2.2.0.7 true Comparative Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) 0120 - Statement - Comparative Condensed Consolidated Statements of Cash Flows (Unaudited) true false In Thousands false false 1 USD true false false false UNISOURCE ENERGY CORPORATION dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD true false false false UNISOURCE ENERGY CORPORATION dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ 1 UNISOURCE ENERGY CORPORATION 0 na true na na No definition available. false true false false false false false false false false false http://uns.com/role/statementsofcashflows false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 1 USD true false false false UNISOURCE ENERGY CORPORATION dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD true false false false UNISOURCE ENERGY CORPORATION dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 2 Cash Flows from Operating Activities 2 us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string The net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities include all transactions and events that are not defined as investing or financing activities. Operating activities generally involve producing and delivering goods and providing services. Cash flows from operating activities are generally the cash effects of transactions and other events that enter into the determination of net income. false 3 Cash Receipts from Electric Retail Sales 2 uns_CashReceiptsFromElectricRetailSales uns false debit duration Cash Receipts from Electric Retail Sales. false false false false false false false false false false false verboselabel false 1 true true false false 475942000 475942 false false false 2 true true false false 499791000 499791 false false false xbrli:monetaryItemType monetary Cash Receipts from Electric Retail Sales. No authoritative reference available. false 4 Cash Receipts from Electric Wholesale Sales 2 uns_CashReceiptsFromElectricWholesaleSales uns false debit duration Cash Receipts from Electric Wholesale Sales. false false false false false false false false false false false verboselabel false 1 false true false false 79867000 79867 false false false 2 false true false false 92347000 92347 false false false xbrli:monetaryItemType monetary Cash Receipts from Electric Wholesale Sales. No authoritative reference available. false 5 Cash Receipts from Gas Sales 2 uns_CashReceiptsFromGasSales uns false debit duration Cash Receipts from Gas Sales. false false false false false false false false false false false verboselabel false 1 false true false false 104771000 104771 false false false 2 false true false false 109245000 109245 false false false xbrli:monetaryItemType monetary Cash Receipts from Gas Sales. No authoritative reference available. false 6 Cash Receipts from Operating Springerville Units 3 & 4 2 uns_CashReceiptsFromOperatingSpringervilleUnitsThreeAndFour uns false debit duration Cash Receipts from Operating Springerville Units 3 & 4 false false false false false false false false false false false verboselabel false 1 false true false false 48016000 48016 false false false 2 false true false false 32523000 32523 false false false xbrli:monetaryItemType monetary Cash Receipts from Operating Springerville Units 3 & 4 No authoritative reference available. false 7 Interest Received 2 us-gaap_ProceedsFromInterestReceived us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 5109000 5109 false false false 2 false true false false 6150000 6150 false false false xbrli:monetaryItemType monetary Interest received on loans and other debt instruments during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 8 Income Tax Refunds Received 2 us-gaap_ProceedsFromIncomeTaxRefunds us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false true false false 16924000 16924 false false false xbrli:monetaryItemType monetary The amount of cash received during the period as refunds for the overpayment of taxes. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 29 false 9 Performance Deposits Received 2 us-gaap_ProceedsFromDepositsWithOtherInstitutions us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 6740000 6740 false false false 2 false true false false 15970000 15970 false false false xbrli:monetaryItemType monetary Cash received from refund of deposits with other institutions during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 11 Other Cash Receipts 2 us-gaap_ProceedsFromOtherOperatingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 10841000 10841 false false false 2 false true false false 6754000 6754 false false false xbrli:monetaryItemType monetary Cash received during the current period for operating activities other than those that have been specifically listed above. