Accounting for Derivative Instruments, Trading Activities and Activities Hedging (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011 GWh GBtu	Jun. 30, 2010	Jun. 30, 2011 GWh GBtu	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010 GWh GBtu
Settlement of forward power purchase and sales contracts that did not result in physical delivery
Forward Power Sales	$ 2	$ 5	$ 3	$ 7
Forward Power Purchases	(3)	(6)	(4)	(7)
Total Sales and Purchases Not Resulting in Physical Delivery	(1)	(1)	(1)
Derivatives with Credit-Risk related Contingent Features
Cash Collateral Posted	1		1			3
Accounting for Derivative Instruments, Trading Activities and Activities Hedging (Textuals) [Abstract]
Liabilities related to cash flow hedges of UniSource Energy and TEP	13		13			12
Net unrealized losses on derivative activities reported in AOCI, after tax	1	2	1	5
Realized losses on settled gas swaps	3	5	9	9
Net realized and unrealized gains and losses other energy contracts	less than $0.1 million	less than $0.1 million	less than $0.1 million	less than $0.1 million
Gas swaps, in GBtu	19,119		19,119			14,973
Power contracts, in GWh	4,051		4,051			4,807
UniSource Energy [Member]
Derivatives with Credit-Risk related Contingent Features
Net Liability Position	65		65
Cash Collateral Posted	1		1
Letters of Credit Outstanding, Amount	12		12
Additional Collateral to Post if Contingent Features Triggered	58		58
UNS ELECTRIC, INC. [Member]
Accounting for Derivative Instruments, Trading Activities and Activities Hedging (Textuals) [Abstract]
Credit exposure to other counterparties related to supply and hedging contracts	3		3
Number of counterparties	1		1
TEP [Member]
Derivatives with Credit-Risk related Contingent Features
Net Liability Position	35		35
Cash Collateral Posted	1		1
Letters of Credit Outstanding, Amount	1		1
Additional Collateral to Post if Contingent Features Triggered	34		34
Accounting for Derivative Instruments, Trading Activities and Activities Hedging (Textuals) [Abstract]
Realized losses on settled gas swaps	2	3	2	3
Derivative assets related to other energy contracts					0
Derivative liabilities related to other energy contracts					0
Gas swaps, in GBtu	10,098		10,098			6,424
Power contracts, in GWh	1,154		1,154			1,144
Credit exposure to other counterparties related to wholesale marketing and gas hedging activities	$ 15		$ 15
Number of counterparties	4		4
Counterparties which are individually composed of total credit exposure greater than	10.00%		10.00%