Name:	lg_AmountRemainingOnDepositWithBrokerageFirm
Namespace Prefix:	lg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The approximate amount that the company is contractually committed to spend on a specified project.

No definition available.

Name:	lg_ApproximateContractAmountOfProject
Namespace Prefix:	lg_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
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- Details

Name:	lg_CommitmentsAbstract
Namespace Prefix:	lg_
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Period Type:	duration

- Details

Name:	lg_ContingenciesAndIndemnificationsAbstract
Namespace Prefix:	lg_
Data Type:	xbrli:stringItemType
Balance Type:	na
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The number of manufactured gas plant (MGP) sites in Missouri posing potential environmental liability at St Louis.

No definition available.

Name:	lg_NumberOfFormerManufacturedGasPlantSitesInCityOfStLouis
Namespace Prefix:	lg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of former manufactured gas plant (MGP) sites in Missouri posing potential environmental liability.

No definition available.

Name:	lg_NumberOfFormerManufacturedGasPlantSitesInMissouri
Namespace Prefix:	lg_
Data Type:	xbrli:integerItemType
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The number of manufactured gas plant (MGP) sites in Missouri posing potential environmental liability at Shrewsbury.

No definition available.

Name:	lg_NumberOfFormerManufacturedGasPlantSitesInShrewsburyMissouri
Namespace Prefix:	lg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Discloses the MoPSC Staff's proposed disallowance amount related to purchased gas costs.

No definition available.

Name:	lg_ProposedDisallowanceAmountRelatedToPurchasedGasCosts
Namespace Prefix:	lg_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

The minimum amount the entity agreed to spend under the long-term purchase commitment.

No definition available.

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The estimated maximum amount of possible loss from the contingency.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14557-108349

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 14

-Paragraph 3

-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 Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349

Name:	us-gaap_LossContingencyRangeOfPossibleLossMaximum
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Data Type:	xbrli:monetaryItemType
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The estimated minimum amount of possible loss from the contingency.

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

Cash inflow related to receipts of other deposits not otherwise defined in the taxonomy.

No definition available.