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 12 Purchased Energy Costs Paid 2 uns_PurchasedEnergyCostsPaid uns false credit duration Purchased Energy Costs Paid. false false false false false false false false false false true negated false 1 false true false false -163922000 -163922 false false false 2 false true false false -165411000 -165411 false false false xbrli:monetaryItemType monetary Purchased Energy Costs Paid. No authoritative reference available. false 13 Fuel Costs Paid 2 uns_FuelCostsPaid uns false credit duration Fuel Costs Paid. false false false false false false false false false false true negated false 1 false true false false -112969000 -112969 false false false 2 false true false false -121318000 -121318 false false false xbrli:monetaryItemType monetary Fuel Costs Paid. No authoritative reference available. false 15 Payment of Other Operations and Maintenance Costs 2 uns_PaymentOfOtherOperationsAndMaintenanceCosts uns false credit duration Payment of Other Operations and Maintenance Costs. false false false false false false false false false false true negated false 1 false true false false -103234000 -103234 false false false 2 false true false false -113975000 -113975 false false false xbrli:monetaryItemType monetary Payment of Other Operations and Maintenance Costs. No authoritative reference available. false 16 Taxes Other Than Income Taxes Paid, Net of Amounts Capitalized 2 us-gaap_PaymentsForOtherTaxes us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -79850000 -79850 false false false 2 false true false false -78321000 -78321 false false false xbrli:monetaryItemType monetary The amount of cash paid during the current period for taxes other than income taxes. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 23 -Subparagraph c false 17 Wages Paid, Net of Amounts Capitalized 2 us-gaap_PaymentsToEmployees us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -63382000 -63382 false false false 2 false true false false -64073000 -64073 false false false xbrli:monetaryItemType monetary Payments of cash to employees, including wages and salaries, during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 18 Interest Paid, Net of Amounts Capitalized 2 us-gaap_InterestPaidNet us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -28851000 -28851 false false false 2 false true false false -26967000 -26967 false false false xbrli:monetaryItemType monetary The amount of cash paid during the current period for interest owed on money borrowed, net of interest capitalized. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 29 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 -Subparagraph e false 19 Capital Lease Interest Paid 2 uns_CapitalLeaseInterestPaid uns false credit duration Capital Lease Interest Paid. false false false false false false false false false false true negated false 1 false true false false -25111000 -25111 false false false 2 false true false false -23802000 -23802 false false false xbrli:monetaryItemType monetary Capital Lease Interest Paid. No authoritative reference available. false 20 Performance Deposit Payments 2 us-gaap_PaymentsForDepositsWithOtherInstitutions us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -6840000 -6840 false false false 2 false true false false -15750000 -15750 false false false xbrli:monetaryItemType monetary Cash paid to make deposits at other institutions during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 21 Income Taxes Paid 2 us-gaap_IncomeTaxesPaid us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -2228000 -2228 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 29 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 -Subparagraph f false 22 Excess Tax Benefit from Stock Options Exercised 2 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -826000 -826 false false false 2 false true false false -469000 -469 false false false xbrli:monetaryItemType monetary Reductions in the entity's income taxes that arise when compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return exceeds compensation cost from share-based compensation recognized in financial statements. This element reduces net cash provided by operating activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A96 false 23 Other Cash Payments 2 us-gaap_PaymentsForOtherOperatingActivities us-gaap true credit duration No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -3167000 -3167 false false false 2 false true false false -3943000 -3943 false false false xbrli:monetaryItemType monetary Cash payments made during the current period for operating activities other than those that have been specifically listed above. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 true 24 Net Cash Flows - Operating Activities 2 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 140906000 140906 false false false 2 false true false false 165675000 165675 false false false xbrli:monetaryItemType monetary The net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities generally involve producing and delivering goods and providing services. Operating activity cash flows include transactions, adjustments, and changes in value that are not defined as investing or financing activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 true 25 Cash Flows from Investing Activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 26 Capital Expenditures 2 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -128579000 -128579 false false false 2 false true false false -177255000 -177255 false false false xbrli:monetaryItemType monetary The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph c false 27 Purchase of Sundt Unit 4 Lease Asset 2 us-gaap_PaymentsToAcquireOtherProductiveAssets us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -51389000 -51389 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The cash outflow for acquisition of or capital improvements on other tangible or intangible assets not otherwise defined in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph c