Fair Value Measurements (Details 2) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
TEP [Member] \| Carrying Value
Liabilities
Long-Term Debt	$ 1,004	$ 1,004
Carrying Value
Assets
TEP Investment in Lease Debt and Equity	66	105
Liabilities
Long-Term Debt	1,371	1,353
TEP [Member] \| Fair Value
Liabilities
Long-Term Debt	917	866
Fair Value
Assets
TEP Investment in Lease Debt and Equity	75	112
Liabilities
Long-Term Debt	1,315	1,243
TEP [Member] \| UNS Gas Senior Unsecured Notes
Fair Value Measurements (Textuals) [Abstract]
Current Maturities of Long-Term Debt	50
Fair Value of the Current Maturities of Long-Term Debt	$ 50.3

Fair Value Measurements.

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Investment In Lease Debt And Equity.

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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Estimated fair value of the debt instrument at the balance-sheet date.

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-Name Statement of Financial Accounting Standard (FAS)
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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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