Spire Missouri 10-K15 Nov 172017 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Sep. 30, 2017	Nov. 10, 2017	Mar. 31, 2017
Entity Information [Line Items]
Entity Registrant Name	SPIRE INC
Entity Central Index Key	1,126,956
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,989,327,838
Entity Common Stock, Shares Outstanding		48,266,858
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Spire Missouri
Entity Information [Line Items]
Entity Registrant Name	SPIRE MISSOURI INC
Entity Central Index Key	57,183
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			0
Entity Common Stock, Shares Outstanding		24,577
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Spire Alabama
Entity Information [Line Items]
Entity Registrant Name	SPIRE ALABAMA INC
Entity Central Index Key	3,146
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 0
Entity Common Stock, Shares Outstanding		1,972,052
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Operating Revenues:
Gas Utility	$ 1,660	$ 1,457.2	$ 1,891.8
Gas Marketing and other	80.7	80.1	84.6
Total Operating Revenues	1,740.7	1,537.3	1,976.4
Gas Utility
Natural and propane gas	570.5	492.2	882.4
Other operation and maintenance expenses	405	377.5	390.6
Depreciation and amortization	153.5	136.9	129.9
Taxes, other than income taxes	137.8	125.2	142.1
Total Gas Utility Operating Expenses	1,266.8	1,131.8	1,545
Gas Marketing and other	152.2	123.2	158.9
Total Operating Expenses	1,419	1,255	1,703.9
Operating Income	321.7	282.3	272.5
Other Income – Net	6.6	8.6	1.2
Interest Charges:
Interest on long-term debt	76.8	67.6	66.6
Other interest charges	12.3	9.6	8
Total Interest Charges	89.1	77.2	74.6
Income Before Income Taxes	239.2	213.7	199.1
Income Tax Expense	77.6	69.5	62.2
Net Income	$ 161.6	$ 144.2	$ 136.9
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	46.9	44.1	43.2
Diluted (in shares)	47	44.3	43.3
Basic Earnings Per Share of Common Stock (in dollars per share)	$ 3.44	$ 3.26	$ 3.16
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ 3.43	$ 3.24	$ 3.16
Spire Missouri
Operating Revenues:
Gas Utility	$ 1,171.9	$ 1,087.5	$ 1,416.6
Total Operating Revenues	1,171.9	1,087.5	1,416.6
Gas Utility
Natural and propane gas	538.3	471.3	786.1
Other operation and maintenance expenses	243.8	244.4	253.6
Depreciation and amortization	93.1	88.6	82.6
Taxes, other than income taxes	99.8	96.3	108.9
Total Operating Expenses	975	900.6	1,231.2
Operating Income	196.9	186.9	185.4
Other Income – Net	2.7	1.8	(0.5)
Interest Charges:
Interest on long-term debt	32.9	32.9	33.1
Other interest charges	6.2	4.5	3.3
Total Interest Charges	39.1	37.4	36.4
Income Before Income Taxes	160.5	151.3	148.5
Income Tax Expense	47.5	45.4	43.2
Net Income	113	105.9	105.3
Spire Alabama
Operating Revenues:
Gas Utility	400.5	368.5	479.2
Total Operating Revenues	400.5	368.5	479.2
Gas Utility
Natural and propane gas	84.5	67.3	171.5
Other operation and maintenance expenses	130.4	133.5	138
Depreciation and amortization	49.9	47.8	47.3
Taxes, other than income taxes	29.9	28.4	33.2
Total Operating Expenses	294.7	277	390
Operating Income	105.8	91.5	89.2
Other Income – Net	2.5	7.9	2
Interest Charges:
Interest on long-term debt	11.2	11.4	11.6
Other interest charges	3.2	2.4	2.3
Total Interest Charges	14.4	13.8	13.9
Income Before Income Taxes	93.9	85.6	77.3
Income Tax Expense	35.8	32.4	29.3
Net Income	$ 58.1	$ 53.2	$ 48

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Net income	$ 161.6	$ 144.2	$ 136.9
Cash flow hedging derivative instruments:
Net hedging gain (loss) arising during the period	11.5	(4)	(5.5)
Reclassification adjustment for loss included in net income	0	1.1	4.4
Net unrealized gain (loss) on cash flow hedging derivative instruments	11.5	(2.9)	(1.1)
Defined benefit pension and other postretirement benefit plans:
Net actuarial gain arising during the period	0	0	0.1
Amortization of actuarial loss (gain) included in net periodic pension and postretirement benefit cost	0.4	(0.3)	0.4
Net defined benefit pension and other postretirement benefit plans	0.4	(0.3)	0.5
Loss on available for sale securities	(0.1)	0	0
Other Comprehensive Income (Loss), Before Tax	11.8	(3.2)	(0.6)
Income Tax Expense (Benefit) Related to Items of Other Comprehensive Income (Loss)	4.4	(1)	(0.3)
Other Comprehensive Income (Loss), Net of Tax	7.4	(2.2)	(0.3)
Comprehensive Income	169	142	136.6
Spire Missouri
Net income	113	105.9	105.3
Cash flow hedging derivative instruments:
Net hedging gain (loss) arising during the period	0.1	0	(1.2)
Reclassification adjustment for loss included in net income	(0.2)	0.5	0.9
Net unrealized gain (loss) on cash flow hedging derivative instruments	(0.1)	0.5	(0.3)
Defined benefit pension and other postretirement benefit plans:
Net actuarial gain arising during the period	0	0	0.1
Amortization of actuarial loss (gain) included in net periodic pension and postretirement benefit cost	0.3	(0.3)	0.4
Net defined benefit pension and other postretirement benefit plans	0.3	(0.3)	0.5
Loss on available for sale securities	(0.1)	(0.1)	0
Other Comprehensive Income (Loss), Before Tax	0.1	0.1	0.2
Income Tax Expense (Benefit) Related to Items of Other Comprehensive Income (Loss)	0	0.2	0
Other Comprehensive Income (Loss), Net of Tax	0.1	(0.1)	0.2
Comprehensive Income	$ 113.1	$ 105.8	$ 105.5

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
ASSETS
Utility Plant	$ 5,278.4	$ 4,793.6
Less: Accumulated depreciation and amortization	1,613.2	1,506.4
Net Utility Plant	3,665.2	3,287.2
Non-utility property (net of accumulated depreciation and amortization, $8.6 and $8.1 at September 30, 2017 and 2016, respectively)	52	13.7
Goodwill	1,171.6	1,164.9
Other investments	64.2	62.1
Other Property and Investments	1,287.8	1,240.7
Current Assets:
Cash and cash equivalents	7.4	5.2
Accounts receivable:
Utility	140.5	127.8
Other	149.2	113.4
Allowance for doubtful accounts	(18.3)	(20.5)
Delayed customer billings	3.4	1.6
Inventories:
Natural gas	194.9	174
Propane gas	12	12
Materials and supplies	18.9	16.3
Natural gas receivable	1.9	9.7
Derivative instrument assets	5.9	11.4
Unamortized purchased gas adjustments	102.6	49.7
Other regulatory assets	72.9	44.2
Prepayments and other	34.2	24.8
Total Current Assets	725.5	569.6
Deferred Charges:
Regulatory assets	791.1	838
Other	77.1	128.9
Total Deferred Charges	868.2	966.9
Total Assets	6,546.7	6,064.4
Capitalization:
Common stock equity	1,991.3	1,768.2
Long-term debt	1,995	1,820.7
Total Capitalization	3,986.3	3,588.9
Current Liabilities:
Current portion of long-term debt	100	250
Notes payable	477.3	398.7
Accounts payable	257.1	210.9
Advance customer billings	32	70.2
Wages and compensation accrued	38.7	39.8
Dividends payable	26.6	23.5
Customer deposits	34.9	34.9
Interest accrued	14.6	14.8
Unamortized purchased gas adjustments	1	1.7
Taxes accrued	61	55.2
Other regulatory liabilities	21.6	28.9
Other	33.1	32.7
Total Current Liabilities	1,097.9	1,161.3
Deferred Credits and Other Liabilities:
Deferred income taxes	707.5
Deferred income taxes		607.3
Pension and postretirement benefit costs	237.4	303.7
Asset retirement obligations	296.6	206.4
Regulatory liabilities	157.2	130.7
Other	63.8	66.1
Total Deferred Credits and Other Liabilities	1,462.5	1,314.2
Commitments and Contingencies
Total Capitalization and Liabilities	6,546.7	6,064.4
Spire Missouri
ASSETS
Utility Plant	3,091.8	2,718.5
Less: Accumulated depreciation and amortization	681.6	604.5
Net Utility Plant	2,410.2	2,114
Goodwill	210.2	210.2
Other investments	59.4	57.3
Other Property and Investments	269.6	267.5
Current Assets:
Cash and cash equivalents	2.5	2.1
Accounts receivable:
Utility	101.7	87.9
Other	15	11.4
Allowance for doubtful accounts	(14.1)	(16.1)
Delayed customer billings	3.4	1.6
Receivables from associated companies	3.3	2.2
Inventories:
Natural gas	138.2	127.3
Propane gas	12	12
Materials and supplies	11.3	9.2
Derivative instrument assets	0.1	4.9
Unamortized purchased gas adjustments	57.4	43.1
Other regulatory assets	38.2	23.9
Prepayments and other	19.6	14.5
Total Current Assets	388.6	324
Deferred Charges:
Regulatory assets	557.8	589.8
Other	5.3	1.1
Total Deferred Charges	563.1	590.9
Total Assets	3,631.5	3,296.4
Capitalization:
Common stock equity	1,171	1,068.5
Long-term debt	873.9	804.1
Total Capitalization	2,044.9	1,872.6
Current Liabilities:
Current portion of long-term debt	100	0
Notes payable	0	243.7
Notes payable – associated companies	203	0
Accounts payable	89.9	67.6
Accounts payable to associated companies	5.4	5.4
Advance customer billings	13.3	49.1
Wages and compensation accrued	29.6	29.9
Dividends payable	0	14
Customer deposits	13.3	13.5
Interest accrued	8	7.7
Taxes accrued	34.1	29.1
Other regulatory liabilities	2.7	1.3
Other	8.5	9.9
Total Current Liabilities	507.8	471.2
Deferred Credits and Other Liabilities:
Deferred income taxes	623.8
Deferred income taxes		556.9
Pension and postretirement benefit costs	173	211.8
Asset retirement obligations	158.6	75.2
Regulatory liabilities	81.2	67.3
Other	42.2	41.4
Total Deferred Credits and Other Liabilities	1,078.8	952.6
Commitments and Contingencies
Total Capitalization and Liabilities	3,631.5	3,296.4
Spire Alabama
ASSETS
Utility Plant	1,838	1,729.6
Less: Accumulated depreciation and amortization	782	756.6
Net Utility Plant	1,056	973
Current Assets:
Cash and cash equivalents	0.1	0
Accounts receivable:
Utility	32	34
Other	6.2	7.2
Allowance for doubtful accounts	(2.6)	(3.3)
Inventories:
Natural gas	33.9	34.6
Materials and supplies	6.5	5.9
Unamortized purchased gas adjustments	45.2	5.6
Other regulatory assets	19.4	14.9
Prepayments and other	6.7	5.1
Total Current Assets	147.4	104
Deferred Charges:
Regulatory assets	197	230.7
Deferred income tax	185.6
Deferred income tax		221.4
Other	57	60.8
Total Deferred Charges	439.6	512.9
Total Assets	1,643	1,589.9
Capitalization:
Common stock equity	867.4	867.3
Long-term debt	247.8	247.6
Total Capitalization	1,115.2	1,114.9
Current Liabilities:
Notes payable	0	82
Accounts payable	44.4	34.3
Accounts payable to associated companies	1.6	0.4
Advance customer billings	18.6	21.1
Wages and compensation accrued	7.4	7.8
Customer deposits	17.9	18.2
Interest accrued	3.3	3.3
Taxes accrued	23.4	21.6
Other regulatory liabilities	12	22.7
Other	2.9	6.3
Total Current Liabilities	301.4	217.7
Deferred Credits and Other Liabilities:
Pension and postretirement benefit costs	50.2	74.3
Asset retirement obligations	128.4	120.1
Regulatory liabilities	39.6	41.7
Other	8.2	21.2
Total Deferred Credits and Other Liabilities	226.4	257.3
Total Capitalization and Liabilities	$ 1,643	$ 1,589.9

