DEBT, CREDIT FACILITIES, AND CAPITAL LEASE OBLIGATIONS (Effect of Fixing Interest Rates on Amortizing Principal Balances of Swaps) (Detail) (Springerville Common Facilities Lease Debt [Member], TUCSON ELECTRIC POWER COMPANY, USD $)	Dec. 31, 2013
Derivative Instruments And Hedging Activities [Line Items]
Derivative basis spread	1.75%
Interest Rate Swap One [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative amount of hedged item	$ 33,000,000
Fixed rate of interest related to interest rate swap	5.77%
Derivative basis spread	1.75%
Interest Rate Swap Two [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative amount of hedged item	16,000,000
Fixed rate of interest related to interest rate swap	3.18%
Derivative basis spread	1.75%
Interest Rate Swap Three [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative amount of hedged item	$ 6,000,000
Fixed rate of interest related to interest rate swap	3.32%
Derivative basis spread	1.75%