false 28 Prepayment Deposit on UED Debt 2 uns_PrepaymentDepositOnUedDebt uns false credit duration Prepayment Deposit on UED Debt. false false false false false false false false false false true negated false 1 false true false false -1530000 -1530 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Prepayment Deposit on UED Debt. No authoritative reference available. false 29 Purchase of Springerville Lease Debt 2 us-gaap_PaymentsToAcquireHeldToMaturitySecurities us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 false false false 2 false true false false -31375000 -31375 false false false xbrli:monetaryItemType monetary The cash outflow to acquire a debt financial instrument for which the entity has the ability and intent to hold until maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph a false 30 Return of Investment in Springerville Lease Debt 2 us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 21667000 21667 false false false 2 false true false false 906000 906 false false false xbrli:monetaryItemType monetary The cash inflow associated with the maturity, prepayments and calls (requests for early payments) of debt securities designated as held-to-maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 16 -Subparagraph a false 31 Return of Investment from Millennium Energy Businesses 2 us-gaap_ProceedsFromSaleOfOtherInvestments us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 423000 423 false false false 2 false true false false 5000000 5000 false false false xbrli:monetaryItemType monetary The cash inflow associated with the sale of other investments not otherwise defined in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 31 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 16 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 18 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 false 32 Insurance Proceeds for Replacement Assets 2 us-gaap_ProceedsFromInsuranceSettlementInvestingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false true false false 4279000 4279 false false false xbrli:monetaryItemType monetary The cash inflow from the amounts received by the insured under the terms of an insurance contract settlement. This element pertains only to insurance proceeds related to investments, for example fixed assets. It excludes insurance settlements classified as operating cash flows. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 22 -Subparagraph c false 33 Other Cash Receipts 2 uns_OtherCashReceiptsInvestingActivities uns false debit duration Other Cash Receipts. false false false false false false false false false false false verboselabel false 1 false true false false 356000 356 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Other Cash Receipts. No authoritative reference available. false 34 Other Cash Payments 2 us-gaap_PaymentsForProceedsFromOtherInvestingActivities us-gaap true credit duration No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -461000 -461 false false false 2 false true false false -973000 -973 false false false xbrli:monetaryItemType monetary The net cash outflow (inflow) from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 true 35 Net Cash Flows - Investing Activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false -159513000 -159513 false false false 2 false true false false -199418000 -199418 false false false xbrli:monetaryItemType monetary The net cash inflow (outflow) from investing activity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 true 36 Cash Flows from Financing Activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 37 Proceeds from Borrowings Under Revolving Credit Facilities 2 us-gaap_ProceedsFromLinesOfCredit us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 163000000 163000 false false false 2 false true false false 96000000 96000 false false false xbrli:monetaryItemType monetary The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity that is collateralized (backed by pledge, mortgage or other lien in the entity's assets). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 38 Proceeds from Issuance of Long-Term Debt 2 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 39570000 39570 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 39 Proceeds from Stock Options Exercised 2 us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false 5091000 5091 false false false 2 false true false false 988000 988 false false false xbrli:monetaryItemType monetary Value stock issued during the period as a result of the exercise of stock options. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 false 40 Excess Tax Benefit from Stock Options Exercised 2 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 826000 826 false false false 2 false true false false 469000 469 false false false xbrli:monetaryItemType monetary Reductions in the entity's income taxes that arise when compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return exceeds compensation cost from share-based compensation recognized in financial statements. This element represents the cash inflow reported in the enterprise's financing activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph i Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 00-15 -Paragraph 3 false 41 Other Cash Receipts 2 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 4211000 4211 false false false 2 false true false false 3768000 