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Assets
Non-utility property, accumulated depreciation and amortization	$ 8.6	$ 8.1

CONSOLIDATED STATEMENTS OF CAPI

CONSOLIDATED STATEMENTS OF CAPITALIZATION - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Common Stock Equity:
Common stock, par value $1 per share	$ 48.3	$ 45.6
Paid-in capital	1,325.6	1,175.9
Retained earnings	614.2	550.9
Accumulated other comprehensive income (loss)	3.2	(4.2)
Total Common Stock Equity	1,991.3	1,768.2
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	2,012	1,835.8
Unamortized debt issuance costs	(15.2)	(13)
Unamortized discounts on long-term debt	(1.8)	(2.1)
Total Long-Term Debt	1,995	1,820.7
Total Capitalization	3,986.3	3,588.9
Spire \| 2.55% Senior Notes, due August 15, 2019
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	125	125
Spire \| 2.52% Senior Notes, due September 1, 2021
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	35	35
Spire \| 2.0% Series A Remarketable Subordinated Notes, due April 1, 2022
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	0	143.8
Spire \| 3.31% Notes Payable, due December 15, 2022
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	25	25
Spire \| 3.54% Senior Notes, due February 27, 2024
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	150	0
Spire \| 3.13% Senior Notes, due September 1, 2026
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	130	130
Spire \| 3.93% Senior Notes, due March 15, 2027
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	100	0
Spire \| 4.70% Senior Notes, due August 15, 2044
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	250	250
Spire Missouri
Common Stock Equity:
Common stock, par value $1 per share	0.1	0.1
Paid-in capital	756.1	751.9
Retained earnings	416.5	318.3
Accumulated other comprehensive income (loss)	(1.7)	(1.8)
Total Common Stock Equity	1,171	1,068.5
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	880	810
Unamortized debt issuance costs	(4.6)	(4.2)
Unamortized discounts on long-term debt	(1.5)	(1.7)
Total Long-Term Debt	873.9	804.1
Total Capitalization	2,044.9	1,872.6
Spire Missouri \| 2.0% Series, due August 15, 2018
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	0	100
Spire Missouri \| 5.5% Series, due May 1, 2019
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	50	50
Spire Missouri \| 3.0% Series, due March 15, 2023
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	55	55
Spire Missouri \| 3.4% Series, due August 15, 2023
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	250	250
Spire Missouri \| 3.4% Series, due March 15, 2028
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	45	45
Spire Missouri \| 7.0% Series, due June 1, 2029
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	25	25
Spire Missouri \| 7.9% Series, due September 15, 2030
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	30	30
Spire Missouri \| 3.68% Series, due September 15, 2032
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	50	0
Spire Missouri \| 6.0% Series, due May 1, 2034
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	100	100
Spire Missouri \| 6.15% Series, due June 1, 2036
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	55	55
Spire Missouri \| 4.625% Series, due August 15, 2043
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	100	100
Spire Missouri \| 4.38% Series, due September 15, 2057
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	70	0
Spire Missouri \| 4.38% Series, due September 15, 2057
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	50	0
Spire Alabama
Common Stock Equity:
Common stock, par value $1 per share, and paid-in capital	420.9	451.9
Retained earnings	446.5	415.4
Total Common Stock Equity	867.4	867.3
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	250	250
Unamortized debt issuance costs	(2.2)	(2.4)
Total Long-Term Debt	247.8	247.6
Total Capitalization	1,115.2	1,114.9
Spire Alabama \| 5.2% Notes, due January 15, 2020
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	40	40
Spire Alabama \| 3.86% Notes, due December 23, 2021
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	50	50
Spire Alabama \| 3.21% Notes, due September 15, 2025
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	35	35
Spire Alabama \| 5.9% Notes, due January 15, 2037
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	45	45
Spire Alabama \| 4.31% Notes, due December 1, 2045
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	80	80
Other \| 3.10% Note, due December 30, 2018
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	5	5
Other \| 4.14% First Mortgage Bonds, due September 30, 2021
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	20	20
Other \| 5.00% First Mortgage Bonds, due September 30, 2031
Long-Term Debt - Laclede Gas:
Debt instrument, principal outstanding	$ 42	$ 42

CONSOLIDATED STATEMENTS OF CAP7

CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares	Sep. 30, 2017	Sep. 30, 2016
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)	48,263,243	45,650,642
Spire Missouri
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	24,577
Spire Missouri \| 2.0% Series, due August 15, 2018
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	2.00%	2.00%
Spire Missouri \| 5.5% Series, due May 1, 2019
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.50%	5.50%
Spire Missouri \| 3.0% Series, due March 15, 2023
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.00%	3.00%
Spire Missouri \| 3.4% Series, due August 15, 2023
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.40%	3.40%
Spire Missouri \| 3.4% Series, due March 15, 2028
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.40%	3.40%
Spire Missouri \| 7.0% Series, due June 1, 2029
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	7.00%	7.00%
Spire Missouri \| 7.9% Series, due September 15, 2030
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	7.90%	7.90%
Spire Missouri \| 6.0% Series, due May 1, 2034
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	6.00%	6.00%
Spire Missouri \| 6.15% Series, due June 1, 2036
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	6.15%	6.15%
Spire Missouri \| 4.625% Series, due August 15, 2043
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.625%	4.625%
Spire Missouri \| 4.38% Series, due September 15, 2057
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.38%	4.38%
Spire Missouri \| 4.38% Series, due September 15, 2057
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.23%	4.23%
Spire Missouri \| 3.68% Series, due September 15, 2032
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.68%	3.68%
Spire Alabama
Long - Term Debt - Laclede Gas:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	3,000,000	3,000,000
Common stock, outstanding (in shares)	1,972,052	1,972,052
Spire Alabama \| 5.2% Notes, due January 15, 2020
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.20%	5.20%
Spire Alabama \| 3.86% Notes, due December 23, 2021
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.86%	3.86%
Spire Alabama \| 3.21% Notes, due September 15, 2025
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.21%	3.21%
Spire Alabama \| 5.9% Notes, due January 15, 2037
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.90%	5.90%
Spire Alabama \| 4.31% Notes, due December 1, 2045
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.31%	4.31%
Other \| 3.10% Note, due December 30, 2018
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.10%	3.10%
Other \| 4.14% First Mortgage Bonds, due September 30, 2021
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.14%	4.14%
Other \| 5.00% First Mortgage Bonds, due September 30, 2031
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	5.00%	5.00%
Spire \| 2.52% Senior Notes, due September 1, 2021
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	2.55%	2.55%
Spire \| 2.0% Series A Remarketable Subordinated Notes, due April 1, 2022
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	2.52%	2.52%
Spire \| 3.31% Notes Payable, due December 15, 2022
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.31%	3.31%
Spire \| 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%
Spire \| 3.13% Senior Notes, due September 1, 2026
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.13%	3.13%
Spire \| 3.93% Senior Notes, due March 15, 2027
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.93%	3.93%
Spire \| 4.70% Senior Notes, due August 15, 2044
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	4.70%	4.70%
Spire \| 3.54% Senior Notes, due February 27, 2024
Long - Term Debt - Laclede Gas:
Debt instrument, interest rate, stated percentage	3.54%	3.54%

