DEBT, CREDIT FACILITIES, AND CAPITAL LEASE OBLIGATIONS (Debt) (Detail) (USD $)	6 Months Ended						1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 TUCSON ELECTRIC POWER COMPANY	Jun. 30, 2013 TUCSON ELECTRIC POWER COMPANY	Mar. 31, 2014 TUCSON ELECTRIC POWER COMPANY Unsecured Debt [Member]	Mar. 31, 2013 TUCSON ELECTRIC POWER COMPANY Unsecured Debt [Member]	Mar. 31, 2014 Revolving Credit Facility [Member] TUCSON ELECTRIC POWER COMPANY	Jun. 30, 2014 Revolving Credit Facility [Member] TUCSON ELECTRIC POWER COMPANY	Jun. 30, 2014 Letter of Credit [Member] TUCSON ELECTRIC POWER COMPANY	Jul. 18, 2014 Subsequent Event [Member] Revolving Credit Facility [Member] TUCSON ELECTRIC POWER COMPANY
Debt Instrument [Line Items]
Debt instrument, face amount					$ 150,000,000	$ 91,000,000
Fixed interest rate of long-term debt					5.00%
Repayment of outstanding credit facility	129,000,000	48,000,000	105,000,000	48,000,000			90,000,000
Line of Credit Facility, Maximum Borrowing Capacity								200,000,000	82,000,000
Line of Credit Facility, Remaining Borrowing Capacity								184,000,000		134,000,000
Guaranty Liabilities									15,000,000
Letters of Credit Outstanding, Amount									$ 15,000,000