CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2016
Assets
Non-utility property, accumulated depreciation and amortization	$ 8.4	$ 8.1	$ 7.9
Capitalization:
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00	$ 1.00
Common stock, authorized (in shares)	70,000,000.0	70,000,000.0	70,000,000.0
Common stock, issued (in shares)	48,300,000	45,600,000	45,600,000
Common stock, outstanding (in shares)	48,300,000	45,600,000	45,600,000
Laclede Gas
Capitalization:
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00	$ 1.00
Common stock, authorized (in shares)	50,000	50,000	50,000
Common stock, issued (in shares)	24,577	24,577	24,577
Common stock, outstanding (in shares)	24,577	24,577	24,577
Alagasco
Capitalization:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, authorized (in shares)	3,000,000	3,000,000	3,000,000.0
Common stock, issued (in shares)	2,000,000	2,000,000	2,000,000
Common stock, outstanding (in shares)	2,000,000	2,000,000	2,000,000