EMPLOYEE BENEFIT PLANS (Change in Projected Benefit Obligation and Plan Assets and Reconciliation of Funded Status) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Change in Projected Benefit Obligation
Interest Cost		$ 15
Service Cost	3
Change in Plan Assets
Fair Value Beginning Balance	289
Fair Value Ending Balance	323	289
Pension Benefits [Member]
Change in Projected Benefit Obligation
Benefit Obligation at Beginning of Year	380	319
Actuarial (Gain) Loss	(38)	51
Interest Cost	15	16	15
Service Cost	13	10	10
Benefits Paid	(18)	(15)
Projected Benefit Obligation at End of Year	352	380	319
Change in Plan Assets
Fair Value Beginning Balance	289	245
Actual Return on Plan Assets	29	36
Benefits Paid	(18)	(15)
Employer Contributions	23	23
Fair Value Ending Balance	323	289	245
Funded Status at End of Year	(29)	(91)
Other Retiree Benefits [Member]
Change in Projected Benefit Obligation
Benefit Obligation at Beginning of Year	78	73
Actuarial (Gain) Loss	(5)	3
Interest Cost	3	3	4
Service Cost	4	3	3
Benefits Paid	(4)	(4)
Projected Benefit Obligation at End of Year	75	78	73
Change in Plan Assets
Fair Value Beginning Balance	7	5
Actual Return on Plan Assets	1	1
Benefits Paid	(4)	(4)
Employer Contributions	6	5
Fair Value Ending Balance	10	7	5
Funded Status at End of Year	(65)	(71)
TUCSON ELECTRIC POWER COMPANY | Pension Benefits [Member]
Change in Plan Assets
Employer Contributions	22	20
TUCSON ELECTRIC POWER COMPANY | Other Retiree Benefits [Member]
Change in Plan Assets
Employer Contributions	$ 6	$ 5