - REGULATORY MATTERS (Tables) Sheet http://www.tep.com/role/REGULATORYMATTERSTables REGULATORY MATTERS (Tables) Tables http://www.tep.com/role/REGULATORYMATTERS 24 false false R25.htm 2319303 - Disclosure - UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Tables) Sheet http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESTables UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Tables) Tables http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIES 25 false false R26.htm 2325304 - Disclosure - REVENUE (Tables) Sheet http://www.tep.com/role/REVENUETables REVENUE (Tables) Tables http://www.tep.com/role/REVENUE 26 false false R27.htm 2328305 - Disclosure - ACCOUNTS RECEIVABLE (Tables) Sheet http://www.tep.com/role/ACCOUNTSRECEIVABLETables ACCOUNTS RECEIVABLE (Tables) Tables http://www.tep.com/role/ACCOUNTSRECEIVABLE 27 false false R28.htm 2331306 - Disclosure - RELATED PARTY TRANSACTIONS (Table) Sheet http://www.tep.com/role/RELATEDPARTYTRANSACTIONSTable RELATED PARTY TRANSACTIONS (Table) Tables http://www.tep.com/role/RELATEDPARTYTRANSACTIONS 28 false false R29.htm 2334307 - Disclosure - DEBT AND CREDIT AGREEMENTS (Tables) Sheet http://www.tep.com/role/DEBTANDCREDITAGREEMENTSTables DEBT AND CREDIT AGREEMENTS (Tables) Tables http://www.tep.com/role/DEBTANDCREDITAGREEMENTS 29 false false R30.htm 2340308 - Disclosure - LEASES (Tables) Sheet http://www.tep.com/role/LEASESTables LEASES (Tables) Tables http://www.tep.com/role/LEASES 30 false false R31.htm 2348309 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables) Sheet http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESTables COMMITMENTS AND CONTINGENCIES (Tables) Tables http://www.tep.com/role/COMMITMENTSANDCONTINGENCIES 31 false false R32.htm 2353310 - Disclosure - EMPLOYEE BENEFITS PLANS (Tables) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables EMPLOYEE BENEFITS PLANS (Tables) Tables http://www.tep.com/role/EMPLOYEEBENEFITSPLANS 32 false false R33.htm 2370311 - Disclosure - SHARE-BASED COMPENSATION (Tables) Sheet http://www.tep.com/role/SHAREBASEDCOMPENSATIONTables SHARE-BASED COMPENSATION (Tables) Tables http://www.tep.com/role/SHAREBASEDCOMPENSATION 33 false false R34.htm 2373312 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION (Tables) Sheet http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATIONTables SUPPLEMENTAL CASH FLOW INFORMATION (Tables) Tables http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATION 34 false false R35.htm 2377313 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Tables) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Tables) Tables http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTS 35 false false R36.htm 2385314 - Disclosure - INCOME TAXES (Tables) Sheet http://www.tep.com/role/INCOMETAXESTables INCOME TAXES (Tables) Tables http://www.tep.com/role/INCOMETAXES 36 false false R37.htm 2404401 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Additional Information) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESAdditionalInformationDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Additional Information) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 37 false false R38.htm 2405402 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Restricted Cash) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRestrictedCashDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Restricted Cash) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 38 false false R39.htm 2406403 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (AFUDC Rates) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESAFUDCRatesDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (AFUDC Rates) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 39 false false R40.htm 2407404 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Summary of Average Annual Depreciation Rates for All Utility Plants) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSummaryofAverageAnnualDepreciationRatesforAllUtilityPlantsDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Summary of Average Annual Depreciation Rates for All Utility Plants) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 40 false false R41.htm 2408405 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Renewable Energy and Energy Efficiency Programs) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRenewableEnergyandEnergyEfficiencyProgramsDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Renewable Energy and Energy Efficiency Programs) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 41 false false R42.htm 2409406 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Renewable Energy Credits) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRenewableEnergyCreditsDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Renewable