Adjusted Earnings Share Adjustment Recovery Request

No definition available.

Name:	sug_AdjustedEarningsShareAdjustmentRecoveryRequest
Namespace Prefix:	sug_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

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

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No definition available.

+ Details

Name:	sug_BaseRateIncrease
Namespace Prefix:	sug_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

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

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No definition available.

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

- Definition

Earnings Share Adjustment Recovery Amount Under Investigation

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No definition available.

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Name:	sug_EarningsShareAdjustmentRecoveryAmountUnderInvestigation
Namespace Prefix:	sug_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Recovery sought based on previous years' earnings below return on equity of 7%

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No definition available.

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Name:	sug_EarningsShareAdjustmentRecoveryRequested
Namespace Prefix:	sug_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

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

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No definition available.

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Name:	sug_PercentResidentialSmallGeneralServiceCustomers
Namespace Prefix:	sug_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

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No definition available.

+ Details

Name:	sug_PercentResidentialSmallGeneralServiceNetOperatingRevenues
Namespace Prefix:	sug_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	sug_RegulatedOperationsLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Definition

Percentage of earnings below stated return on equtiy the Company is requesting as the appropriate amount for recovery of a prior year.

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No definition available.

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Name:	sug_RemandRecoveryPercentage
Namespace Prefix:	sug_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase in revenues authorized by a regulatory authority

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No definition available.

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

Regulation and Rates Narrative (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended				3 Months Ended
	Feb. 10, 2010 Missouri Gas Energy [Member]	Apr. 02, 2009 Missouri Gas Energy [Member]	Nov. 13, 2009 New England Gas Company [Member]	Sep. 15, 2008 New England Gas Company [Member]	Mar. 31, 2012 New England Gas Company [Member]
Regulated Operations [Line Items]
Base rate increase		$ 32.4
Revenue increase authorized	16.2
Percent residential small general service customers	99.00%
Percent residential small general service net operating revenues	91.00%
Recovery amount requested based on previous years' earnings below return on equity of 7%			1.7	4.0
Recovery percentage requested of earnings below stated return on equity			50.00%	50.00%
Adjusted Earnings Share Adjustment recovery requested				4.1
Earnings Share Adjustment recovery amount under investigation			1.7
Earnings Share Adjustment (ESA) recovery approved					$ 4