FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Derivative Volumes) (Details)	Jun. 30, 2014 GWh	Dec. 31, 2013 GWh
Power Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	1,933	1,583
Gas Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	63,546,000,000	33,371,000,000
TUCSON ELECTRIC POWER COMPANY | Power Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	976	779
TUCSON ELECTRIC POWER COMPANY | Gas Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives Volumes	27,176,000,000	9,615,000,000