Fair Value Measurements (Details 1) (USD $) In Millions	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
Jun. 30, 2010	Jun. 30, 2010	Jun. 30, 2010 TEP [Member] Energy Contracts [Member]	Jun. 30, 2011 TEP [Member] Energy Contracts [Member]	Jun. 30, 2010 TEP [Member] Energy Contracts [Member]	Mar. 31, 2011 TEP [Member] Energy Contracts [Member]	Jun. 30, 2010 Equity Method Investments [Member]	Jun. 30, 2010 Equity Method Investments [Member]	Jun. 30, 2011 Energy Contracts [Member]	Jun. 30, 2010 Energy Contracts [Member]	Jun. 30, 2011 Energy Contracts [Member]	Jun. 30, 2010 Energy Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Beginning Balance	$ (10)	$ (7)	$ (2)	$ 1	$ (4)	$ 1	$ 6	$ 6	$ (11)	$ (16)	$ (10)	$ (13)
Gains and (Losses) (Realized/Unrealized) Recorded to:
Net Regulatory Assets-Derivative Instruments	1	(4)	4	1	7				(1)	1	(3)	(4)
Other Comprehensive Income		(1)		(1)	(1)						(1)	(1)
Other Expense	(5)	(5)					(5)	(5)
Settlements	4	7							3	4	5	7
Ending Balance	(10)	(10)	2	1	2	1	1	1	(9)	(11)	(9)	(11)
Total gains (losses) attributable to the change in change in unrealized gains or losses relating to assets/liabilities still held at the end of the period		$ (4)	$ 4		$ 6				$ (1)		$ (3)	$ (4)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset and liabilities Value.

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- Definition

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss).

+ Details

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- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset other expense.

+ Details

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- Definition

Total Gains Losses Attributable To Change In Change In Unrealized Gains Or Losses Relating.

+ Details

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- Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph c(1)

+ Details

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- Definition

This element represents purchases, sales, issuances, and settlements (net) which have taken place during the period in relation to assets measured at fair value on a recurring basis using unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph c(2)

+ Details

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