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock Outstanding	Paid-in Capital	Retained Earnings	AOCI	Spire Missouri	Spire MissouriCommon Stock Outstanding	Spire MissouriPaid-in Capital	Spire MissouriRetained Earnings	Spire MissouriAOCI	Spire Alabama	Spire AlabamaCommon Stock Outstanding	Spire AlabamaPaid-in Capital	Spire AlabamaRetained Earnings
BALANCE (in shares) at Sep. 30, 2014		43,178,405					24,577					1,972,052
BALANCE at Sep. 30, 2014	$ 1,508.4	$ 43.2	$ 1,029.4	$ 437.5	$ (1.7)	$ 1,007.8	$ 0.1	$ 744	$ 265.6	$ (1.9)	$ 849.6	$ 0	$ 503.9	$ 345.7
Stockholders' Equity Rollforward
Net income	136.9			136.9		105.3			105.3		48			48
Purchase accounting adjustments											4		4
Common stock offering (in shares)												0
Common stock offering											(27)		(27)
Dividend reinvestment plan (in shares)		31,166
Dividend reinvestment plan	1.6	$ 0	1.6
Stock-based compensation costs	6.7		6.7			3.7		3.7
Stock issued under stock-based compensation plans (in shares)		156,925
Stock issued under stock-based compensation plans	1.4	$ 0.1	1.3
Employees’ tax withholding for stock-based compensation (in shares)		(31,484)
Employees’ tax withholding for stock-based compensation	(1.6)		(1.6)
Tax benefit - stock compensation	0.7		0.7			0.5		0.5
Dividends declared	(80.2)			(80.2)		(79.7)			(79.7)
Other comprehensive loss, net of tax	(0.3)				(0.3)	0.2				0.2
BALANCE (in shares) at Sep. 30, 2015		43,335,012					24,577					1,972,052
BALANCE at Sep. 30, 2015	1,573.6	$ 43.3	1,038.1	494.2	(2)	1,037.8	$ 0.1	748.2	291.2	(1.7)	874.6	$ 0	480.9	393.7
Stockholders' Equity Rollforward
Net income	144.2			144.2		105.9			105.9		53.2			53.2
Common stock offering (in shares)		2,185,000
Common stock offering	133.2	$ 2.2	131
Dividend reinvestment plan (in shares)		22,878
Dividend reinvestment plan	1.4		1.4
Stock-based compensation costs	6.7		6.7			3.7		3.7
Stock issued under stock-based compensation plans (in shares)		136,979
Stock issued under stock-based compensation plans	0.5	$ 0.1	0.4
Employees’ tax withholding for stock-based compensation (in shares)		(29,227)
Employees’ tax withholding for stock-based compensation	(1.7)		(1.7)
Dividends declared	(87.5)			(87.5)		(78.8)			(78.8)
Return of capital to Spire											(29)		(29)
Other comprehensive loss, net of tax	(2.2)				(2.2)	(0.1)				(0.1)
BALANCE (in shares) at Sep. 30, 2016		45,650,642					24,577					1,972,052
BALANCE at Sep. 30, 2016	1,768.2	$ 45.6	1,175.9	550.9	(4.2)	1,068.5	$ 0.1	751.9	318.3	(1.8)	867.3	$ 0	451.9	415.4
Stockholders' Equity Rollforward
Net income	161.6			161.6		113			113		58.1			58.1
Common stock offering (in shares)		2,504,684
Common stock offering	145.5	$ 2.5	143
Dividend reinvestment plan (in shares)		23,731
Dividend reinvestment plan	1.6		1.6
Stock-based compensation costs						4.2		4.2
Stock issued under stock-based compensation plans (in shares)		119,700
Stock issued under stock-based compensation plans	0.1	$ 0.2	(0.1)
Employees’ tax withholding for stock-based compensation (in shares)		(35,514)
Employees’ tax withholding for stock-based compensation	(2.2)		(2.2)
Dividends declared	(99.2)			(99.2)		(14.8)			(14.8)		(27)			(27)
Return of capital to Spire											(31)		(31)
Other comprehensive loss, net of tax	7.4				7.4	0.1				0.1
BALANCE (in shares) at Sep. 30, 2017		48,263,243					24,577					1,972,052
BALANCE at Sep. 30, 2017	1,991.3	$ 48.3	1,325.6	614.2	$ 3.2	$ 1,171	$ 0.1	$ 756.1	$ 416.5	$ (1.7)	$ 867.4	$ 0	$ 420.9	$ 446.5
Stockholders' Equity Rollforward
Stock-based compensation costs (After Adoption)	$ 8.3		$ 7.4	$ 0.9

CONSOLIDATED STATEMENTS OF COM9

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement of Stockholders' Equity [Abstract]
Dividends declared, common stock (in dollars per share)	$ 2.10	$ 1.96	$ 1.84

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Operating Activities:
Net income	$ 161.6	$ 144.2	$ 136.9
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	154.1	137.5	130.8
Deferred income taxes and investment tax credits	77	68.8	65.5
Changes in assets and liabilities:
Accounts receivable – net	(63)	(12.3)	(4.8)
Unamortized purchased gas adjustments	(50.9)	(52.8)	27.1
Accounts payable	51.1	30	(30)
Delayed/advance customer billings – net	(40)	26.9	20.3
Taxes accrued	5.8	(0.4)	(17)
Inventories	(23.5)	16.5	54.8
Other assets and liabilities	11.9	(35)	(67.6)
Other	4.2	4.9	6.4
Net cash provided by operating activities	288.3	328.3	322.4
Investing Activities:
Capital expenditures	(438.1)	(293.3)	(289.8)
Acquisition of Spire EnergySouth (net of $2.0 cash acquired) and final settlement	3.8	(317.7)	0
Final settlement related to acquisition of Spire Alabama	0	0	(8.2)
Other	0.8	(1.7)	(0.7)
Net cash used in investing activities	(433.5)	(612.7)	(298.7)
Financing Activities:
Issuance of long-term debt	420	245	35
Repayment of long-term debt	(393.8)	(80)	(34.8)
Issuance of short-term debt - net	78.6	60.7	50.8
Issuance of common stock	146.9	137.1	3.1
Dividends paid	(96.2)	(85.2)	(79)
Other	(8.1)	(1.8)	(1.1)
Net cash provided by (used in) financing activities	147.4	275.8	(26)
Net Increase (Decrease) in Cash and Cash Equivalents	2.2	(8.6)	(2.3)
Cash and Cash Equivalents at Beginning of Year	5.2	13.8	16.1
Cash and Cash Equivalents at End of Year	7.4	5.2	13.8
Supplemental disclosure of cash (paid) refunded for:
Interest	(85.5)	(72.5)	(65.3)
Income taxes	(1.3)	2.9	1.3
Spire Missouri
Operating Activities:
Net income	113	105.9	105.3
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	93.1	88.6	82.6
Deferred income taxes and investment tax credits	47.5	45.3	45.4
Changes in assets and liabilities:
Accounts receivable – net	(20.5)	35.7	9.9
Unamortized purchased gas adjustments	(11.6)	(18.7)	21.3
Accounts payable	16.8	0.9	(11.4)
Delayed/advance customer billings – net	(37.6)	24.9	17.9
Taxes accrued	5	4.9	(14.6)
Inventories	(13)	11	51.2
Other assets and liabilities	(11.6)	(29.6)	(32.8)
Other	1.6	2.3	2.8
Net cash provided by operating activities	182.7	271.2	277.6
Investing Activities:
Capital expenditures	(282.2)	(197.8)	(198.6)
Other	1.1	1.1	2.9
Net cash used in investing activities	(281.1)	(196.7)	(195.7)
Financing Activities:
Issuance of first mortgage bonds	170	0	0
Issuance of short-term debt - net	(243.7)	10.7	(5.7)
Borrowings from Spire	203	0	18.4
Repayment of borrowings from Spire	0	0	(18.4)
Dividends paid	(28.7)	(84.8)	(78.7)
Other	(1.8)	0	0.5
Net cash provided by (used in) financing activities	98.8	(74.1)	(83.9)
Net Increase (Decrease) in Cash and Cash Equivalents	0.4	0.4	(2)
Cash and Cash Equivalents at Beginning of Year	2.1	1.7	3.7
Cash and Cash Equivalents at End of Year	2.5	2.1	1.7
Supplemental disclosure of cash (paid) refunded for:
Interest	(38.6)	(35.7)	(31)
Income taxes	0	2.1	0.7
Spire Alabama
Operating Activities:
Net income	58.1	53.2	48
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	49.9	47.8	47.3
Deferred income taxes and investment tax credits	35.8	33.2	29.2
Changes in assets and liabilities:
Accounts receivable – net	(10)	(11.1)	(9.1)
Unamortized purchased gas adjustments	(39.6)	(33.8)	5.8
Accounts payable	8.8	9.1	(10.4)
Delayed/advance customer billings – net	(2.5)	2	2.4
Taxes accrued	1.8	(5.2)	(4)
Inventories	0.1	5.3	7.2
Other assets and liabilities	(16.6)	(3.2)	(18)
Other	(1.3)	0.9	2
Net cash provided by operating activities	84.5	98.2	100.4
Investing Activities:
Capital expenditures	(113.9)	(93.4)	(85.8)
Other	(0.4)	(2.5)	(1)
Net cash used in investing activities	(114.3)	(95.9)	(86.8)
Financing Activities:
Issuance of long-term debt	0	80	35
Repayment of long-term debt	0	(80)	(34.8)
Issuance of short-term debt - net	(82)	51	15
Borrowings from Spire	169.9	0	0
Return of capital to Spire	(31)	(29)	(27)
Dividends paid	(27)	(31.5)	0
Other	0	0	(0.2)
Net cash provided by (used in) financing activities	29.9	(9.5)	(12)
Net Increase (Decrease) in Cash and Cash Equivalents	0.1	(7.2)	1.6
Cash and Cash Equivalents at Beginning of Year	0	7.2	5.6
Cash and Cash Equivalents at End of Year	0.1	0	7.2
Supplemental disclosure of cash (paid) refunded for:
Interest	(12.8)	(12.4)	(12.3)
Income taxes	$ 0	$ 0.8	$ 0

