FAIR VALUE MEASUREMENTS & DERIVATIVE INSTRUMENTS (Carrying Value and Estimated Fair Values of Financial Instruments) (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Liabilities:
Long-Term Debt	$ 1,659,278,000	$ 1,507,070,000
TUCSON ELECTRIC POWER COMPANY
Liabilities:
Long-Term Debt	1,372,278,000	1,223,070,000
Carrying Value [Member] | Level 2 [Member]
Liabilities:
Long-Term Debt	1,659,000,000	1,507,000,000
Carrying Value [Member] | Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY
Liabilities:
Long-Term Debt	1,372,000,000	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	1,722,000,000	1,521,000,000
Fair Value [Member] | Level 2 [Member] | TUCSON ELECTRIC POWER COMPANY
Liabilities:
Long-Term Debt	1,407,000,000	1,214,000,000
Fair Value [Member] | Level 3 [Member] | TUCSON ELECTRIC POWER COMPANY
Assets:
TEP Investment in Lease Equity	$ 25,000,000	$ 25,000,000