Amount of increase over the base rate sought by a regulated company in a rate case filing

Amount of increase of the base rate authorized by a regulatory authority

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Namespace Prefix:	sug
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

Amount of recovery sought in a rate case filing for earnings share adjustment

Name:	sug_EarningsShareAdjustmentRecovery
Namespace Prefix:	sug
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

The percent of customers that are attributable to residential and small general service customers

Name:	sug_PercentResidentialSmallGeneralServiceCustomers
Namespace Prefix:	sug
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The percent of net operating revenues that are attributable to residential and small general service customers

Name:	sug_PercentResidentialSmallGeneralServiceNetOperatingRevenues
Namespace Prefix:	sug
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount the Company is requesting as the appropriate amount for recovery of a prior year.

Amount of increase in revenues authorized by a regulatory authority

Name:	sug_RevenueIncreaseAuthorized
Namespace Prefix:	sug
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

Name:	sug_SurchargeRecoveryPeriod
Namespace Prefix:	sug
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

Amount of regulatory costs not yet approved by the regulatory authority.

Name:	us-gaap_AmountOfRegulatoryCostsNotYetApproved
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	us-gaap_RegulatedOperationsAbstract
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Regulation and Rates (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended			0 Months Ended		1 Months Ended	0 Months Ended				3 Months Ended
	Dec. 13, 2010 Panhandle [Member]	Mar. 01, 2011 Panhandle [Member]	Aug. 31, 2009 Panhandle [Member]	Feb. 10, 2010 Missouri Gas Energy [Member]	Apr. 02, 2009 Missouri Gas Energy [Member]	Feb. 28, 2010 Missouri Gas Energy [Member]	Jul. 13, 2011 New England Gas Company [Member]	Sep. 16, 2010 New England Gas Company [Member]	Nov. 13, 2009 New England Gas Company [Member]	Sep. 15, 2008 New England Gas Company [Member]	Mar. 31, 2011 New England Gas Company [Member]
Regulated Operations [Abstract]
Amount Of Regulatory Costs Not Yet Approved		$ 54	$ 38
Surcharge Recovery Period	21.4
Base Rate Increase					32.4			6.2
Revenue Increase Authorized				16.2
Percent Residential Small General Service Customers						99
Percent Residential Small General Service Net Operating Revenues						91
Base Rate Increase Authorized											5.1
Earnings Share Adjustment Recovery									1.7	4.0
Remand Recovery							$ 4.1