Number Of Former Manufactured Gas Plant (MGP) Sites Enrolled In BVCP

No definition available.

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Number Of Incident Fatalities

+ References

No definition available.

+ Details

Name:	lg_NumberOfIncidentFatalities
Namespace Prefix:	lg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Site Contingency, Number of Former Manufactured Gas Distribution

+ References

No definition available.

+ Details

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

- Definition

Site Contingency, Number of Former Manufactured Gas Plant

+ References

No definition available.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of claims settled.

+ References

No definition available.

+ Details

Name:	us-gaap_LossContingencyClaimsSettledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

+ Details

Name:	us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of plaintiffs that have filed claims pertaining to a loss contingency.

+ References

No definition available.

+ Details

Name:	us-gaap_LossContingencyNumberOfPlaintiffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=lg_LacledeGasCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=lg_AlabamaGasCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=lg_MobileGasServiceCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EnvironmentalRemediationSiteAxis=lg_PreviousOwnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=lg_MissouriGasEnergyMgeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EnvironmentalRemediationSiteAxis=lg_CurrentOwnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=lg_ShrewsburyMissouriMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=lg_St.LouisMissouriMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES - Contingencies (Details)		3 Months Ended	57 Months Ended
COMMITMENTS AND CONTINGENCIES - Contingencies (Details)	Dec. 17, 2013 fatality	Dec. 31, 2016 lawsuit site plaintiff	Dec. 31, 2016 lawsuit site	Sep. 30, 2014 site
Laclede Gas
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP) sites in Missouri		4	4
Number of former manufactured gas plant (MGP) sites enrolled in BVCP		2	2
Alagasco
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP)		9	9
Number of former manufactured gas distribution		5	5
Number of incident fatalities \| fatality	1
Mobile Gas Service Corporation [Member]
Loss Contingencies [Line Items]
Number of lawsuits filed \| lawsuit			14
Number of lawsuits settled \| lawsuit			11
Number of lawsuits pending \| lawsuit		3	3
Previous Ownership \| Laclede Gas
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP)				19
Previous Ownership \| Missouri Gas Energy (MGE)
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP)		7	7
Previous Ownership \| Mobile Gas Service Corporation [Member]
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP)		1	1
Current Ownership \| Alagasco
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP)		4	4
Number of former manufactured gas distribution		1	1
Pending Litigation [Member] \| Mobile Gas Service Corporation [Member]
Loss Contingencies [Line Items]
Number of plaintiffs \| plaintiff		270
Shrewsbury, Missouri \| Laclede Gas
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP) sites in Missouri		1	1
St. Louis, Missouri \| Laclede Gas
Loss Contingencies [Line Items]
Number of former manufactured gas plant (MGP) sites in Missouri		3	3