Energy Credits) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 42 false false R43.htm 2410407 - Disclosure - NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Taxes) (Details) Sheet http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTaxesDetails NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Taxes) (Details) Details http://www.tep.com/role/NATUREOFOPERATIONSANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables 43 false false R44.htm 2413408 - Disclosure - REGULATORY MATTERS (2020 Rate Order) (Details) Sheet http://www.tep.com/role/REGULATORYMATTERS2020RateOrderDetails REGULATORY MATTERS (2020 Rate Order) (Details) Details http://www.tep.com/role/REGULATORYMATTERSTables 44 false false R45.htm 2414409 - Disclosure - REGULATORY MATTERS (2019 FERC Rate Case) (Details) Sheet http://www.tep.com/role/REGULATORYMATTERS2019FERCRateCaseDetails REGULATORY MATTERS (2019 FERC Rate Case) (Details) Details http://www.tep.com/role/REGULATORYMATTERSTables 45 false false R46.htm 2415410 - Disclosure - REGULATORY MATTERS (Cost Recovery Mechanisms) (Details) Sheet http://www.tep.com/role/REGULATORYMATTERSCostRecoveryMechanismsDetails REGULATORY MATTERS (Cost Recovery Mechanisms) (Details) Details http://www.tep.com/role/REGULATORYMATTERSTables 46 false false R47.htm 2416411 - Disclosure - REGULATORY MATTERS (Regulatory Assets) (Details) Sheet http://www.tep.com/role/REGULATORYMATTERSRegulatoryAssetsDetails REGULATORY MATTERS (Regulatory Assets) (Details) Details http://www.tep.com/role/REGULATORYMATTERSTables 47 false false R48.htm 2417412 - Disclosure - REGULATORY MATTERS (Regulatory Liabilities) (Details) Sheet http://www.tep.com/role/REGULATORYMATTERSRegulatoryLiabilitiesDetails REGULATORY MATTERS (Regulatory Liabilities) (Details) Details http://www.tep.com/role/REGULATORYMATTERSTables 48 false false R49.htm 2420413 - Disclosure - UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Utility Plant in Service by Major Class) (Details) Sheet http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESUtilityPlantinServicebyMajorClassDetails UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Utility Plant in Service by Major Class) (Details) Details http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESTables 49 false false R50.htm 2421414 - Disclosure - UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Narrative) (Details) Sheet http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESNarrativeDetails UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Narrative) (Details) Details http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESTables 50 false false R51.htm 2422415 - Disclosure - UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Jointly-Owned Facilities) (Details) Sheet http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESJointlyOwnedFacilitiesDetails UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Jointly-Owned Facilities) (Details) Details http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESTables 51 false false R52.htm 2423416 - Disclosure - UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Schedule of Changes in Asset Retirement Obligations) (Details) Sheet http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESScheduleofChangesinAssetRetirementObligationsDetails UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Schedule of Changes in Asset Retirement Obligations) (Details) Details http://www.tep.com/role/UTILITYPLANTANDJOINTLYOWNEDFACILITIESTables 52 false false R53.htm 2426417 - Disclosure - REVENUE (Details) Sheet http://www.tep.com/role/REVENUEDetails REVENUE (Details) Details http://www.tep.com/role/REVENUETables 53 false false R54.htm 2429418 - Disclosure - ACCOUNTS RECEIVABLE (Details) Sheet http://www.tep.com/role/ACCOUNTSRECEIVABLEDetails ACCOUNTS RECEIVABLE (Details) Details http://www.tep.com/role/ACCOUNTSRECEIVABLETables 54 false false R55.htm 2432419 - Disclosure - RELATED PARTY TRANSACTIONS (Details) Sheet http://www.tep.com/role/RELATEDPARTYTRANSACTIONSDetails RELATED PARTY TRANSACTIONS (Details) Details http://www.tep.com/role/RELATEDPARTYTRANSACTIONSTable 55 false false R56.htm 2435420 - Disclosure - DEBT AND CREDIT AGREEMENTS (Long-term Debt) (Detail) Sheet http://www.tep.com/role/DEBTANDCREDITAGREEMENTSLongtermDebtDetail DEBT AND CREDIT AGREEMENTS (Long-term Debt) (Detail) Details http://www.tep.com/role/DEBTANDCREDITAGREEMENTSTables 56 false false R57.htm 2436421 - Disclosure - DEBT AND CREDIT AGREEMENTS (Issuances and Redemptions) (Details) Sheet http://www.tep.com/role/DEBTANDCREDITAGREEMENTSIssuancesandRedemptionsDetails DEBT AND CREDIT AGREEMENTS (Issuances and Redemptions) (Details) Details http://www.tep.com/role/DEBTANDCREDITAGREEMENTSTables 57 false