INCOME TAXES (The Significant Components of Deferred Income Tax Assets and Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Gross Deferred Income Tax Assets
Capital Lease Obligations	$ 127	$ 141
Net Operating Loss Carryforwards	94	72
Customer Advances and Contributions in Aid of Construction	33	34
Alternative Minimum Tax Credit	43	43
Accrued Postretirement Benefits	23	23
Renewable Energy Credit Up-Front Incentive Payments	0	26
Emission Allowance Inventory	10	10
Deferred Tax Assets Unregulated Investment Losses	7	9
Other	50	44
Gross Deferred Income Tax Assets	387	402
Deferred Tax Assets Valuation Allowance	(7)	(7)
Gross Deferred Income Tax Liabilities
Plant - Net	(708)	(648)
Capital Lease Assets - Net	(47)	(34)
Pensions	(21)	(23)
PPFAC	(5)	(6)
Other	(21)	(15)
Deferred Tax Liabilities, Gross	(802)	(726)
Deferred Tax Liabilities, Net	(422)	(331)
TUCSON ELECTRIC POWER COMPANY
Gross Deferred Income Tax Assets
Capital Lease Obligations	127	141
Net Operating Loss Carryforwards	104	85
Customer Advances and Contributions in Aid of Construction	19	19
Alternative Minimum Tax Credit	24	24
Accrued Postretirement Benefits	23	23
Renewable Energy Credit Up-Front Incentive Payments	0	20
Emission Allowance Inventory	10	10
Deferred Tax Assets Unregulated Investment Losses	0	0
Other	44	43
Gross Deferred Income Tax Assets	351	365
Deferred Tax Assets Valuation Allowance	(2)	0
Gross Deferred Income Tax Liabilities
Plant - Net	(615)	(571)
Capital Lease Assets - Net	(47)	(34)
Pensions	(22)	(24)
PPFAC	(2)	(3)
Other	(20)	(15)
Deferred Tax Liabilities, Gross	(706)	(647)
Deferred Tax Liabilities, Net	$ (357)	$ (282)