REGULATORY MATTERS (Cost Recovery Mechanisms) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Jun. 30, 2013	Mar. 31, 2014
TUCSON ELECTRIC POWER COMPANY
Schedule of Regulatory Cost Recovery Mechanisms [Line Items]
Energy Efficiency Performance Incentive		$ 2
Cap on increase in lost fixed cost recovery rate	1.00%
Regulated Operating Revenue, Other		5
UNS Electric
Schedule of Regulatory Cost Recovery Mechanisms [Line Items]
Regulated Operating Revenue, Other		$ 1