Monetary amount specified by the derivative(s). Expressed as an absolute value.

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Additional Short Term Borrowings Allowed Under Debt Covenants.

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Debt instruments maturity date.

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Cash inflow associated with amount received from the sale of assets or business to an affiliate.

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Proceeds of Senior guaranteed notes used to payment of notes.

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Repayment Of Borrowings Under Revolving Credit Facility.

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Term Loan Facility Borrowings.

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Term loan facility period.

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The percentage points added to the reference rate to compute the variable rate on the debt instrument.

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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Interest rate stated in the contractual debt agreement.

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Fixed interest rate related to the interest rate derivative.

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Amount borrowed under the credit facility as of the balance sheet date.

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Debt and Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended						1 Months Ended					1 Months Ended
	Aug. 31, 2011	Jul. 25, 2011	Sep. 30, 2011 UniSource Energy [Member]	Dec. 31, 2010 UniSource Energy [Member]	Sep. 30, 2011 TEP [Member]	Dec. 31, 2010 TEP [Member]	Jul. 31, 2011 UED [Member]	Aug. 31, 2011 UNS GAS, INC. [Member]	Aug. 31, 2011 UNS GAS, INC. [Member] Senior guaranteed notes at 5.39%	Aug. 31, 2011 UNS GAS, INC. [Member] Senior guaranteed notes at 6.23%	Aug. 31, 2011 UNS ELECTRIC, INC. [Member]	Aug. 31, 2011 Senior guaranteed notes at 5.39%	Aug. 31, 2011 Senior guaranteed notes at 6.23%
Credit Facilities
Borrowing under revolving credit facility		$ 30	$ 71	$ 27	$ 5	$ 0
Term loan facility borrowings											30
Repayment of borrowings under revolving credit facility											30
Term loan facility period	4 years
Senior guaranteed notes Issued					0							50
Proceeds of senior guaranteed notes used to payment of notes													50
Debt instruments maturity date												2026-08	2011-08
Senior guaranteed notes									5.39%	6.23%
Proceeds from sale of assets or business to affiliate							63
Repay of outstanding secured term loan							27
Interest Rate											1.25%
Fixed rate of interest											0.97%
Derivative notional amount											30
Additional short term borrowings allowed under debt covenants								5			5
Cost Capitalization								$ 0.4