false R58.htm 2437422 - Disclosure - DEBT AND CREDIT AGREEMENTS (Maturities of Long-term Debt) (Details) Sheet http://www.tep.com/role/DEBTANDCREDITAGREEMENTSMaturitiesofLongtermDebtDetails DEBT AND CREDIT AGREEMENTS (Maturities of Long-term Debt) (Details) Details http://www.tep.com/role/DEBTANDCREDITAGREEMENTSTables 58 false false R59.htm 2438423 - Disclosure - DEBT AND CREDIT AGREEMENTS (Credit Agreements) (Details) Sheet http://www.tep.com/role/DEBTANDCREDITAGREEMENTSCreditAgreementsDetails DEBT AND CREDIT AGREEMENTS (Credit Agreements) (Details) Details http://www.tep.com/role/DEBTANDCREDITAGREEMENTSTables 59 false false R60.htm 2441424 - Disclosure - LEASES (Assets and Liabilities) (Details) Sheet http://www.tep.com/role/LEASESAssetsandLiabilitiesDetails LEASES (Assets and Liabilities) (Details) Details http://www.tep.com/role/LEASESTables 60 false false R61.htm 2442425 - Disclosure - LEASES (Narrative) (Details) Sheet http://www.tep.com/role/LEASESNarrativeDetails LEASES (Narrative) (Details) Details http://www.tep.com/role/LEASESTables 61 false false R62.htm 2443426 - Disclosure - LEASES (Lease Cost) (Details) Sheet http://www.tep.com/role/LEASESLeaseCostDetails LEASES (Lease Cost) (Details) Details http://www.tep.com/role/LEASESTables 62 false false R63.htm 2444427 - Disclosure - LEASES (Lease Liability) (Details) Sheet http://www.tep.com/role/LEASESLeaseLiabilityDetails LEASES (Lease Liability) (Details) Details http://www.tep.com/role/LEASESTables 63 false false R64.htm 2445428 - Disclosure - LEASES (Term and Rate) (Details) Sheet http://www.tep.com/role/LEASESTermandRateDetails LEASES (Term and Rate) (Details) Details http://www.tep.com/role/LEASESTables 64 false false R65.htm 2446429 - Disclosure - LEASES (Cash Flows) (Details) Sheet http://www.tep.com/role/LEASESCashFlowsDetails LEASES (Cash Flows) (Details) Details http://www.tep.com/role/LEASESTables 65 false false R66.htm 2449430 - Disclosure - COMMITMENTS AND CONTINGENCIES (Commitments) (Details) Sheet http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESCommitmentsDetails COMMITMENTS AND CONTINGENCIES (Commitments) (Details) Details http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESTables 66 false false R67.htm 2450431 - Disclosure - COMMITMENTS AND CONTINGENCIES (Contingencies) (Details) Sheet http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESContingenciesDetails COMMITMENTS AND CONTINGENCIES (Contingencies) (Details) Details http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESTables 67 false false R68.htm 2451432 - Disclosure - COMMITMENTS AND CONTINGENCIES (Performance Guarantees) (Details) Sheet http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESPerformanceGuaranteesDetails COMMITMENTS AND CONTINGENCIES (Performance Guarantees) (Details) Details http://www.tep.com/role/COMMITMENTSANDCONTINGENCIESTables 68 false false R69.htm 2454433 - Disclosure - EMPLOYEE BENEFITS PLANS (Additional Information) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSAdditionalInformationDetails EMPLOYEE BENEFITS PLANS (Additional Information) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 69 false false R70.htm 2455434 - Disclosure - EMPLOYEE BENEFITS PLANS (Pension and Other Postretirement Benefit Amounts included in Consolidated Balance Sheet ) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSPensionandOtherPostretirementBenefitAmountsincludedinConsolidatedBalanceSheetDetails EMPLOYEE BENEFITS PLANS (Pension and Other Postretirement Benefit Amounts included in Consolidated Balance Sheet ) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 70 false false R71.htm 2456435 - Disclosure - EMPLOYEE BENEFITS PLANS (Change in Projected Benefit Obligation and Plan Assets and Reconciliation of Funded Status) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSChangeinProjectedBenefitObligationandPlanAssetsandReconciliationofFundedStatusDetails EMPLOYEE BENEFITS PLANS (Change in Projected Benefit Obligation and Plan Assets and Reconciliation of Funded Status) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 71 false false R72.htm 2457436 - Disclosure - EMPLOYEE BENEFITS PLANS (Components of Regulatory Assets and Accumulated Other Comprehensive Loss Not Recognized as Net Periodic Benefit Cost) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSComponentsofRegulatoryAssetsandAccumulatedOtherComprehensiveLossNotRecognizedasNetPeriodicBenefitCostDetails EMPLOYEE BENEFITS PLANS (Components of Regulatory Assets and Accumulated Other Comprehensive Loss Not Recognized as Net Periodic Benefit Cost) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 72 false false R73.htm 2458437 - Disclosure - EMPLOYEE BENEFITS PLANS (Information for Pension Plans with Accumulated Benefit Obligations in Excess of