SUPPLEMENTAL CASH FLOW INFORMATION SUPPLEMENTAL CASH FLOW INFORMATION - Non-Cash Transactions (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		3 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2012 TUCSON ELECTRIC POWER COMPANY	Oct. 31, 2013 Springerville Unit One Lease [Member] TUCSON ELECTRIC POWER COMPANY	Sep. 30, 2013 Springerville Unit One Lease [Member] TUCSON ELECTRIC POWER COMPANY	Sep. 30, 2013 Springerville Unit One Lease [Member] TUCSON ELECTRIC POWER COMPANY	Mar. 31, 2013 Unsecured Tax Exempt Bonds [Member] TUCSON ELECTRIC POWER COMPANY	Sep. 30, 2012 Unsecured Tax Exempt Bonds [Member] TUCSON ELECTRIC POWER COMPANY	Sep. 30, 2012 Convertible Senior Notes [Member] UNS Energy Corporation [Member]
Increase in Capital Lease Obligation		$ 55	$ 39	$ 39
Increase in Utility Plant under Capital Lease		55	39	39
Debt Instrument, Face Amount					91	193
Dividends	30
Debt Conversion, Converted Instrument, Amount							147
Debt Conversion, Original Debt, Amount							$ 150