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Commitments and Contingencies - Additional Information - Contingencies (Details) | Mar. 31, 2021 site
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Spire Missouri East |
Site Contingency [Line Items] |
Number of former manufactured gas plant (MGP) sites in Missouri | 3
Number of sites enrolled in Brownfields/Voluntary clean up program | 2
Spire Missouri West | Previous Ownership |
Site Contingency [Line Items] |
Number of former manufactured gas plant (MGP) | 6
Spire Alabama |
Site Contingency [Line Items] |
Number of former manufactured gas plant (MGP) | 9
Number of former manufactured gas distribution | 5
Spire Alabama | Current Ownership |
Site Contingency [Line Items] |
Number of former manufactured gas plant (MGP) | 4
Number of former manufactured gas distribution | 1

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