CONSOLIDATED STATEMENTS OF CA11

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2015
Statement of Cash Flows [Abstract]
Cash acquired from acquisition	$ 2	$ 12.1

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Sep. 30, 2017
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION – These notes are an integral part of the accompanying audited financial statements of Spire Inc. presented on a consolidated basis (Spire or the Company), Spire Missouri Inc. (Spire Missouri or the Missouri Utilities) and Spire Alabama Inc. (Spire Alabama). Spire Missouri and Spire Alabama are wholly owned subsidiaries of the Company. Spire Missouri changed its name from Laclede Gas Company on August 30, 2017, and Spire Alabama changed its name from Alabama Gas Corporation on September 1, 2017. Spire Missouri, Spire Alabama and the subsidiaries of Spire EnergySouth Inc. (formerly known as EnergySouth, Inc.) are collectively referred to as the Utilities. The subsidiaries of Spire EnergySouth Inc. (Spire EnergySouth) are Spire Gulf Inc. (Spire Gulf, formerly known as Mobile Gas Service Corporation) and Spire Mississippi Inc. (Spire Mississippi, formerly known as Willmut Gas & Oil Company). The accompanying audited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). Unless otherwise indicated, references to years herein are references to the fiscal years ending September 30 for the Company and its subsidiaries. The consolidated financial position, results of operations, and cash flows of Spire are primarily derived from the financial position, results of operations, and cash flows of the Utilities. In compliance with GAAP, transactions between Spire Missouri and Spire Alabama and their affiliates, as well as intercompany balances on their balance sheets, have not been eliminated from their separate financial statements. The Company’s September 12, 2016 acquisition of Spire EnergySouth is included in the results of operations since the acquisition date and impacts the comparability of the financial statement periods presented for the Company. For a further discussion of the acquisition, see Note 2 , Acquisitions. The Utilities are regulated natural gas distribution utilities. Due to the seasonal nature of the Utilities, the earnings of Spire, Spire Missouri and Spire Alabama are typically concentrated during the heating season of November through April each fiscal year. NATURE OF OPERATIONS – Spire Inc. (NYSE: SR) is a public utility holding company with principal offices in St. Louis, Missouri. The Company has two reportable segments: Gas Utility and Gas Marketing. The Gas Utility segment consists of the regulated natural gas distribution operations of the Company and is the core business segment of Spire in terms of revenue and earnings generation. The Gas Utility segment is comprised of the operations of: the Missouri Utilities, serving St. Louis and eastern Missouri (Spire Missouri East) and Kansas City and western Missouri (Spire Missouri West, formerly Missouri Gas Energy, or MGE); Spire Alabama, serving central and northern Alabama; and the subsidiaries of Spire EnergySouth, serving southern Alabama and south-central Mississippi. Spire’s primary non-utility business, Spire Marketing Inc. (Spire Marketing), included in the Gas Marketing segment, provides non-regulated natural gas services. The activities of other subsidiaries are described in Note 14 , Information by Operating Segment, and are reported as Other. Spire Missouri and Spire Alabama each have a single reportable segment. USE OF ESTIMATES – The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. SYSTEM OF ACCOUNTS – The accounts of the Utilities are maintained in accordance with the Uniform System of Accounts prescribed by the applicable state public service commissions, which systems substantially conform to that prescribed by the Federal Energy Regulatory Commission (FERC). PROPERTY, PLANT, AND EQUIPMENT – Utility Plant – Utility plant is stated at original cost. The cost of additions to utility plant includes contracted work, direct labor and materials, allocable overheads, and an allowance for funds used during construction. The costs of units of property retired, replaced, or renewed are removed from utility plant and are charged to accumulated depreciation. Maintenance and repairs of property and replacement and renewal of items determined to be less than units of property are charged to maintenance expenses. For Spire Missouri, utility plant is depreciated on a straight-line basis at rates based on estimated service lives of the various classes of property. In fiscal years 2017 , 2016 and 2015 , annual depreciation and amortization expense averaged 3.0% of the original cost of depreciable and amortizable property. For Spire Alabama, depreciation is provided using the composite method of depreciation on a straight-line basis over the estimated useful lives of utility property at rates approved by the Alabama Public Service Commission (APSC). The composite depreciation rate is approximately 3.1% . Non-utility Property – Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services and, for FERC-regulated projects, an allowance for funds used during construction. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the difference is recorded as a loss in the income statements. Accrued Capital Expenditures – Accrued capital expenditures, shown in the following table, are excluded from capital expenditures in the statements of cash flows. September 30 2017 2016 2015 Spire $ 41.0 $ 30.4 $ 13.4 Spire Missouri 28.9 14.8 9.6 Spire Alabama 9.4 6.8 3.1 ASSET RETIREMENT OBLIGATIONS – Spire, Spire Missouri, and Spire Alabama record legal obligations associated with the retirement of long-lived assets in the period in which the obligations are incurred, if sufficient information exists to reasonably estimate the fair value of the obligations. Obligations are recorded as both a cost of the related long-lived asset and as a corresponding liability. Subsequently, the asset retirement costs are depreciated over the life of the asset and the asset retirement obligations are accreted to the expected settlement amounts. The Company, Spire Missouri and Spire Alabama record asset retirement obligations associated with certain safety requirements to purge and seal gas distribution mains upon retirement, the plugging and abandonment of storage wells and other storage facilities, specific service line obligations, and certain removal and disposal obligations related to components of Spire Missouri’s, Spire Alabama’s and Spire Gulf’s distribution systems and general plant. Asset retirement obligations recorded by Spire’s other subsidiaries are not material. As authorized by the Missouri Public Service Commission (MoPSC) and APSC, Spire Missouri, Spire Alabama and Spire Gulf accrue future asset removal costs associated with their property, plant and equipment even if a legal obligation does not exist. Such accruals are provided for through depreciation expense and are recorded with corresponding credits to regulatory liabilities or regulatory assets. When those utilities retire depreciable utility plant and equipment, they charge the associated original costs to accumulated depreciation and amortization, and any related removal costs incurred are charged to regulatory liabilities or regulatory assets. The difference between removal costs recognized in depreciation rates and the accretion expense and depreciation expense recognized for financial reporting purposes is a timing difference between recovery of these costs in rates and their recognition for financial reporting purposes. Accordingly, these differences are deferred as regulatory liabilities or regulatory assets. In the rate setting process, the regulatory liabilities or regulatory assets are excluded from the rate base upon which those utilities have the opportunity to earn their allowed rates of return. The costs associated with asset retirement obligations of Spire Missouri, Spire Alabama and Spire Gulf are either currently being recovered in rates or are probable of recovery in future rates. The following table presents a reconciliation of the beginning and ending balances of asset retirement obligations at September 30, as reported in the balance sheets. Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Asset retirement obligations, beginning of year $ 206.4 $ 159.2 $ 75.2 $ 72.4 $ 120.1 $ 86.6 Liabilities incurred during the period 5.5 4.1 0.3 1.2 5.2 2.9 Liabilities settled during the period (4.6 ) (9.5 ) (1.1 ) (1.9 ) (1.9 ) (6.8 ) Accretion 9.1 13.2 3.6 3.5 5.0 9.7 Revisions in estimated cash flows 80.2 27.5 80.6 — — 27.7 Addition of Spire EnergySouth asset retirement obligations — 11.9 — — — — Asset retirement obligations, end of year $ 296.6 $ 206.4 $ 158.6 $ 75.2 $ 128.4 $ 120.1 REGULATED OPERATIONS – The Utilities account for their regulated operations in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 980, “Regulated Operations.” This Topic sets forth the application of GAAP for those companies whose rates are established by or are subject to approval by an independent third-party regulator. The provisions of this accounting guidance require, among other things, that financial statements of a regulated enterprise reflect the actions of regulators, where appropriate. These actions may result in the recognition of revenues and expenses in time periods that are different than non-regulated enterprises. When this occurs, costs are deferred as assets in the balance sheet (regulatory assets) and recorded as expenses when those amounts are reflected in rates. In addition, regulators can impose liabilities upon a regulated company for amounts previously collected from customers and for recovery of costs that are expected to be incurred in the future (regulatory liabilities). Management believes that the current regulatory environment supports the continued use of these regulatory accounting principles and that all regulatory assets and regulatory liabilities are recoverable or refundable through the regulatory process. See additional discussion on regulated operations in Note 15 , Regulatory Matters. As discussed below for Spire Missouri and Spire Alabama, the Purchased Gas Adjustment (PGA) clauses and Gas Supply Adjustment (GSA) riders allow the Utilities to pass through to customers the cost of purchased gas supplies. Regulatory assets and regulatory liabilities related to the PGA clauses and the GSA rider are both labeled Unamortized Purchased Gas Adjustments herein. Spire Missouri As authorized by the MoPSC, the PGA clause allows Spire Missouri to flow through to customers, subject to prudence review by the MoPSC, the cost of purchased gas supplies. To better match customer billings with market natural gas prices, Spire Missouri is allowed to file to modify, on a periodic basis, the level of gas costs in its PGA. Certain provisions of the PGA clause are included below: • Spire Missouri has a risk management policy that allows for the purchase of natural gas derivative instruments with the goal of managing price risk associated with purchasing natural gas on behalf of its customers. The MoPSC clarified that costs, cost reductions, and carrying costs associated with the Utility’s use of natural gas derivative instruments are gas costs recoverable through the PGA mechanism. • The tariffs allow Spire Missouri flexibility to make up to three discretionary PGA changes during each year, in addition to its mandatory November PGA change, so long as such changes are separated by at least two months . • Spire Missouri is authorized to apply carrying costs to all over- or under-recoveries of gas costs, including costs and cost reductions associated with the use of derivative instruments, including cash payments for margin deposits. Spire Missouri East is also authorized to recover gas inventory carrying costs through its PGA rates to recover costs it incurs to finance its investment in gas supplies that are purchased during the storage injection season for sale during the heating season. • The MoPSC approved a plan applicable to Spire Missouri’s gas supply commodity costs under which it retains a portion of cost savings associated with the acquisition of natural gas below an established benchmark level. This gas supply cost management program allows Spire Missouri to retain 10% of cost savings, up to a maximum of $3.0 annually. Spire Missouri did not record any such incentive compensation under the plan during the three fiscal years reported. Incentives recorded under the plan, if any, are included in Gas Utility Operating Revenues on the Consolidated Statements of Income and under Operating Revenues on Spire Missouri’s Statements of Income. Pursuant to the provisions of the PGA clause, the difference between actual costs incurred and costs recovered through the application of the PGA clause are reflected as a deferred charge or credit at the end of the fiscal year. These costs include costs and cost reductions associated with the use of derivative instruments and gas inventory carrying costs, amounts due to or from customers related to operation of the gas supply cost management program, refunds received from the Company’s suppliers in connection with gas supply, transportation, and storage services, and carrying costs on such over- or under-recoveries. At that time, the balance is classified as a current asset or current liability and recovered from, or credited to, customers over an annual period commencing in November. The balance in the current account is amortized as amounts are reflected in customer billings. The PGA clause also provides for the treatment of income from off-system sales and capacity release revenues. Pre-tax income from off-system sales and capacity release revenues is shared with customers, with an estimated amount assumed in PGA rates. The difference between the actual amount allocated to customers for each fiscal year and the estimated amount assumed in PGA rates is recovered from, or credited to, customers over an annual period commencing in the subsequent November. The customer share of such income is determined in accordance with the following tables, shown for each service territory for which the PGA clauses were approved by the MoPSC. Customer Share Company Share Spire Missouri East First $2.0 of pre-tax income* 85% 15% Next $2.0 of pre-tax income 80% 20% Next $2.0 of pre-tax income 75% 25% Amounts of pre-tax income exceeding $6.0 70% 30% * Customer share was set to 85% and company share set to 15% in fiscal 2017. For fiscal 2016 and 2015, the customer share and company share were 100% and 0%, respectively. Spire Missouri West First $1.2 of pre-tax income 85% 15% Next $1.2 of pre-tax income 80% 20% Next $1.2 of pre-tax income 75% 25% Amounts of pre-tax income exceeding $3.6 70% 30% Spire Alabama Spire Alabama’s rate schedules for natural gas distribution charges contain a GSA rider, established in 1993, which permits the pass-through to customers of changes in the cost of gas supply. Spire Alabama’s tariff provides a temperature adjustment mechanism, also included in the GSA rider, which is designed to moderate the impact of departures from normal temperatures on Spire Alabama’s earnings. The temperature adjustment applies primarily to residential, small commercial and small industrial customers. Other non-temperature weather-related conditions that may affect customer usage are not included in the temperature adjustment. NATURAL GAS AND PROPANE GAS – For Spire Missouri East, inventory of natural gas in storage is priced on a last in, first out (LIFO) basis and inventory of propane gas in storage is priced on a first in, first out (FIFO) basis. For the rest of the Gas Utility segment, inventory of natural gas in storage is priced on the weighted average cost basis. The replacement cost of Spire Missouri’s natural gas for current use in eastern Missouri at September 30, 2017 and September 30, 2016 was less than the LIFO cost by $20.8 and $11.4 , respectively. The carrying value of the Utilities’ inventory is not adjusted to the lower of cost or market prices because, pursuant to PGA or GSA, actual gas costs are recovered in customer rates. Natural gas and propane gas storage inventory in Spire’s other operating segments is recorded at the lower of average cost or market. BUSINESS COMBINATIONS – The Spire EnergySouth acquisition was accounted for by Spire using business combination accounting. Under this method, the purchase price paid by the acquirer is allocated to the assets acquired and liabilities assumed as of the acquisition date based on their fair value. For additional information on the acquisition of Spire EnergySouth, refer to Note 2 , Acquisitions. GOODWILL – Goodwill is measured as the excess of the acquisition-date fair value of the consideration transferred over the amount of acquisition-date identifiable assets acquired net of assumed liabilities. Spire and Spire Missouri evaluate goodwill for impairment as of July 1 of each year, or more frequently if events and circumstances indicate that goodwill might be impaired. At July 1, 2017, 2016 and 2015, Spire and Spire Missouri each applied a quantitative goodwill evaluation model to their reporting units and concluded goodwill was not impaired because the fair value exceeded the carrying amount. The changes in the carrying amount of goodwill by reportable segment were as follows: Gas Utility Gas Marketing Other Total Balance as of September 30, 2014 $ 210.2 $ — $ 727.6 $ 937.8 Adjustments to finalize the acquisition of Spire Alabama — — 8.2 8.2 Balance as of September 30, 2015 210.2 — 735.8 946.0 Acquisition of Spire EnergySouth — — 218.9 218.9 Balance as of September 30, 2016 210.2 — 954.7 1,164.9 Adjustments to finalize the acquisition of Spire EnergySouth — — 6.7 6.7 Balance as of September 30, 2017 $ 210.2 $ — $ 961.4 $ 1,171.6 IMPAIRMENT OF LONG-LIVED ASSETS – Long-lived assets classified as held and used are evaluated for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. Whether impairment has occurred is determined by comparing the estimated undiscounted cash flows attributable to the assets with the carrying value of the assets. If the carrying value exceeds the undiscounted cash flows, the Company recognizes an impairment charge equal to the amount of the carrying value that exceeds the estimated fair value of the assets. In the period in which the Company determines an asset meets held-for-sale criteria, an impairment charge is recorded to the extent the book value exceeds its fair value less cost to sell. REVENUE RECOGNITION – The Utilities read meters and bill customers on monthly cycles. The Missouri Utilities, Spire Gulf and Spire Mississippi record their gas utility revenues from gas sales and transportation services on an accrual basis that includes estimated amounts for gas delivered, but not yet billed. The accruals for unbilled revenues are reversed in the subsequent accounting period when meters are actually read and customers are billed. The amounts of accrued unbilled revenues for Spire Missouri at September 30, 2017 and 2016 were $30.1 and $26.1 , respectively. Spire Alabama records natural gas distribution revenues in accordance with the tariff established by the APSC. Unbilled revenue is accrued in an amount equal to the related gas cost, as profit margin is not considered earned until billed. The amounts of accrued unbilled revenues for Spire Alabama at September 30, 2017 and 2016 were $1.9 and $5.9 . Spire’s other subsidiaries, including Spire Marketing, record revenues when earned, either when the product is delivered or when services are performed. In the course of its business, Spire Marketing enters into commitments associated with the purchase or sale of natural gas. Certain of its derivative natural gas contracts are designated as normal purchases or normal sales and, as such, are excluded from the scope of ASC Topic 815, “Derivatives and Hedging.” Those contracts are accounted for as executory contracts and recorded on an accrual basis. Revenues and expenses from such contracts are recorded using a gross presentation. Contracts not designated as normal purchases or normal sales are recorded as derivatives with changes in fair value recognized in earnings in the periods prior to physical delivery. For additional information on derivative instruments, refer to Note 10 , Derivative Instruments and Hedging Activities. Certain of Spire Marketing’s wholesale purchase and sale transactions are classified as trading activities for financial reporting purposes. Under GAAP, revenues and expenses associated with trading activities are presented on a net basis in Gas Marketing operating revenues (or expenses, if negative) in the Consolidated Statements of Income. This net presentation has no effect on operating income or net income. INCOME TAXES – Spire and its subsidiaries account for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amount of existing assets and liabilities and the respective tax basis and for tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effects on deferred tax assets and liabilities of a change in enacted tax rates is recognized in income or loss for a non-regulated company, and in a regulatory asset or regulatory liability for a regulated company. A valuation allowance is established when it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions in accordance with authoritative guidance. The authoritative guidance addresses the determination of whether tax benefits claimed, or expected to be claimed, on a tax return should be recorded in the financial statements. Spire may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the position will be sustained upon examination by the taxing authority, based on the technical merits of the position. Tax-related interest and penalties, if any, are classified as a liability on the balance sheets. CASH AND CASH EQUIVALENTS – All highly liquid debt instruments purchased with original maturities of three months or less are considered to be cash equivalents. Such instruments are carried at cost, which approximates market value. Outstanding checks on the Company’s and Utilities’ bank accounts in excess of funds on deposit create book overdrafts (which are funded at the time checks are presented for payment) and are classified as Other in the Current Liabilities section of the balance sheets. Changes in book overdrafts are reflected as Operating Activities in the statements of cash flows. NATURAL GAS RECEIVABLE – Spire Marketing enters into natural gas transactions with natural gas pipeline companies known as park and loan arrangements. Under the terms of the arrangements, Spire Marketing purchases natural gas from a third party and delivers that natural gas to the pipeline company for the right to receive the same quantity of natural gas from the pipeline company at the same location in a future period. These arrangements are accounted for as non-monetary transactions under GAAP and are recorded at the carrying amount. As such, natural gas receivables are reflected on the Consolidated Balance Sheets at cost, which includes related pipeline fees associated with the transactions. In the period that the natural gas is returned to Spire Marketing, concurrent with the sale of the natural gas to a third party, the related natural gas receivable is expensed in the Consolidated Statements of Income. In conjunction with these transactions, Spire Marketing usually enters into New York Mercantile Exchange (NYMEX) and Intercontinental Exchange (ICE) natural gas futures, options, and swap contracts or fixed price sales agreements to protect against market changes in future sales prices. EARNINGS PER COMMON SHARE – GAAP requires dual presentation of basic and diluted earnings per share (EPS). EPS is computed using the two-class method, which is an earnings allocation method for computing EPS that treats a participating security as having rights to earnings that would otherwise have been available to common shareholders. Certain of the Company’s stock-based compensation awards pay non-forfeitable dividends to the participants during the vesting period and, as such, are deemed participating securities. Basic EPS is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. Diluted EPS is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding that are increased for additional shares that would be outstanding if potentially dilutive non-participating securities were converted to common shares, pursuant to the treasury stock method. Shares attributable to equity units, non-participating stock options and time-vested restricted stock/units are excluded from the calculation of diluted earnings per share if the effect would be antidilutive. Shares attributable to non-participating performance-contingent restricted stock awards are only included in the calculation of diluted earnings per share to the extent the underlying performance and/or market conditions are satisfied (a) prior to the end of the reporting period or (b) would be satisfied if the end of the reporting period were the end of the related contingency period and the result would be dilutive. The Company’s EPS computations are presented in Note 4 , Earnings Per Common Share. GROSS RECEIPTS AND SALES TAXES – Gross receipts taxes associated with the Company’s natural gas utility services are imposed on the Company, Spire Missouri, and Spire Alabama and billed to its customers. The revenue and expense amounts are recorded gross in the “Operating Revenues” and “Taxes, other than income taxes” lines, respectively, in the statements of income. The following table presents gross receipts taxes recorded as revenues: 2017 2016 2015 Spire $ 84.6 $ 75.5 $ 97.3 Spire Missouri 60.7 57.4 74.5 Spire Alabama 19.5 17.9 22.6 Sales taxes imposed on applicable Spire Alabama and Spire Missouri sales are billed to customers. These amounts are not recorded in the statements of income but are recorded as tax collections payable and included in the “Other” line of the Current Liabilities section of the balance sheets. TRANSACTIONS WITH AFFILIATES – Transactions between affiliates of the Company have been eliminated from the consolidated financial statements of Spire. Spire Missouri and Spire Alabama borrowed funds from the Company and incurred related interest, as reflected in their separate financial statements, and participated in normal intercompany shared services transactions. In addition, Spire Missouri’s other transactions with affiliates included: 2017 2016 2015 Purchases of natural gas from Spire Marketing $ 74.4 $ 46.3 $ 74.1 Sales of natural gas to Spire Marketing 7.8 1.9 4.0 Transportation services received from Spire NGL Inc. 1.0 1.0 1.0 ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS – Trade accounts receivable are recorded at the amounts due from customers, including unbilled amounts. Estimates of the collectability of trade accounts receivable are based on historical trends, age of receivables, economic conditions, credit risk of specific customers, and other factors. Accounts receivable are written off against the allowance for doubtful accounts when they are deemed to be uncollectible. Spire’s provision for uncollectible accounts includes the amortization of previously deferred uncollectible expenses for Spire Missouri and Spire Alabama, as approved by the MoPSC and the APSC, respectively. FINANCE RECEIVABLES – Spire Alabama finances third party contractor sales of merchandise including gas furnaces and appliances. At September 30, 2017 and September 30, 2016 , the Company’s finance receivable totaled approximately $12.5 and $11.8 , respectively. Financing is available only to qualified customers who meet creditworthiness thresholds for customer payment history and external agency credit reports. Spire Alabama relies upon ongoing payments as the primary indicator of credit quality during the term of each contract. The allowance for credit losses is recognized using an estimate of write-off percentages based on historical experience applied to an aging of the finance receivable balance. Delinquent accounts are evaluated on a case-by-case basis and, absent evidence of debt repayment, after 90 days are due in full and assigned to a third-party collection agency. The remaining finance receivable is written off approximately 12 months after being assigned to the third-party collection agency. Spire Alabama had finance receivables past due 90 days or more of $0.4 at September 30, 2017 and September 30, 2016 . Spire Alabama recorded a related allowance for credit losses at September 30, 2017 and September 30, 2016 of $0.4 . GROUP MEDICAL AND WORKERS’ COMPENSATION RESERVES – The Company self-insures its group medical and workers’ compensation costs and carries stop-loss coverage in relation to medical claims and workers’ compensation claims. Reserves for amounts incurred but not reported are established based on historical cost levels and lags between occurrences and reporting. FAIR VALUE MEASUREMENTS – Certain assets and liabilities are recognized or disclosed at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). GAAP establishes a fair value hierarchy that prioritizes the inputs used to measure fair value. The levels of the hierarchy are described below: • Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities. • Level 2 – Pricing inputs other than quoted prices included within Level 1, which are either directly or indirectly observable for the asset or liability as of the reporting date. These inputs are derived principally from, or corroborated by, observable market data. • Level 3 – Pricing that is based upon inputs that are generally unobservable that are based on the best information available and reflect management’s assumptions about how market participants would price the asset or liability. Assessment of the significance of a particular input to the fair value measurements may require judgment and may affect the valuation of the asset or liability and its placement within the fair value hierarchy. Additional information about fair value measurements is provided in Note 8 , Fair Value of Financial Instruments, Note 9 , Fair Value Measurements, and Note 13 , Pension Plans and Other Postretirement Benefits. STOCK-BASED COMPENSATION – The Company measures stock-based compensation awards at fair value at the date of grant and recognizes the compensation cost of the awards over the requisite service period. Effective with the adoption of Accounting Standards Update No. 2016-09 at the beginning of fiscal 2017 (described under New Accounting Pronouncements below), forfeitures are recognized in the period they occur. In fiscal 2016 and fiscal 2015, forfeitures were estimated at the time of grant and revised, when necessary, in subsequent periods when the actu