3768 false false false xbrli:monetaryItemType monetary The net cash inflow (outflow) from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18, 19, 20 false 42 Proceeds from Issuance of Short-Term Debt 2 us-gaap_ProceedsFromShortTermDebt us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false true false false 30000000 30000 false false false xbrli:monetaryItemType monetary The cash inflow from a borrowing having initial term of repayment within one year or the normal operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 44 Repayments of Borrowings Under Revolving Credit Facilities 2 us-gaap_RepaymentsOfLinesOfCredit us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -116000000 -116000 false false false 2 false true false false -60000000 -60000 false false false xbrli:monetaryItemType monetary The cash outflow to pay off an obligation from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph b false 45 Payments of Capital Lease Obligations 2 us-gaap_RepaymentsOfLongTermCapitalLeaseObligations us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -44905000 -44905 false false false 2 false true false false -14495000 -14495 false false false xbrli:monetaryItemType monetary The cash outflow for the obligation for lease meeting the criteria for capitalization (with maturities exceeding one year or beyond the operating cycle of the entity, if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26, 31 false 46 Common Stock Dividends Paid 2 us-gaap_PaymentsOfDividendsCommonStock us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -28138000 -28138 false false false 2 false true false false -20664000 -20664 false false false xbrli:monetaryItemType monetary The cash outflow from the distribution of an entity's earnings in the form of dividends to common shareholders. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph a false 47 Repayment of Long-Term Debt 2 us-gaap_RepaymentsOfLongTermDebt us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -17945000 -17945 false false false 2 false true false false -3000000 -3000 false false false xbrli:monetaryItemType monetary The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph b false 48 Payment of Debt Issue/Retirement Costs 2 us-gaap_PaymentsOfFinancingCosts us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -1955000 -1955 false false false 2 false true false false -950000 -950 false false false xbrli:monetaryItemType monetary The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18, 19, 20 false 49 Other Cash Payments 2 uns_OtherCashPaymentsFinancingActivities uns false credit duration Other Cash Payments. false false false false false false false false false false true negatedtotal false 1 false true false false -661000 -661 false false false 2 false true false false -675000 -675 false false false xbrli:monetaryItemType monetary Other Cash Payments. No authoritative reference available. true 50 Net Cash Flows - Financing Activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 3094000 3094 false false false 2 false true false false 31441000 31441 false false false xbrli:monetaryItemType monetary The net cash inflow (outflow) from financing activity for the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 true 51 Net Decrease in Cash and Cash Equivalents 2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false -15513000 -15513 false false false 2 false true false false -2302000 -2302 false false false xbrli:monetaryItemType monetary The net change between the beginning and ending balance of cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 false 52 Cash and Cash Equivalents, Beginning of Year 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant No definition available. false false false false false false false false true false false periodstartlabel false 1 false true false false 76922000 76922 false false false 2 false true false false 55172000 55172 false false false xbrli:monetaryItemType monetary Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 false 53 Cash and Cash Equivalents, End of Period 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant No definition available. false false false false false false false false false true false periodendlabel false 1 false true false false 61409000 61409 false false false 2 false true false false 52870000 52870 false false false xbrli:monetaryItemType monetary Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 false 54 TUCSON ELECTRIC POWER COMPANY 0 na true na na No definition available. false true false false false false false false false false false http://uns.com/role/statementsofcashflows false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 3 USD true false false false TUCSON ELECTRIC POWER COMPANY dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false TUCSON ELECTRIC POWER COMPANY dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 55 Cash Flows from Operating Activities 2 us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string The net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities include all transactions and events that are not defined as investing or financing activities. Operating activities generally involve producing and delivering goods and providing services. Cash flows from operating activities are generally the cash effects of transactions and other events that enter into the determination of net income. false 56 Cash Receipts