Debt and Credit Facilities (Details) (USD $) In Millions						1 Months Ended
Jun. 30, 2011 UniSource Energy [Member]	Dec. 31, 2010 UniSource Energy [Member]	Aug. 31, 2011 TEP [Member]	Jun. 30, 2011 TEP [Member]	Jul. 25, 2011 UNS Electric Resolver [Member]	Jul. 31, 2011 UED [Member]
Credit Facilities [Abstract]
Borrowing under revolving credit facility	$ 67	$ 27	$ 0	$ 50	$ 30
Proceeds from Sale of Assets or Business to Affiliate						63
Repayments of Secured Debt						$ 27

Cash inflow associated with amount received from the sale of assets or business to an affiliate.

Name:	uns_ProceedsFromSaleOfAssetsOrBusinessToAffiliate
Namespace Prefix:	uns
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LineOfCreditFacilityAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount borrowed under the credit facility as of the balance-sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityAmountOutstanding
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow from the payment of collateralized debt obligation (backed by pledge, mortgage or other lien in the entity's assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 18

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 20
-Subparagraph b

+ Details

Name:	us-gaap_RepaymentsOfSecuredDebt
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration