SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Off System Sales (Details)	Sep. 30, 2014
Laclede Gas | First $2 million
Off System Sales [Line Items]
Customer Share	100.00%
Company Share	0.00%
Laclede Gas | Next $2 million
Off System Sales [Line Items]
Customer Share	80.00%
Company Share	20.00%
Laclede Gas | Next $2 million
Off System Sales [Line Items]
Customer Share	75.00%
Company Share	25.00%
Laclede Gas | Amounts exceeding $6 million
Off System Sales [Line Items]
Customer Share	70.00%
Company Share	30.00%
Missouri Gas Energy (MGE) | First $1.2 million
Off System Sales [Line Items]
Customer Share	85.00%
Company Share	15.00%
Missouri Gas Energy (MGE) | Next $1.2 million
Off System Sales [Line Items]
Customer Share	80.00%
Company Share	20.00%
Missouri Gas Energy (MGE) | Next $1.2 million
Off System Sales [Line Items]
Customer Share	75.00%
Company Share	25.00%
Missouri Gas Energy (MGE) | Amounts exceeding $3.6 million
Off System Sales [Line Items]
Customer Share	70.00%
Company Share	30.00%