ACQUISITIONS

ACQUISITIONS	12 Months Ended
ACQUISITIONS	Sep. 30, 2017
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS Effective September 12, 2016, Spire completed the acquisition of 100% of the common stock of Spire EnergySouth, the parent company of Spire Gulf and Spire Mississippi, serving natural gas utility customers in Alabama and Mississippi. This acquisition is supportive of the strategic focus on growing Spire’s gas utility business and creating geographic and regulatory diversity. Total cash consideration paid, net of cash acquired, debt assumed, and a working capital settlement payment received, was $313.9 . The goodwill of $225.6 arising from this acquisition, which is not deductible for tax purposes, is attributable to the assembled workforce and the expected cost efficiencies and strategic benefits of the transaction. The Company did not elect pushdown accounting, so the goodwill was recorded on the Spire parent company balance sheet rather than the Spire EnergySouth subsidiary balance sheet and is included in disclosures of segment assets under Other. The following table summarizes the consideration paid and the amounts of the assets acquired and liabilities assumed at the acquisition date. As originally recorded Measurement period adjustments As adjusted Recognized amounts of identifiable assets acquired and liabilities assumed: Utility plant $ 199.5 $ — $ 199.5 Cash 2.0 — 2.0 Other current assets 17.5 0.2 17.7 Other assets 79.8 (10.7 ) 69.1 Long-term debt (67.0 ) — (67.0 ) Other current liabilities (42.7 ) — (42.7 ) Deferred tax liabilities (35.5 ) — (35.5 ) Other liabilities (52.8 ) — (52.8 ) Total identifiable net assets 100.8 (10.5 ) 90.3 Goodwill 218.9 6.7 225.6 Consideration (cash) $ 319.7 $ (3.8 ) $ 315.9 Spire EnergySouth’s results of operations are included in the Spire statements of income from the date of acquisition, as shown in the following table. 2017 2016 Total Operating Revenues $ 95.5 $ 3.3 Net Income (Loss) 9.4 (0.2 ) Earnings Per Share $ 0.20 $ — The following unaudited pro forma financial information presents Spire’s combined results of operations as though the Spire EnergySouth acquisition had occurred as of the beginning of fiscal 2015. The unaudited pro forma financial information is not necessarily indicative of either future results of operations or results that would have been achieved if the acquisition had occurred as of the earlier date. It includes estimates and assumptions which management believes are reasonable. The timing of integration costs was not changed. 2017 2016 2015 Total Operating Revenues $ 1,740.7 $ 1,632.4 $ 2,081.6 Net Income 161.6 153.9 143.6 Basic Earnings Per Share $ 3.44 $ 3.48 $ 3.32 Diluted Earnings Per Share 3.43 3.46 3.31

