EMPLOYEE BENEFIT PLANS (Pension and Other Retiree Benefit Related Amounts) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Pension Asset Included in Other Regulatory Assets	$ 75	$ 129
Accrued Benefit Liability Included in Accrued Employee Expenses	(1)	(1)
Accrued Benefit Liability Included in Pension and Other Retiree Benefits	(28)	(90)
Accumulated Other Comprehensive Loss (related to SERP)	2	4
Net Amount Recognized	48	42
Other Retiree Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Pension Asset Included in Other Regulatory Assets	4	10
Accrued Benefit Liability Included in Accrued Employee Expenses	(2)	(2)
Accrued Benefit Liability Included in Pension and Other Retiree Benefits	(63)	(69)
Accumulated Other Comprehensive Loss (related to SERP)	0	0
Net Amount Recognized	(61)	(61)
UNS Gas and UNS Electric [Member] | Pension Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Accrued pension benefit liability	5	9
UNS Gas and UNS Electric [Member] | Other Retiree Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Accrued pension benefit liability	$ 1	$ 1