FAIR VALUE MEASUREMENTS & DERIVATIVE INSTRUMENTS (Financial Impact of Energy Contracts) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Increase (Decrease) to Regulatory Assets/Liabilities	$ (9)	$ (21)	$ 2
TUCSON ELECTRIC POWER COMPANY
Derivative Instruments, Gain (Loss) [Line Items]
Increase (Decrease) to Regulatory Assets/Liabilities	$ 0	$ (6)	$ 2