Pension Plan Assets) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSInformationforPensionPlanswithAccumulatedBenefitObligationsinExcessofPensionPlanAssetsDetails EMPLOYEE BENEFITS PLANS (Information for Pension Plans with Accumulated Benefit Obligations in Excess of Pension Plan Assets) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 73 false false R74.htm 2459438 - Disclosure - EMPLOYEE BENEFITS PLANS (Components of Net Periodic Benefit Cost) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSComponentsofNetPeriodicBenefitCostDetails EMPLOYEE BENEFITS PLANS (Components of Net Periodic Benefit Cost) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 74 false false R75.htm 2460439 - Disclosure - EMPLOYEE BENEFITS PLANS (Changes in Regulatory Assets and Accumulated Comprehensive Income) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSChangesinRegulatoryAssetsandAccumulatedComprehensiveIncomeDetails EMPLOYEE BENEFITS PLANS (Changes in Regulatory Assets and Accumulated Comprehensive Income) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 75 false false R76.htm 2461440 - Disclosure - EMPLOYEE BENEFITS PLANS (Weighted-Average Assumptions Used to Determine Benefit Obligations) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSWeightedAverageAssumptionsUsedtoDetermineBenefitObligationsDetails EMPLOYEE BENEFITS PLANS (Weighted-Average Assumptions Used to Determine Benefit Obligations) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 76 false false R77.htm 2462441 - Disclosure - EMPLOYEE BENEFITS PLANS (Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSWeightedAverageAssumptionsUsedtoDetermineNetPeriodicBenefitCostDetails EMPLOYEE BENEFITS PLANS (Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 77 false false R78.htm 2463442 - Disclosure - EMPLOYEE BENEFITS PLANS (Assumed Health Care Cost Trend Rates) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSAssumedHealthCareCostTrendRatesDetails EMPLOYEE BENEFITS PLANS (Assumed Health Care Cost Trend Rates) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 78 false false R79.htm 2464443 - Disclosure - EMPLOYEE BENEFITS PLANS (Percentage of Pension Plan Assets By Asset Category) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSPercentageofPensionPlanAssetsByAssetCategoryDetails EMPLOYEE BENEFITS PLANS (Percentage of Pension Plan Assets By Asset Category) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 79 false false R80.htm 2465444 - Disclosure - EMPLOYEE BENEFITS PLANS (Fair Value Measurements of Plan Assets By Level) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSFairValueMeasurementsofPlanAssetsByLevelDetails EMPLOYEE BENEFITS PLANS (Fair Value Measurements of Plan Assets By Level) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 80 false false R81.htm 2466445 - Disclosure - EMPLOYEE BENEFITS PLANS (Reconciliation of Changes in Fair Value of Level III Assets) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSReconciliationofChangesinFairValueofLevelIIIAssetsDetails EMPLOYEE BENEFITS PLANS (Reconciliation of Changes in Fair Value of Level III Assets) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 81 false false R82.htm 2467446 - Disclosure - EMPLOYEE BENEFITS PLANS (Target Allocation Percentages for Major Categories of Plan Assets) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTargetAllocationPercentagesforMajorCategoriesofPlanAssetsDetails EMPLOYEE BENEFITS PLANS (Target Allocation Percentages for Major Categories of Plan Assets) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 82 false false R83.htm 2468447 - Disclosure - EMPLOYEE BENEFITS PLANS (Future Benefit Payments) (Details) Sheet http://www.tep.com/role/EMPLOYEEBENEFITSPLANSFutureBenefitPaymentsDetails EMPLOYEE BENEFITS PLANS (Future Benefit Payments) (Details) Details http://www.tep.com/role/EMPLOYEEBENEFITSPLANSTables 83 false false R84.htm 2471448 - Disclosure - SHARE-BASED COMPENSATION (Details) Sheet http://www.tep.com/role/SHAREBASEDCOMPENSATIONDetails SHARE-BASED COMPENSATION (Details) Details http://www.tep.com/role/SHAREBASEDCOMPENSATIONTables 84 false false R85.htm 2474449 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION (Cash Transactions) (Details) Sheet http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATIONCashTransactionsDetails SUPPLEMENTAL CASH FLOW INFORMATION (Cash Transactions) (Details) Details http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATIONTables 85 false false R86.htm 2475450 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION (Non-Cash Transactions) (Details) Sheet http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATIONNonCashTransactionsDetails SUPPLEMENTAL CASH FLOW INFORMATION (Non-Cash Transactions) (Details) Details http://www.tep.com/role/SUPPLEMENTALCASHFLOWINFORMATIONTables 