CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDER'S EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common Stock Outstanding	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Laclede Gas	Laclede Gas Common Stock Outstanding	Laclede Gas Paid-in Capital	Laclede Gas Retained Earnings	Laclede Gas Accumulated Other Comprehensive Loss	Alagasco	Alagasco Common Stock Outstanding	Alagasco Paid-in Capital	Alagasco Retained Earnings
Beginning Balance at Sep. 30, 2014	$ 1,508.4	$ 43.2	$ 1,029.4	$ 437.5	$ (1.7)	$ 1,007.8	$ 0.1	$ 744.0	$ 265.6	$ (1.9)	$ 849.6	$ 0.0	$ 503.9	$ 345.7
Beginning Balance, (in shares) at Sep. 30, 2014		43,178,405					24,577					1,972,052
Stockholders' Equity Rollforward
Net income	141.5			141.5		88.9			88.9		56.9			56.9
Dividend reinvestment plan	0.9		0.9
Dividend reinvestment plan (in shares)		9,494
Stock-based compensation costs	(0.4)		(0.4)			1.7		1.7
Equity Incentive Plan	2.9	$ 0.1	2.8
Equity Incentive Plan (in shares)		125,949
Tax benefit – stock compensation	0.6		0.6			0.5		0.5
Dividends declared, common stock	(39.8)			(39.8)		(39.8)			(39.8)
Other comprehensive income, net of tax	(2.5)				(2.5)	(0.5)				(0.5)
Purchase accounting adjustments											2.4		2.4
Ending Balance at Mar. 31, 2015	1,611.6	$ 43.3	1,033.3	539.2	(4.2)	1,058.6	$ 0.1	746.2	314.7	(2.4)	908.9	$ 0.0	506.3	402.6
Ending Balance, (in shares) at Mar. 31, 2015		43,313,848					24,577					1,972,052
Beginning Balance at Sep. 30, 2015	1,573.6	$ 43.3	1,038.1	494.2	(2.0)	1,037.8	$ 0.1	748.2	291.2	(1.7)	874.6	$ 0.0	480.9	393.7
Beginning Balance, (in shares) at Sep. 30, 2015		43,335,012					24,577					1,972,052
Stockholders' Equity Rollforward
Net income	147.7			147.7		93.7			93.7		58.0
Dividend reinvestment plan	0.7		0.7
Dividend reinvestment plan (in shares)		12,704
Stock-based compensation costs	(1.5)		(1.5)			1.7		1.7
Equity Incentive Plan	3.1	$ 0.1	3.0
Equity Incentive Plan (in shares)		98,269
Return of capital to Spire											(29.0)		(29.0)
Dividends declared, common stock	(42.5)			(42.5)		(42.5)			(42.5)		(15.5)			(15.5)
Other comprehensive income, net of tax	0.3				0.3	0.2				0.2
Ending Balance at Mar. 31, 2016	$ 1,681.4	$ 43.4	$ 1,040.3	$ 599.4	$ (1.7)	$ 1,090.9	$ 0.1	$ 749.9	$ 342.4	$ (1.5)	$ 888.1	$ 0.0	$ 451.9	$ 436.2
Ending Balance, (in shares) at Mar. 31, 2016		43,445,985					24,577					1,972,052