EMPLOYEE BENEFIT PLANS (Target Allocation Percentages for Major Categories of Plan Assets) (Detail)	12 Months Ended
	Dec. 31, 2013
TUCSON ELECTRIC POWER COMPANY
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	100.00%
TUCSON ELECTRIC POWER COMPANY | Fixed Income
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	41.00%
TUCSON ELECTRIC POWER COMPANY | United States Large Cap
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	24.00%
TUCSON ELECTRIC POWER COMPANY | Non-United States Developed
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	15.00%
TUCSON ELECTRIC POWER COMPANY | Real Estate
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	8.00%
TUCSON ELECTRIC POWER COMPANY | United States Small Cap
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	5.00%
TUCSON ELECTRIC POWER COMPANY | Non-United States Emerging
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	5.00%
TUCSON ELECTRIC POWER COMPANY | Private Equity
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	2.00%
TUCSON ELECTRIC POWER COMPANY | Cash/Treasury Bills
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	0.00%
UNS Gas and UNS Electric [Member]
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	100.00%
UNS Gas and UNS Electric [Member] | Fixed Income
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	42.00%
UNS Gas and UNS Electric [Member] | United States Large Cap
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	24.00%
UNS Gas and UNS Electric [Member] | Non-United States Developed
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	14.00%
UNS Gas and UNS Electric [Member] | Real Estate
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	10.00%
UNS Gas and UNS Electric [Member] | United States Small Cap
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	5.00%
UNS Gas and UNS Electric [Member] | Non-United States Emerging
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	5.00%
UNS Gas and UNS Electric [Member] | Private Equity
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	0.00%
UNS Gas and UNS Electric [Member] | Cash/Treasury Bills
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	0.00%
VEBA Trust [Member]
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	100.00%
VEBA Trust [Member] | Fixed Income
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	38.00%
VEBA Trust [Member] | United States Large Cap
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	39.00%
VEBA Trust [Member] | Non-United States Developed
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	7.00%
VEBA Trust [Member] | Real Estate
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	0.00%
VEBA Trust [Member] | United States Small Cap
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	5.00%
VEBA Trust [Member] | Non-United States Emerging
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	9.00%
VEBA Trust [Member] | Private Equity
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	0.00%
VEBA Trust [Member] | Cash/Treasury Bills
Pension And Other Employee Benefit Plans [Line Items]
Target allocation percentage of plan assets	2.00%