Fair Value Measurements (Details 1) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Beginning Balance		$ (10)		$ (7)
Gains and (Losses) Realized/Unrealized Recorded to:
Net Regulatory Assets-Derivative Instruments	1	(6)		(10)
Other Comprehensive Income		(1)		(3)
Other Expense		0		(5)
Settlements		4		12
Ending Balance		(13)		(13)
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		(6)		(7)
TEP [Member] | Energy Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Beginning Balance	1	2	1	(4)
Gains and (Losses) Realized/Unrealized Recorded to:
Net Regulatory Assets-Derivative Instruments		2	2	10
Other Comprehensive Income		(1)	(1)	(3)
Other Expense		0		0
Settlements	(1)	(1)	(1)	(1)
Ending Balance	1	2	1	2
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	1	1	1	6
Equity Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Beginning Balance		1		6
Gains and (Losses) Realized/Unrealized Recorded to:
Net Regulatory Assets-Derivative Instruments		0		0
Other Comprehensive Income		0		0
Other Expense		0		(5)
Settlements		0		0
Ending Balance		1		1
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		0		0
Energy Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Beginning Balance	(9)	(11)	(10)	(13)
Gains and (Losses) Realized/Unrealized Recorded to:
Net Regulatory Assets-Derivative Instruments	(3)	(6)	(6)	(10)
Other Comprehensive Income		(1)	(1)	(3)
Other Expense		0		0
Settlements	2	4	7	12
Ending Balance	(10)	(14)	(10)	(14)
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	$ (3)	$ (6)	$ (6)	$ (7)