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
STOCK-BASED COMPENSATION	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Spire’s 2015 incentive plan, The Laclede Group 2015 Equity Incentive Plan (the 2015 Plan), was approved at the annual meeting of shareholders of Spire on January 29, 2015. The purpose of the 2015 Plan is to encourage directors, officers, and employees of the Company and its subsidiaries to contribute to the Company’s success and align their interests with that of shareholders. To accomplish this purpose, the Compensation Committee (Committee) of the Board of Directors may grant awards under the 2015 Plan that may be earned by achieving performance objectives and/or other criteria as determined by the Committee. Under the terms of the 2015 Plan, officers and employees of the Company and its subsidiaries, as determined by the Committee, are eligible to be selected for awards. The 2015 Plan provides for restricted stock, restricted stock units, qualified and non-qualified stock options, stock appreciation rights, and performance shares payable in stock, cash, or a combination of both. The 2015 Plan generally provides a minimum vesting period of at least three years for each type of award, with pro rata vesting permitted during the minimum three -year vesting period. The maximum number of shares reserved for issuance under the 2015 Plan is 1,000,000 . The 2015 Plan replaced The Laclede Group 2006 Equity Incentive Plan (the 2006 Plan), which in turn replaced The Laclede Group, Inc. 2002 Equity Incentive Plan (the 2002 Plan). Shares reserved under the 2006 Plan and the 2002 Plan, other than those needed for outstanding awards, were canceled upon shareholder approval of the 2015 Plan. The Company issues new shares to satisfy employee restricted stock awards and stock option exercises. Restricted Stock Awards During fiscal 2017 , the Company granted 196,400 performance-contingent restricted share units to executive officers and key employees at a weighted average grant date fair value of $45.01 per share. This number represents the maximum shares that can be earned pursuant to the terms of the awards. The share units have a performance period ending September 30, 2019. While the participants have no interim voting rights on these share units, dividends accrue during the performance period and are paid to the participants upon vesting, but are subject to forfeiture if the underlying share units do not vest. The number of share units that will ultimately vest is dependent upon the attainment of certain levels of earnings and other strategic goals, as well as the Company’s level of total shareholder return (TSR) during the performance period relative to a comparator group of companies. This TSR provision is considered a market condition under GAAP and is discussed further below. The weighted average grant date fair value of performance-contingent restricted shares and share units granted during fiscal years 2016 and 2015 was $45.95 and $36.69 per share, respectively. Fiscal 2017 activity of restricted stock and restricted stock units subject to performance and/or market conditions is presented below: Shares/ Units Weighted Average Grant Date Fair Value Per Share Nonvested at September 30, 2016 510,583 $ 40.37 Granted (maximum shares that can be earned) 196,400 $ 45.01 Vested (78,825 ) $ 42.37 Forfeited (64,128 ) $ 33.03 Nonvested at September 30, 2017 (at maximum) 564,030 $ 42.51 Nonvested at September 30, 2017 (at target) 282,015 $ 56.32 During fiscal 2017 , the Company granted 33,240 shares of time-vested restricted stock to executive officers and key employees at a weighted average grant date fair value of $63.05 per share. Unless forfeited based on terms of the agreements, these shares will vest in fiscal 2020. In the interim, participants receive full voting rights and dividends, which are not subject to forfeiture. The weighted average grant date fair value of time-vested restricted stock and restricted stock units awarded to employees during fiscal years 2016 and 2015 was $59.40 and $50.90 per share, respectively. During fiscal 2017 , the Company granted 10,850 shares of time-vested restricted stock to non-employee directors at a weighted average grant date fair value of $63.45 per share. These shares vested in fiscal 2017, six months after the grant date. The weighted average grant date fair value of restricted stock awarded to non-employee directors during fiscal years 2016 and 2015 was $63.93 and $54.66 per share, respectively. Time-vested restricted stock and stock unit activity for fiscal 2017 is presented below: Shares/ Units Weighted Average Grant Date Fair Value Per Share Nonvested at September 30, 2016 132,779 $ 49.83 Granted 44,090 $ 63.15 Vested (58,200 ) $ 47.67 Forfeited (7,729 ) $ 55.58 Nonvested at September 30, 2017 110,940 $ 55.85 For restricted stock and stock units (performance-contingent and time-vested) that vested during fiscal years 2017, 2016, and 2015, the Company withheld 35,514 shares, 30,712 shares, and 31,688 , respectively, at weighted average prices of $63.83 , $57.29 , and $50.65 per share, respectively, pursuant to elections by employees to satisfy tax withholding obligations. The total fair value of restricted stock (performance-contingent and time-vested) that vested during fiscal years 2017 , 2016 , and 2015 was $8.9 , $6.3 , and $6.4 , respectively, and the related tax benefit was $3.3 , $2.4 , and $2.4 , respectively. None of the tax benefits have been realized. Stock Option Awards No stock options were granted during fiscal years 2017 , 2016 , and 2015 . There was no stock option activity in fiscal 2017, as all outstanding stock options either vested or forfeited in fiscal 2016. During fiscal 2016 , cash received from the exercise of stock options was $0.7 and the related intrinsic value was $0.7 . During fiscal 2015 , cash received from the exercise of stock options was $1.5 and the related intrinsic value was $0.9 . Related tax benefits were not material in any of those years. Equity Compensation Costs Compensation cost for performance-contingent restricted stock and stock unit awards is based upon the probable outcome of the performance conditions. For shares or units that do not vest or that are not expected to vest due to the outcome of the performance conditions (excluding market conditions), no compensation cost is recognized and any previously recognized compensation cost is reversed. The fair value of awards of performance-contingent and time-vested restricted stock and restricted stock units, not subject to the TSR provision, are estimated using the closing price of the Company’s stock on the grant date. For those awards that do not pay dividends during the vesting period, the estimate of fair value is reduced by the present value of the dividends expected to be paid on the Company’s common stock during the performance period, discounted using an appropriate United States (US) Treasury yield. For shares subject to the TSR provision, the estimated impact of this market condition is reflected in the grant date fair value per share of the awards. Accordingly, compensation cost is not reversed to reflect any actual reductions in the awards that may result from the TSR provision. However, if the Company’s TSR during the performance period ranks below the level specified in the award agreements, relative to a comparator group of companies, and the Committee elects not to reduce the award (or reduce by a lesser amount), this election would be accounted for as a modification of the original award and additional compensation cost would be recognized at that time. The grant date fair value of the awards subject to the TSR provision awarded during fiscal years 2017 , 2016 , and 2015 was valued by a Monte Carlo simulation model that assessed the probabilities of various TSR outcomes. The significant assumptions used in the Monte Carlo simulations are as follows: 2017 2016 2015 Risk-free interest rate 1.39% 1.14% 0.83% Expected dividend yield of stock — — — Expected volatility of stock 16.3% 15.0% 14.0% Vesting period 2.8 years 2.8 years 2.8 years The risk-free interest rate was based on the yield on US Treasury securities matching the vesting period. A zero percent dividend yield was used, which is mathematically equivalent to the assumption that dividends are reinvested as they are paid. The expected volatility is based on the historical volatility of the Company’s stock. Volatility assumptions were also made for each of the companies included in the comparator group. The vesting period is equal to the performance period set forth in the terms of the award. The amounts of compensation cost recognized for share-based compensation arrangements are presented below: 2017 2016 2015 Total compensation cost $ 7.4 $ 6.7 $ 6.7 Compensation cost capitalized (3.3 ) (2.2 ) (1.8 ) Compensation cost recognized in net income $ 4.1 $ 4.5 $ 4.9 Income tax benefit recognized in net income (1.5 ) (1.7 ) (1.9 ) Compensation cost recognized in net income, net of income tax $ 2.6 $ 2.8 $ 3.0 As of September 30, 2017 , there was $8.9 of total unrecognized compensation cost related to non-vested share-based compensation arrangements. That cost is expected to be recognized over a weighted average period of 1.8 years .

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	12 Months Ended
EARNINGS PER COMMON SHARE	Sep. 30, 2017
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	EARNINGS PER COMMON SHARE 2017 2016 2015 Basic EPS: Net Income $ 161.6 $ 144.2 $ 136.9 Less: Income allocated to participating securities 0.4 0.5 0.5 Net Income Available to Common Shareholders $ 161.2 $ 143.7 $ 136.4 Weighted Average Shares Outstanding (millions) 46.9 44.1 43.2 Earnings Per Share of Common Stock $ 3.44 $ 3.26 $ 3.16 Diluted EPS: Net Income $ 161.6 $ 144.2 $ 136.9 Less: Income allocated to participating securities 0.4 0.5 0.5 Net Income Available to Common Shareholders $ 161.2 $ 143.7 $ 136.4 Weighted Average Shares Outstanding (millions) 46.9 44.1 43.2 Dilutive Effect of Stock Options, Restricted Stock, and Restricted Stock Units (millions) 0.1 0.2 0.1 Weighted Average Diluted Shares (millions) 47.0 44.3 43.3 Earnings Per Share of Common Stock $ 3.43 $ 3.24 $ 3.16 Outstanding Shares (in millions) Excluded from the Calculation of Diluted EPS Attributable to: Restricted stock and stock units subject to performance and/or market conditions 0.5 0.3 0.3 Spire’s 2.875 million equity units issued in June 2014 were anti-dilutive for the periods they were outstanding. Accordingly, they were also excluded from the calculation of weighted average diluted shares for those periods. On April 3, 2017, Spire settled the purchase contracts underlying those equity units by issuing approximately 2.5 million shares of its common stock. See Note 5 for more information.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
STOCKHOLDERS' EQUITY	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
STOCKHOLDERS' EQUITY	SHAREHOLDERS’ EQUITY Spire In 2014, Spire issued 2.875 million equity units as a portion of the Spire Alabama acquisition financing. The equity units were originally issued at $50 per unit pursuant to the Purchase Contract and Pledge Agreement (Purchase Contract) dated as of June 11, 2014 between Spire and U.S. Bank National Association, as purchase contract agent, collateral agent, custodial agent and securities intermediary. These units consisted of $143.8 aggregate principal amount of 2014 Series A 2.00% remarketable junior subordinated notes due 2022 and the Purchase Contract obligating the holder to purchase common shares at a future settlement date. The equity unit investments were effectively replaced as planned in a series of transactions outlined in Note 6 , resulting in the issuance of 2,504,684 shares of the Company’s common stock at a purchase price of $57.3921 per share. Under the contract terms, the equity units were converted to common stock at the rate of 0.8712 shares per unit, with a corresponding adjustment to purchase price. Spire filed a registration statement on Form S-3 with the US Securities and Exchange Commission (SEC) on June 15, 2017 for the issuance and sale of up to 250,000 shares of its common stock under its Dividend Reinvestment and Direct Stock Purchase Plan. There were 244,130 and 239,945 shares at September 30, 2017 and November 10, 2017 , respectively, remaining available for issuance under this Form S-3. On May 17, 2016, Spire completed a public offering of 2,185,000 shares of its common stock, generating $133.2 of proceeds net of issuance costs. On September 23, 2016, Spire and Spire Missouri filed with the SEC a joint shelf registration statement on Form S-3 for issuance of various types of debt and equity securities, which registration statement will expire September 22, 2019. The amount, timing, and type of additional financing to be issued under this shelf registration statement will depend on cash requirements and market conditions. At September 30, 2017 and 2016 , Spire had authorized 5,000,000 shares of preferred stock, but none were issued and outstanding. Spire Missouri Substantially all of Spire Missouri’s plant is subject to the liens of its first mortgage bonds. The mortgage contains several restrictions on Spire Missouri’s ability to pay cash dividends on its common stock or to make loans to its parent company. These mortgage restrictions are applicable regardless of whether the stock is publicly held or held solely by Spire Missouri’s parent company. Under the most restrictive of these provisions, no cash dividend may be declared or paid if, after the dividend, the aggregate net amount spent for all dividends after September 30, 1953 would exceed a maximum amount determined by a formula set out in the mortgage. Under that formula, the maximum amount is the sum of $8.0 plus earnings applicable to common stock (adjusted for stock repurchases and issuances) for the period from September 30, 1953 to the last day of the quarter before the declaration or payment date for the dividends. As of September 30, 2017 and 2016 , the amount under the mortgage’s formula that was available to pay dividends was $1,010.8 and $916.8 , respectively. Thus, all of Spire Missouri’s retained earnings were free from such dividend restrictions as of those dates. On September 23, 2016, Spire and Spire Missouri filed with the SEC a joint shelf registration statement on Form S-3 for issuance of various types of debt and equity securities, which registration statement will expire September 22, 2019. The amount, timing, and type of additional financing to be issued under this shelf registration statement will depend on cash requirements and market conditions, as well as future MoPSC authorizations. Spire Missouri has authority from the MoPSC to issue debt securities and preferred stock, including on a private placement basis, as well as to issue common stock, receive paid-in capital, and enter into capital lease agreements, all for a total of up to $300.0 . On September 15, 2017, Spire Missouri issued $170.0 in first mortgage bonds, leaving $130.0 available under the MoPSC authorization. At September 30, 2017 and 2016 , Spire Missouri had authorized 1,480,000 shares of preferred stock, but none were issued and outstanding. Spire Alabama At September 30, 2017 and 2016 , Spire Alabama had authorized 120,000 shares of preferred stock, but none were issued and outstanding. Other Comprehensive Income The components of accumulated other comprehensive income (loss), net of income taxes, recognized in the balance sheets at September 30 were as follows: Net Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Pension and Other Postretirement Benefit Plans Net Unrealized Losses on Available for Sale Securities Total Spire Balance at September 30, 2015 $ (0.4 ) $ (1.5 ) $ (0.1 ) $ (2.0 ) Other comprehensive loss (1.9 ) (0.3 ) — (2.2 ) Balance at September 30, 2016 (2.3 ) (1.8 ) (0.1 ) (4.2 ) Other comprehensive income (loss) 7.2 0.3 (0.1 ) 7.4 Balance at September 30, 2017 $ 4.9 $ (1.5 ) $ (0.2 ) $ 3.2 Spire Missouri Balance at September 30, 2015 (0.2 ) (1.5 ) — $ (1.7 ) Other comprehensive income (loss) 0.3 (0.3 ) (0.1 ) (0.1 ) Balance at September 30, 2016 0.1 (1.8 ) (0.1 ) (1.8 ) Other comprehensive income (loss) — 0.2 (0.1 ) 0.1 Balance at September 30, 2017 $ 0.1 $ (1.6 ) $ (0.2 ) $ (1.7 ) Income tax expense (benefit) recorded for items of other comprehensive income (loss) reported in the statements of comprehensive income is calculated by applying statutory federal, state, and local income tax rates applicable to ordinary income. The tax rates applied to individual items of other comprehensive income (loss) are similar within each reporting period. For the periods presented, Spire Alabama had no accumulated other comprehensive income (loss) balances.

