The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

DEBT, CREDIT FACILITIES, AND CAPITAL LEASE OBLIGATIONS (Maturities of Long-term Debt) (Parenthetical) (Detail) (TUCSON ELECTRIC POWER COMPANY, USD $)	Dec. 31, 2013 Variable Rate Demand Obligation [Member]	Dec. 31, 2010 Variable Rate Demand Obligation [Member]	Dec. 31, 2013 Unsecured Debt [Member]	Mar. 31, 2013 Unsecured Debt [Member]	Sep. 30, 2012 Unsecured Debt [Member]	Jun. 30, 2012 Unsecured Debt [Member]	Mar. 31, 2012 Unsecured Debt [Member]
Schedule Of Maturities Of Long Term Debt [Line Items]
Debt instrument, face amount	$ 115,000,000	$ 37,000,000		$ 91,000,000	$ 150,000,000	$ 16,000,000	$ 177,000,000
Debt discount			$ 1,000,000