Stockholders Equity Textuals.

Name:	uns_StockholdersEquityTextualsAbstract
Namespace Prefix:	uns
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 32

+ Details

Name:	us-gaap_DividendsPayableAmountPerShare
Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow from any dividend or other distribution in cash with respect to any shares of, or other ownership interest in, an entity, except a dividend consisting of distribution of earnings or stock dividend or pro rata stock split.

+ 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 a

+ Details

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

- Definition

The cash outflow from the entity's earnings to the shareholders.

+ References

+ Details

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

- Definition

The cash inflow from parent as a source of financing that is recorded as additional paid in capital.

+ References

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

+ Details

Name:	us-gaap_ProceedsFromContributionsFromParent
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Stockholders' Equity (Details) (USD $)		1 Months Ended		6 Months Ended	1 Months Ended
Stockholders' Equity (Details) (USD $)	Jun. 30, 2011	Mar. 31, 2010 MILLENNIUM ENERGY HOLDINGS, INC. [Member]	Mar. 31, 2010 TEP [Member]	Jun. 30, 2010 TEP [Member]	Feb. 28, 2011 UNS GAS, INC. [Member]	Apr. 30, 2010 UNS GAS, INC. [Member]	Jul. 31, 2011 UES Company [Member]	Feb. 28, 2011 UES Company [Member]	Apr. 30, 2010 UES Company [Member]	Jul. 31, 2011 UNSE Company [Member]	Jul. 31, 2011 UED Company [Member]	Feb. 28, 2010 UED Company [Member]
Stockholders' Equity (Textuals) [Abstract]
Dividends declared per share	$ 0.42
Equity Investment from Parent			$ 15,000,000	$ 15,000,000			$ 20,000,000			$ 20,000,000
Return of Capital to UniSource Energy		6,000,000									25,000,000	4,000,000
Payments of dividends		$ 6,000,000			$ 10,000,000	$ 10,000,000		$ 10,000,000	$ 10,000,000		$ 36,000,000	$ 9,000,000