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COMMITMENTS AND CONTINGENCIES - Contingencies (Details) |  | 3 Months Ended | 57 Months Ended |
--- | --- | --- | --- | ---
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 |

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