CONSOLIDATED STATEMENTS OF CAPITALIZATION (USD $) In Thousands, except Share data, unless otherwise specified																	12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Springerville Unit 1 [Member]	Dec. 31, 2011 Springerville Unit 1 [Member]	Dec. 31, 2012 Springerville Coal Handling Facilities [Member]	Dec. 31, 2011 Springerville Coal Handling Facilities [Member]	Dec. 31, 2012 Springerville Common Facilities [Member]	Dec. 31, 2011 Springerville Common Facilities [Member]	Dec. 31, 2012 Tucson Electric Power Company [Member]	Dec. 31, 2011 Tucson Electric Power Company [Member]	Dec. 31, 2012 Tucson Electric Power Company [Member] Springerville Unit 1 [Member]	Dec. 31, 2011 Tucson Electric Power Company [Member] Springerville Unit 1 [Member]	Dec. 31, 2012 Tucson Electric Power Company [Member] Springerville Coal Handling Facilities [Member]	Dec. 31, 2011 Tucson Electric Power Company [Member] Springerville Coal Handling Facilities [Member]	Dec. 31, 2012 Tucson Electric Power Company [Member] Springerville Common Facilities [Member]	Dec. 31, 2011 Tucson Electric Power Company [Member] Springerville Common Facilities [Member]	Dec. 31, 2011 Convertible Senior Notes [Member]	Dec. 31, 2012 Unsecured Fixed Rate Bonds [Member] Tucson Electric Power Company [Member]	Dec. 31, 2011 Unsecured Fixed Rate Bonds [Member] Tucson Electric Power Company [Member]	Dec. 31, 2012 Unsecured Notes [Member] Tucson Electric Power Company [Member]	Dec. 31, 2011 Unsecured Notes [Member] Tucson Electric Power Company [Member]	Dec. 31, 2012 Senior Unsecured Notes [Member] UNS Gas and UNS Electric [Member]	Dec. 31, 2011 Senior Unsecured Notes [Member] UNS Gas and UNS Electric [Member]	Dec. 31, 2012 Credit Agreement [Member]	Dec. 31, 2011 Credit Agreement [Member]	Dec. 31, 2012 Variable Rate Tax-Exempt Bonds [Member] Tucson Electric Power Company [Member]	Dec. 31, 2011 Variable Rate Tax-Exempt Bonds [Member] Tucson Electric Power Company [Member]	Dec. 31, 2012 Unsecured Term Loan [Member] UNS Electric [Member]	Dec. 31, 2011 Unsecured Term Loan [Member] UNS Electric [Member]
COMMON STOCK EQUITY
Common Stock-No Par Value	$ 882,138	$ 725,903							$ 888,971	$ 888,971
Capital Stock Expense									(6,357)	(6,357)
Accumulated Deficit	193,117	172,655							(12,157)	(47,627)
Accumulated Other Comprehensive Loss	(9,790)	(10,084)							(9,530)	(10,044)
Total Common Stock Equity	1,065,465	888,474							860,927	824,943
Maturity date																	2035							2016				2015
PREFERRED STOCK
No Par Value, 1,000,000 Shares Authorized, None Outstanding
CAPITAL LEASE OBLIGATIONS
Capital Lease Obligations	352,721	430,202	196,843	253,481	48,038	65,022	107,840	111,699	352,721	430,202	196,843	253,481	48,038	65,022	107,840	111,699
Less Current Maturities	(90,583)	(77,482)							(90,583)	(77,482)
Total Long-Term Capital Lease Obligations	262,138	352,720							262,138	352,720
LONG-TERM DEBT
Long-Term Debt	1,498,442	1,517,373							1,223,442	1,080,373							150,000	609,320	615,855	398,822	249,218	200,000	200,000	45,000	57,000	215,300	215,300	30,000	30,000
Long-Term Debt	1,498,442	1,517,373							1,223,442	1,080,373							150,000	609,320	615,855	398,822	249,218	200,000	200,000	45,000	57,000	215,300	215,300	30,000	30,000
Long-Term Debt	1,498,442	1,517,373							1,223,442	1,080,373							150,000	609,320	615,855	398,822	249,218	200,000	200,000	45,000	57,000	215,300	215,300	30,000	30,000
Total Capitalization	$ 2,826,045	$ 2,758,567							$ 2,346,507	$ 2,258,036
Shares Authorized	75,000,000	75,000,000							75,000,000	75,000,000
Shares Outstanding	41,343,851	36,918,024							32,139,434	32,139,434
Maturity date, start																		2020		2021		2015				2014
Maturity date, end																		2040		2023		2026				2016
Fixed interest rate of Long-Term Debt																	4.50%
Long-Term Debt, Interest Rate, Minimum																		4.50%		3.85%		5.39%
Long-Term Debt, Interest Rate, Maximum																		6.38%		5.15%		7.10%