86 false false R87.htm 2478451 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSFinancialInstrumentsMeasuredatFairValueonaRecurringBasisDetails FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) Details http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables 87 false false R88.htm 2479452 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Potential Offset of Counterparty Netting and Cash Collateral) (Details) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSPotentialOffsetofCounterpartyNettingandCashCollateralDetails FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Potential Offset of Counterparty Netting and Cash Collateral) (Details) Details http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables 88 false false R89.htm 2480453 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Impact of Derivative Energy Contracts) (Details) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSFinancialImpactofDerivativeEnergyContractsDetails FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Impact of Derivative Energy Contracts) (Details) Details http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables 89 false false R90.htm 2481454 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Derivative Volumes) (Details) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSDerivativeVolumesDetails FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Derivative Volumes) (Details) Details http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables 90 false false R91.htm 2482455 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Credit Risk) (Details) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSCreditRiskDetails FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Credit Risk) (Details) Details http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables 91 false false R92.htm 2483456 - Disclosure - FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Not Carried at Fair Value) (Details) Sheet http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSFinancialInstrumentsNotCarriedatFairValueDetails FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Not Carried at Fair Value) (Details) Details http://www.tep.com/role/FAIRVALUEMEASUREMENTSANDDERIVATIVEINSTRUMENTSTables 92 false false R93.htm 2486457 - Disclosure - INCOME TAXES (Reconciliation of Differences between Income Tax Expense and Amount Obtained by Multiplying Pre-Tax Income by U.S. Statutory Federal Income Tax Rate) (Details) Sheet http://www.tep.com/role/INCOMETAXESReconciliationofDifferencesbetweenIncomeTaxExpenseandAmountObtainedbyMultiplyingPreTaxIncomebyUSStatutoryFederalIncomeTaxRateDetails INCOME TAXES (Reconciliation of Differences between Income Tax Expense and Amount Obtained by Multiplying Pre-Tax Income by U.S. Statutory Federal Income Tax Rate) (Details) Details http://www.tep.com/role/INCOMETAXESTables 93 false false R94.htm 2487458 - Disclosure - INCOME TAXES (Income Tax Expense Included in Income Statements) (Details) Sheet http://www.tep.com/role/INCOMETAXESIncomeTaxExpenseIncludedinIncomeStatementsDetails INCOME TAXES (Income Tax Expense Included in Income Statements) (Details) Details http://www.tep.com/role/INCOMETAXESTables 94 false false R95.htm 2488459 - Disclosure - INCOME TAXES (Additional Information) (Details) Sheet http://www.tep.com/role/INCOMETAXESAdditionalInformationDetails INCOME TAXES (Additional Information) (Details) Details http://www.tep.com/role/INCOMETAXESTables 95 false false R96.htm 2489460 - Disclosure - INCOME TAXES (The Significant Components of Deferred Income Tax Assets and Liabilities) (Details) Sheet http://www.tep.com/role/INCOMETAXESTheSignificantComponentsofDeferredIncomeTaxAssetsandLiabilitiesDetails INCOME TAXES (The Significant Components of Deferred Income Tax Assets and Liabilities) (Details) Details http://www.tep.com/role/INCOMETAXESTables 96 false false R97.htm 2490461 - Disclosure - INCOME TAXES (Summary of Tax Carryforwards) (Details) Sheet http://www.tep.com/role/INCOMETAXESSummaryofTaxCarryforwardsDetails INCOME TAXES (Summary of Tax Carryforwards) (Details) Details http://www.tep.com/role/INCOMETAXESTables 97 false false R98.htm 2491462 - Disclosure - INCOME TAXES (Uncertain Tax Positions) (Details) Sheet http://www.tep.com/role/INCOMETAXESUncertainTaxPositionsDetails INCOME TAXES (Uncertain Tax Positions) (Details) Details http://www.tep.com/role/INCOMETAXESTables 98 false false All Reports Book All Reports tep-20211231.htm tep-20211231.xsd tep-20211231_cal.xml tep-20211231_def.xml tep-20211231_lab.xml tep-20211231_pre.xml tepex2312312021.htm tepex2412312021.htm tepex31a12312021.htm tepex31b12312021.htm tepex3212312021.htm http://fasb.org/us-gaap/2021-01-31 http://xbrl.sec.gov/dei/2021q4 true true