Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

Name:	invest_DerivativeNonmonetaryNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	ugu_DisclosuresAboutDerivativeInstrumentsHedgingActivitiesAdditionalTextualAbstract
Namespace Prefix:	ugu_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ugu_DisclosuresAboutDerivativeInstrumentsHedgingActivitiesTextualAbstract
Namespace Prefix:	ugu_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum length of time hedged in price risk cash flow hedges.

+ References

No definition available.

+ Details

Name:	ugu_MaximumLengthOfTimeHedgedInPriceRiskCashFlowHedges
Namespace Prefix:	ugu_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph a

-Clause 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

+ Details

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

- Definition

Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

+ Details

Name:	us-gaap_DerivativeFairValueOfDerivativeLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80748-113994

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-Subparagraph b(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

+ References

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Paragraph 80

-Subparagraph Exhibit 4-8, 3

-IssueDate 2006-05-01

-Chapter 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

+ Details

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

Disclosures About Derivative Instruments and Hedging Activities Textual (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Derivative Liabilities	$ 39,453		$ 37,782
Total Derivatives Assets	4,760		18
Disclosures About Derivative Instruments Hedging Activities (Additional Textual) [Abstract]
Amount of net losses associated with interest rate hedges to be reclassified with interest rate hedges during the next 12 months	1,043
Restricted Cash in brokerage accounts	2,106	0	3,066
Electric Utility electric transmission congestion [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Notional amount (in units)	118,200,000		130,000,000
Maximum length of time hedged in price risk cash flow hedges (in months)	5 months
Gas Utility [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Notional amount (in units)	13,000,000		9,100,000
Maximum length of time hedged in price risk cash flow hedges (in months)	9 months
Electric Utility [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Notional amount (in units)	482,300,000		816,000,000
Derivative Liabilities	8,182		13,529
Maximum length of time hedged in price risk cash flow hedges (in months)	17 months
Interest Rate Protection Agreements [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Underlying variable rate debt	173,000		173,000
Derivative financial instruments [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Interest rate contracts [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Total Derivatives Assets	4,226		0
Derivative financial instruments [Member] \| Derivatives Accounted for Under ACS 980 [Member] \| Commodity contracts [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Total Derivatives Assets	420		18
Derivative financial instruments [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Commodity contracts [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Derivative Liabilities	0		2
Total Derivatives Assets	114		0
Derivative financial instruments and other noncurrent liabilities [Member] \| Derivatives Accounted for Under ACS 980 [Member] \| Commodity contracts [Member]
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Derivative Liabilities	$ 9,041		$ 16,118