from Electric Retail Sales 2 uns_CashReceiptsFromElectricRetailSales uns false debit duration Cash Receipts from Electric Retail Sales. false false false false false false false false false false false verboselabel false 1 false true false false 392196000 392196 false false false 2 false true false false 398128000 398128 false false false xbrli:monetaryItemType monetary Cash Receipts from Electric Retail Sales. No authoritative reference available. false 57 Cash Receipts from Electric Wholesale Sales 2 uns_CashReceiptsFromElectricWholesaleSales uns false debit duration Cash Receipts from Electric Wholesale Sales. false false false false false false false false false false false verboselabel false 1 false true false false 87956000 87956 false false false 2 false true false false 99228000 99228 false false false xbrli:monetaryItemType monetary Cash Receipts from Electric Wholesale Sales. No authoritative reference available. false 59 Cash Receipts from Operating Springerville Units 3 & 4 2 uns_CashReceiptsFromOperatingSpringervilleUnitsThreeAndFour uns false debit duration Cash Receipts from Operating Springerville Units 3 & 4 false false false false false false false false false false false verboselabel false 1 false true false false 48016000 48016 false false false 2 false true false false 32523000 32523 false false false xbrli:monetaryItemType monetary Cash Receipts from Operating Springerville Units 3 & 4 No authoritative reference available. false 60 Interest Received 2 us-gaap_ProceedsFromInterestReceived us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 5094000 5094 false false false 2 false true false false 5926000 5926 false false false xbrli:monetaryItemType monetary Interest received on loans and other debt instruments during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 61 Income Tax Refunds Received 2 us-gaap_ProceedsFromIncomeTaxRefunds us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 3369000 3369 false false false 2 false true false false 10423000 10423 false false false xbrli:monetaryItemType monetary The amount of cash received during the period as refunds for the overpayment of taxes. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 29 false 62 Performance Deposits Received 2 us-gaap_ProceedsFromDepositsWithOtherInstitutions us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 1540000 1540 false false false 2 false true false false 1500000 1500 false false false xbrli:monetaryItemType monetary Cash received from refund of deposits with other institutions during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 63 Reimbursement of Affiliate Charges 2 uns_ReimbursementOfAffiliateCharges uns false debit duration Reimbursement of Affiliate Charges. false false false false false false false false false false false verboselabel false 1 false true false false 10210000 10210 false false false 2 false true false false 10993000 10993 false false false xbrli:monetaryItemType monetary Reimbursement of Affiliate Charges. No authoritative reference available. false 64 Other Cash Receipts 2 us-gaap_ProceedsFromOtherOperatingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 4420000 4420 false false false 2 false true false false 3899000 3899 false false false xbrli:monetaryItemType monetary Cash received during the current period for operating activities other than those that have been specifically listed above. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 66 Fuel Costs Paid 2 uns_FuelCostsPaid uns false credit duration Fuel Costs Paid. false false false false false false false false false false true negated false 1 false true false false -108820000 -108820 false false false 2 false true false false -114181000 -114181 false false false xbrli:monetaryItemType monetary Fuel Costs Paid. No authoritative reference available. false 67 Purchased Power Costs Paid 2 uns_PurchasedPowerCostsPaid uns false credit duration Purchased Power Costs Paid. false false false false false false false false false false true negated false 1 false true false false -62297000 -62297 false false false 2 false true false false -73459000 -73459 false false false xbrli:monetaryItemType monetary Purchased Power Costs Paid. No authoritative reference available. false 68 Payment of Other Operations and Maintenance Costs 2 uns_PaymentOfOtherOperationsAndMaintenanceCosts uns false credit duration Payment of Other Operations and Maintenance Costs. false false false false false false false false false false true negated false 1 false true false false -97501000 -97501 false false false 2 false true false false -109853000 -109853 false false false xbrli:monetaryItemType monetary Payment of Other Operations and Maintenance Costs. No authoritative reference available. false 69 Taxes Other Than Income Taxes Paid, Net of Amounts Capitalized 2 us-gaap_PaymentsForOtherTaxes us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -59033000 -59033 false false false 2 false true false false -55617000 -55617 false false false xbrli:monetaryItemType monetary The amount of cash paid during the current period for taxes other than income taxes. