COMMITMENTS, CONTINGENCIES, AND ENVIRONMENTAL MATTERS (Commitments Additional Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Unrecorded Unconditional Purchase Obligation [Line Items]
Operating Leases, Rent Expense		$ 3	$ 3	$ 3
TUCSON ELECTRIC POWER COMPANY
Unrecorded Unconditional Purchase Obligation [Line Items]
Duration of Power Purchase Agreement, In Years	20 years
Output Purchase Requirement From Renewable Energy Facility		100.00%
Operating Leases, Rent Expense		$ 2	$ 2	$ 2
UNS Electric
Unrecorded Unconditional Purchase Obligation [Line Items]
Duration of Power Purchase Agreement, In Years	20 years
Output Purchase Requirement From Renewable Energy Facility		100.00%