SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details) (USD $)
In Millions, unless otherwise specified |
Sep. 30, 2014
|
Sep. 30, 2013
|
Sep. 30, 2014
Laclede Gas
|
Sep. 30, 2013
Laclede Gas
|
Sep. 01, 2013
Laclede Gas
|
Sep. 30, 2014
Missouri Gas Energy (MGE)
|
Sep. 30, 2013
Missouri Gas Energy (MGE)
|
Sep. 01, 2013
Missouri Gas Energy (MGE)
|
Sep. 30, 2014
Missouri Gas Energy (MGE)
Laclede Gas
|
Sep. 30, 2013
Missouri Gas Energy (MGE)
Laclede Gas
|
Aug. 31, 2014
Alagasco
|
Sep. 30, 2013
Alagasco
|
Sep. 01, 2013
Alagasco
|
Sep. 30, 2014
Alagasco
Laclede Gas
|
Sep. 30, 2013
Alagasco
Laclede Gas
|
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Goodwill [Line Items] | |||||||||||||||
Goodwill | $ 937.8 | $ 247.1 | $ 210.2 | $ 247.1 | $ 210.2 | $ 210.2 | $ 247.1 | $ 210.2 | $ 210.2 | $ 247.1 | $ 727.6 | $ 0 | $ 727.6 | $ 0 | $ 0 |