NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (AFUDC Rates) (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
TUCSON ELECTRIC POWER COMPANY
Long-term Contract for Purchase of Electric Power [Line Items]
Average AFUDC Rate on Regulated Construction Expenditures	7.38%	7.22%	6.72%
UNS Electric
Long-term Contract for Purchase of Electric Power [Line Items]
Average AFUDC Rate on Regulated Construction Expenditures	8.07%	7.89%	8.18%
UNS Gas
Long-term Contract for Purchase of Electric Power [Line Items]
Average AFUDC Rate on Regulated Construction Expenditures	7.89%	7.95%	8.32%