Commitments Contingencies and Proposed Environmental Matters (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended					1 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2011 MWh GWh GBtu	Jun. 30, 2011 TEP [Member] Coal [Member]	Jun. 30, 2011 TEP [Member] Purchased Power [Member]	Jun. 30, 2011 TEP [Member] Solar Equipment [Member]	Jun. 30, 2011 UNS ELECTRIC, INC. [Member]	Dec. 31, 2008 TEP [Member]	Jun. 30, 2011 TEP [Member]	Jun. 30, 2011 TEP [Member]	Dec. 31, 2010 TEP [Member]	Nov. 30, 2011 UniSource Energy [Member]	Jun. 30, 2011 UniSource Energy [Member]
Long term purchase commitments
Long Term Purchase Commitments Due within one year		$ 34	$ 1	$ 11			$ 46	$ 46
Long Term Purchase Commitments Due within second year		40	5	11			56	56
Long Term Purchase Commitments Due within third year		14	1	11			26	26
Long Term Purchase Commitments Due within fourth year		14	1				15	15
Long Term Purchase Commitments Due within fifth year			1				1	1
Long Term Purchase Commitments Due After fifth year			10				10	10
Long Term Purchase Commitments Total		102	19	33			154	154
Commitments and Contingencies (Textuals) [Abstract]
Commitment to purchase photovoltaic equipment having capacity	9
Minimum payments for forward purchases due in 2012					6
Obligation to purchase under renewable energy PPA								100% of the output of one renewable energy generation facility through 2031
Maximum committed payments under design-build contract for construction project										53
Remaining committed payments under design build contract for construction project											12
Committed payments for tenant improvements											5
Amount refunded by El Paso for transmission service to TEP						11
Unrecognized income related to refund pending resolution of the dispute							11	11
Reduced TEP's rights for transmission under the Exchange Agreement	from 200 MW to 170 MW
Transmission for the amount	30
New firm transmission capacity	40
Settlement amount to be paid by TEP to El Paso under Exchange Agreement								5
Additional transmission expenses TEP would be allowed to recover from retail customers under the PPFAC mechanism							10	12
Term of purchase agreement with Macho Springs facility								P20Y
Pre tax gain to be recognized if settlement agreements are approved by FERC							8	8
TEP's share of the reclamation costs at the expiration dates of coal supply agreement								26
Additional transmission expenses allowed to recover from customers under PPFC mechanism							2
TEP's recorded obligation for final mine reclamation costs							12	12	11
DC lawsuit seeking damages								600
DC lawsuit seeking punative damages								Not less than 1 billion
Percentage of ownership of San Juan units 1 and 2	50.00%							7.50%
Percentage of ownership in total generation capacity	20.00%
Approximate Mileage of Transmission line from Tucson to Nogales	60
Transmission line approved by ACC, in KV	345
TEP Capitalized Amount related to Nogales transmission line project							11	11	11
Land and Land Rights Related to Nogales Transmission Line									2
Estimated Capital cost for mercury emission control equipment for Springerville Units 1 and 2	5
Estimated Annual Operating Expenses for mercury emission control equipment for Springerville Units 1 and 2	3
TEP's share of capital expenditures related to installation of SCRs AtSJ								155
Capital expenditure related to installation of SNCR at AtSJ								17
TEP's Share of the Estimated Capital Cost for Mercury Control Equipment for Navajo	Less than 1 million
TEP's Estimated share of capital expenditure related to installation of SCRs for units 4 and 5								35
TEP's estimated capital cost if SCR is required at Navajo								42
TEP's capital expenditure related to installation of baghouses at Navajo								$ 43