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 23 -Subparagraph c false 70 Wages Paid, Net of Amounts Capitalized 2 us-gaap_PaymentsToEmployees us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -51163000 -51163 false false false 2 false true false false -50926000 -50926 false false false xbrli:monetaryItemType monetary Payments of cash to employees, including wages and salaries, during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 71 Interest Paid, Net of Amounts Capitalized 2 us-gaap_InterestPaidNet us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -18299000 -18299 false false false 2 false true false false -16154000 -16154 false false false xbrli:monetaryItemType monetary The amount of cash paid during the current period for interest owed on money borrowed, net of interest capitalized. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 29 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 -Subparagraph e false 72 Capital Lease Interest Paid 2 uns_CapitalLeaseInterestPaid uns false credit duration Capital Lease Interest Paid. false false false false false false false false false false true negated false 1 false true false false -25106000 -25106 false false false 2 false true false false -23796000 -23796 false false false xbrli:monetaryItemType monetary Capital Lease Interest Paid. No authoritative reference available. false 73 Performance Deposit Payments 2 us-gaap_PaymentsForDepositsWithOtherInstitutions us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -1540000 -1540 false false false 2 false true false false -10750000 -10750 false false false xbrli:monetaryItemType monetary Cash paid to make deposits at other institutions during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 false 74 Income Taxes Paid 2 us-gaap_IncomeTaxesPaid us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -1828000 -1828 false false false 2 false true false false -4059000 -4059 false false false xbrli:monetaryItemType monetary The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 29 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 -Subparagraph f false 76 Other Cash Payments 2 us-gaap_PaymentsForOtherOperatingActivities us-gaap true credit duration No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -1561000 -1561 false false false 2 false true false false -2213000 -2213 false false false xbrli:monetaryItemType monetary Cash payments made during the current period for operating activities other than those that have been specifically listed above. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 27 true 77 Net Cash Flows - Operating Activities 2 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 125653000 125653 false false false 2 false true false false 101612000 101612 false false false xbrli:monetaryItemType monetary The net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities generally involve producing and delivering goods and providing services. Operating activity cash flows include transactions, adjustments, and changes in value that are not defined as investing or financing activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 true 78 Cash Flows from Investing Activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 79 Capital Expenditures 2 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -109026000 -109026 false false false 2 false true false false -151367000 -151367 false false false xbrli:monetaryItemType monetary The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph c false 80 Purchase of Sundt Unit 4 Lease Asset 2 us-gaap_PaymentsToAcquireOtherProductiveAssets us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -51389000 -51389 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The cash outflow for acquisition of or capital improvements on other tangible or intangible assets not otherwise defined in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph c false 82 Purchase of Springerville Lease Debt 2 us-gaap_PaymentsToAcquireHeldToMaturitySecurities us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 false false false 2 false true false false -31375000 -31375 false false false xbrli:monetaryItemType monetary The cash outflow to acquire a debt financial instrument for which the entity has the ability and intent to hold until maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph a false 83 Return of Investment in Springerville Lease Debt 2 us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 21667000 21667 false false false 2 false true false false 906000 906 false false false xbrli:monetaryItemType monetary The cash inflow associated with the maturity, prepayments and calls (requests for early payments) of debt securities designated as held-to-maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 16 -Subparagraph a false 85 Insurance Proceeds for Replacement Assets 2 us-gaap_ProceedsFromInsuranceSettlementInvestingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false true false false 4279000 4279 false false false xbrli:monetaryItemType monetary The cash inflow from the amounts received by the insured under the terms of an insurance contract settlement. This element pertains only to insurance proceeds related to investments, for example fixed assets. It excludes insurance settlements classified as operating cash flows. