CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares	Sep. 30, 2015	Sep. 30, 2014
Long - Term Debt - Laclede Gas:
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized (in shares)	70,000,000	70,000,000
Common stock, outstanding (in shares)	43,183,818	43,183,818
Laclede Group | 2.55% Senior Notes, due August 15, 2019
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	2.55%	2.55%
Laclede Group | 3.31% Notes Payable, due December 15, 2022
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.31%	3.31%
Laclede Group | 2.0% Series A Remarketable Subordinated Notes, due April 1, 2022
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	2.00%	2.00%
Laclede Group | 4.70% Senior Notes, due August 15, 2044
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.70%	4.70%
Laclede Gas
Long - Term Debt - Laclede Gas:
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized (in shares)	50,000,000	50,000,000
Common stock, outstanding (in shares)	24,577	24,549
Laclede Gas | 2.0% Series, due August 15, 2018
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	2.00%	2.00%
Laclede Gas | 5.5% Series, due May 1, 2019
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.50%	5.50%
Laclede Gas | 3.0% Series, due March 15, 2023
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.00%	3.00%
Laclede Gas | 3.4% Series, due August 15, 2023
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.40%	3.40%
Laclede Gas | 3.4% Series, due March 15, 2028
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.40%	3.40%
Laclede Gas | 7.0% Series, due June 1, 2029
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	7.00%	7.00%
Laclede Gas | 7.9% Series, due September 15, 2030
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	7.90%	7.90%
Laclede Gas | 6.0% Series, due May 1, 2034
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	6.00%	6.00%
Laclede Gas | 6.15% Series, due June 1, 2036
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	6.15%	6.15%
Laclede Gas | 4.625% Series, due August 15, 2043
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.625%	4.625%
Alagasco
Long - Term Debt - Laclede Gas:
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized (in shares)	3,000,000	3,000,000
Common stock, outstanding (in shares)	1,972,052	1,972,052
Alagasco | 5.368% Notes, due December 1, 2015
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.368%	5.368%
Alagasco | 5.2% Notes, due January 15, 2020
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.20%	5.20%
Alagasco | 3.86% Notes, due December 23, 2021
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.86%	3.86%
Alagasco | 3.21% Notes, due September 15, 2025
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.21%	3.21%
Alagasco | 5.7% Notes, due January 15, 2035
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.70%	5.70%
Alagasco | 5.9% Notes, due January 15, 2037
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.90%	5.90%