Regulation (Narrative) (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended			27 Months Ended				0 Months Ended		4 Months Ended		12 Months Ended		12 Months Ended	0 Months Ended		12 Months Ended	0 Months Ended	12 Months Ended		56 Months Ended	12 Months Ended
	Dec. 09, 2011 Decimals	Nov. 22, 2011	Oct. 05, 2011	Jun. 30, 2010	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011	Nov. 01, 2011	Jul. 02, 2010	Dec. 31, 2008	Sep. 30, 2010 Natural Gas Fired Combustion Turbine Unit mW	Dec. 09, 2011 Solar Power Generation Projects [Member] mW	Oct. 08, 2009 Palo Verde Nuclear Generating Plant	Oct. 08, 2009 New Mexico Jurisdictional Non-Fuel And Purchased Power Base Rate	Dec. 31, 2008 Transmission Agreement Luna Energy Facility	Sep. 30, 2008 Transmission Agreement Luna Energy Facility	Dec. 31, 2011 Renewable Procurement Plan, 2011	Mar. 30, 2011 Maximum	Mar. 30, 2011 Minimum	Dec. 31, 2011 TEP Transmission Agreement, per TEP Claim Maximum Tucson Electric Power Company mW	Dec. 03, 2008 TEP Transmission Agreement, per Judgement Tucson Electric Power Company	Dec. 31, 2008 TEP Transmission Agreement, per Judgement Tucson Electric Power Company Luna Energy Facility	Dec. 31, 2011 TEP Transmission Agreement, per Judgement Maximum Tucson Electric Power Company mW	Sep. 30, 2010 TEP Transmission Agreement, per Settlement Tucson Electric Power Company	Dec. 31, 2011 TEP Transmission Agreement, per Settlement Maximum Tucson Electric Power Company mW	Dec. 31, 2011 Two TEP Transmission Agreements, 2011 Maximum Tucson Electric Power Company mW	Nov. 15, 2011 Revolving Credit Facility Expiring September 2016	Oct. 13, 2011 Revolving Credit Facility Expiring September 2016 NMPRC	Oct. 13, 2011 Revolving Credit Facility Expiring September 2016 FERC	Oct. 13, 2011 Revolving Credit Facility Expiring September 2016 Maximum FERC
Regulation [Line Items]
Annual non-fuel base rate increase											$ 17.15
Customer's percentage of off-system sales margins											90.00%
Retained percentage of off-system sales margins				75.00%							10.00%
Regulatory Noncurrent Asset, Amortization Period								P10Y
Reduction in fixed fuel factor, amount						19.7
Reduction in fixed fuel factor, percent						11.00%
Requested Annual Non-Fuel Base Rate Increase							26.3
Requested Return on Equity							10.60%
Reconcilable Fuel Expense									356.5
Number of Months After The Company Can Seek A Fixed Fuel Factor Revision						4 months
Days Available to City, Determination of Base Rates			185 days
Fuel over and under materiality threshold percentage						4.00%
Energy Efficiency Cost Recovery Factor Recovery					8.3
Military Base Discount Recovery Factor (in percent)						0.936%
Under Recovered Discount Charges						3.9
Electric capacity, MW													87	2.6
Certificate of Convenience and Necessity To Construct Number of Solar Power Gerneration Projects	5
Increase in non-fuel purchased power base rate revenues																5.5
Public Utilities Property Plant and Equipment Estimated Useful life Extension															20 years					60 years	40 years
Imputed Return Rate		2.00%
Percentage Of the Company's Jurisdictional Retail Sales which must be provided with Renewable sources																			10.00%
Line of Credit Facility, Current Borrowing Capacity																													200		200
Line of Credit Facility, Maximum Borrowing Capacity																													300	300	300	300
Return of Refund Related to Dispute																							9.7
Loss contingency reserve																		7.2
Pre-tax charge to earnings																	2.5
Interest paid on refunded balance																								0.9
Transmission capacity, MW																						400			200		170	40
Number of Transmission Capacity Agreements										2
Electrical Transmission Revenue Including Interest																										5.4
Percentage of electrical transmission revenue				25.00%
Electrical Transmission Revenue Shared With Customers				0.7
Counterparty estimate of reimbursement												$ 1.5