FAIR VALUE MEASUREMENTS & DERIVATIVE INSTRUMENTS (Balance Sheets Carrying Value Estimated Fair Values of Financial Instruments) (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Liabilities:
Long-Term Debt	$ 1,507,070,000	$ 1,498,442,000
TUCSON ELECTRIC POWER COMPANY
Liabilities:
Long-Term Debt	1,223,070,000
Carrying Value [Member] | Level 2 [Member]
Liabilities:
Long-Term Debt	1,507,000,000	1,498,000,000
Carrying Value [Member] | Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets:
TEP Investment in Lease Debt	0	9,000,000
Liabilities:
Long-Term Debt	1,223,000,000	1,223,000,000
Carrying Value [Member] | Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets:
TEP Investment in Lease Equity	36,000,000	36,000,000
Fair Value [Member] | Level 2 [Member]
Liabilities:
Long-Term Debt	1,521,000,000	1,583,000,000
Fair Value [Member] | Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets:
TEP Investment in Lease Debt	0	9,000,000
Liabilities:
Long-Term Debt	1,214,000,000	1,271,000,000
Fair Value [Member] | Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets:
TEP Investment in Lease Equity	$ 25,000,000	$ 23,000,000