FAIR VALUE MEASUREMENTS & DERIVATIVE INSTRUMENTS (Energy Contracts Derivative Volumes) (Details)	Mar. 31, 2014 GWh	Dec. 31, 2013 GWh
Power Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	1,901	1,583
Gas Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	45,173,000,000	33,371,000,000
TUCSON ELECTRIC POWER COMPANY | Power Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	896	779
TUCSON ELECTRIC POWER COMPANY | Gas Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	15,821,000,000	9,615,000,000