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 22 -Subparagraph c false 86 Other Cash Receipts 2 uns_OtherCashReceiptsInvestingActivities uns false debit duration Other Cash Receipts. false false false false false false false false false false false verboselabel false 1 false true false false 347000 347 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Other Cash Receipts. No authoritative reference available. false 87 Other Cash Payments 2 us-gaap_PaymentsForProceedsFromOtherInvestingActivities us-gaap true credit duration No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -1000 -1 false false false 2 false true false false -407000 -407 false false false xbrli:monetaryItemType monetary The net cash outflow (inflow) from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 true 88 Net Cash Flows - Investing Activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false -138402000 -138402 false false false 2 false true false false -177964000 -177964 false false false xbrli:monetaryItemType monetary The net cash inflow (outflow) from investing activity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 true 89 Cash Flows from Financing Activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 90 Proceeds from Borrowings Under Revolving Credit Facilities 2 us-gaap_ProceedsFromLinesOfCredit us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 110000000 110000 false false false 2 false true false false 73000000 73000 false false false xbrli:monetaryItemType monetary The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity that is collateralized (backed by pledge, mortgage or other lien in the entity's assets). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 91 Proceeds from Issuance of Long-Term Debt 2 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 30000000 30000 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 94 Other Cash Receipts 2 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 400000 400 false false false 2 false true false false 2186000 2186 false false false xbrli:monetaryItemType monetary The net cash inflow (outflow) from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18, 19, 20 false 96 Equity Investment from UniSource Energy 2 us-gaap_ProceedsFromContributionsFromParent us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 15000000 15000 false false false 2 false true false false 30000000 30000 false false false xbrli:monetaryItemType monetary The cash inflow from parent as a source of financing that is recorded as additional paid in capital. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 false 97 Repayments of Borrowings Under Revolving Credit Facilities 2 us-gaap_RepaymentsOfLinesOfCredit us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -100000000 -100000 false false false 2 false true false false -43000000 -43000 false false false xbrli:monetaryItemType monetary The cash outflow to pay off an obligation from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph b false 98 Payments of Capital Lease Obligations 2 us-gaap_RepaymentsOfLongTermCapitalLeaseObligations us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -44851000 -44851 false false false 2 false true false false -14447000 -14447 false false false xbrli:monetaryItemType monetary The cash outflow for the obligation for lease meeting the criteria for capitalization (with maturities exceeding one year or beyond the operating cycle of the entity, if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26, 31 false 101 Payment of Debt Issue/Retirement Costs 2 us-gaap_PaymentsOfFinancingCosts us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -1361000 -1361 false false false 2 false true false false -13000 -13 false false false xbrli:monetaryItemType monetary The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18, 19, 20 false 102 Other Cash Payments 2 uns_OtherCashPaymentsFinancingActivities uns false credit duration Other Cash Payments. false false false false false false false false false false true negatedtotal false 1 false true false false -202000 -202 false false false 2 false true false false -279000 -279 false false false xbrli:monetaryItemType monetary Other Cash Payments. No authoritative reference available. true 103 Net Cash Flows - Financing Activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 8986000 8986 false false false 2 false true false false 47447000 47447 false false false xbrli:monetaryItemType monetary The net cash inflow (outflow) from financing activity for the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 true 104 Net Decrease in Cash and Cash Equivalents 2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false -3763000 -3763 false false false 2 false true false false -28905000 -28905 false false false xbrli:monetaryItemType monetary The net change between the beginning and ending balance of cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 false 105 Cash and Cash Equivalents, Beginning of Year 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant No definition available. false false false false false false false false true false false periodstartlabel false 1 false true false false 22418000 22418 false false false 2 false true false false 33275000 33275 false false false xbrli:monetaryItemType monetary Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 false 106 Cash and Cash Equivalents, End of Period 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant No definition available. false false false false false false false false false true false periodendlabel false 1 true true false false 18655000 18655 false false false 2 true true false false 4370000 4370 false false false xbrli:monetaryItemType monetary Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 false 2 93 false Thousands UnKnown UnKnown false true