EMPLOYEE BENEFIT PLANS (Pension Plan Asset Allocations) (Detail)	Dec. 31, 2013	Dec. 31, 2012
TUCSON ELECTRIC POWER COMPANY
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	100.00%	100.00%
TUCSON ELECTRIC POWER COMPANY | Equity Securities
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	50.00%	50.00%
TUCSON ELECTRIC POWER COMPANY | Fixed Income
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	40.00%	41.00%
TUCSON ELECTRIC POWER COMPANY | Real Estate
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	7.00%	7.00%
TUCSON ELECTRIC POWER COMPANY | Other
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	3.00%	2.00%
UNS Gas and UNS Electric [Member]
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	100.00%	100.00%
UNS Gas and UNS Electric [Member] | Equity Securities
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	50.00%	56.00%
UNS Gas and UNS Electric [Member] | Fixed Income
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	40.00%	33.00%
UNS Gas and UNS Electric [Member] | Real Estate
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	10.00%	11.00%
UNS Gas and UNS Electric [Member] | Other
Pension And Other Employee Benefit Plans [Line Items]
Pension plan assets allocation	0.00%	0.00%