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
LONG-TERM DEBT	Sep. 30, 2017
Debt Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT Composition of long-term debt for Spire, Spire Missouri and Spire Alabama are shown in each registrant’s statements of capitalization as part of the financial statements. Maturities of long-term debt for Spire on a consolidated basis, Spire Missouri and Spire Alabama for the five fiscal years subsequent to September 30, 2017 are as follows: Spire Spire Missouri Spire Alabama 2018 $ 100.0 $ 100.0 $ — 2019 180.0 50.0 — 2020 40.0 — 40.0 2021 55.0 — — 2022 50.0 — 50.0 Spire’s, Spire Missouri’s and Spire Alabama’s short-term credit facilities and long-term debt agreements contain customary covenants and default provisions. As of September 30, 2017 , there were no events of default under these covenants. The Company’s, Spire Missouri’s and Spire Alabama’s access to capital markets, including the commercial paper market, and their respective financing costs, may depend on the credit rating of the entity that is accessing the capital markets. The credit ratings of the Company, Spire Missouri and Spire Alabama remain at investment grade, but are subject to review and change by the rating agencies. It is management’s view that the Company, Spire Missouri and Spire Alabama have adequate access to capital markets and will have sufficient capital resources, both internal and external, to meet anticipated capital requirements, which primarily include capital expenditures, interest payments on long-term debt, scheduled maturities of long-term debt, short-term seasonal needs, and dividends. Spire On March 10, 2017, Spire redeemed in full at par its $250.0 floating rate notes due August 15, 2017, plus accrued and unpaid interest. On March 15, 2017, Spire completed the issuance and sale of $100.0 in aggregate principal amount of Senior Notes due March 15, 2027. The notes bear interest at the rate of 3.93% per annum, payable semi-annually. The notes are senior unsecured obligations of the Company. The Company used the proceeds from the sale of the notes for the repayment of other debt. In 2014, Spire issued 2.875 million equity units as a portion of the Spire Alabama acquisition financing. The equity units were originally issued at $50 per unit pursuant to the Purchase Contract dated as of June 11, 2014 between Spire and U.S. Bank National Association, as purchase contract agent, collateral agent, custodial agent and securities intermediary. These units consisted of $143.8 aggregate principal amount of 2014 Series A 2.00% remarketable junior subordinated notes due 2022 (the Junior Notes) and the Purchase Contract obligating the holder to purchase common shares at a future settlement date. The equity unit investments were effectively replaced as planned in a series of transactions outlined below: • On February 22, 2017, the selling securityholders (as defined below) agreed to purchase the Junior Notes in connection with the remarketing of the junior subordinated notes that comprised a component of the equity units. • On the same day, Spire entered two related agreements: (1) a Securities Purchase and Registration Rights Agreement (the SPRRA), among Spire and the several purchasers named therein (the selling securityholders), obligating the selling securityholders to sell the Junior Notes to Spire in exchange for $143.8 aggregate principal amount of Spire’s 3.543% Senior Notes due 2024 (the Senior Notes) and a cash payment, and (2) an underwriting agreement with the selling securityholders and the several underwriters named therein in connection with the public offering of $150.0 aggregate principal amount of Senior Notes consisting of $6.2 principal amount of the Senior Notes issued and sold by Spire and $143.8 principal amount of the Senior Notes sold by the selling securityholders. The SPRRA granted the selling securityholders the right to offer the Senior Notes to the public in secondary public offerings. • The public offering was completed on February 27, 2017. Spire used its net proceeds from its sale of the Senior Notes to repay short-term debt. Spire did not receive any proceeds from the sale of the Senior Notes by the selling securityholders. • On April 3, 2017, Spire settled the Purchase Contracts underlying its 2.875 million equity units by issuing 2,504,684 shares of its common stock at a purchase price of $57.3921 per share. Fractional shares were settled in cash at $67.50 per share. The purchase price was funded with the proceeds from the Junior Notes. Under the contract terms, the equity units were converted to common stock at the rate of 0.8712 , with a corresponding adjustment to purchase price. Spire received net cash proceeds of approximately $142.0 , which it used to repay short-term debt incurred the previous month to redeem the floating rate notes. At September 30, 2017 , including the current portion but excluding unamortized discounts and debt issuance costs, Spire had long-term debt totaling $2,112.0 , of which $980.0 was issued by Spire Missouri, $250.0 was issued by Spire Alabama, and $67.0 was issued by other subsidiaries. All long-term debt bears fixed rates and is subject to changes in fair value as market interest rates change. However, increases and decreases in fair value would impact earnings and cash flows only if the Company were to reacquire any of these issues in the open market prior to maturity. Under GAAP applicable to the Utilities’ regulated operations, losses or gains on early redemption of long-term debt would typically be deferred as regulatory assets or regulatory liabilities and amortized over a future period. Of the Company’s $2,112.0 long-term debt (including the current portion), $25.0 has no call options, $1,037.0 has make-whole call options, $5.0 is callable currently, and $1,045.0 is callable at par one to six months prior to maturity. As indicated in Note 5 , Shareholders’ Equity, Spire has a shelf registration statement on Form S-3 on file with the SEC for the issuance of equity and debt securities. Including the current portion of long-term debt, the Company’s capitalization at September 30, 2017 consisted of 48.7% of common stock equity and 51.3% long-term debt, compared to 46.1% of common stock equity and 53.9% of long-term debt at September 30, 2016 . Spire Missouri On September 15, 2017, Spire Missouri issued and sold in a private placement $50.0 in aggregate principal amount of its first mortgage bonds due September 15, 2032, $70.0 in aggregate principal amount of its first mortgage bonds due September 15, 2047 and $50.0 in aggregate principal amount of its first mortgage bonds due September 15, 2057. Spire Missouri used the proceeds to refinance existing indebtedness and for other general corporate purposes. The 2032 bonds, 2047 bonds and 2057 bonds bear interest at a rate per annum of 3.68% , 4.23% and 4.38% , respectively, payable semi-annually on the 15th day of March and September of each year. Spire Missouri has authority from the MoPSC to issue debt securities and preferred stock, including on a private placement basis, as well as to issue common stock, receive paid-in-capital, and enter into capital lease agreements, all for a total of up to $300.0 for financings placed any time before September 30, 2018. During the year ended September 30, 2017 , Spire Missouri issued $170.0 in securities under this authorization, so as of that date, $130.0 remains available to be issued. At September 30, 2017 , including the current portion but excluding unamortized discounts and debt issuance costs, Spire Missouri had long-term debt totaling $980.0 . While these long-term debt issues are fixed-rate, they are subject to changes in fair value as market interest rates change. Of Spire Missouri’s $980.0 in long-term debt, $25.0 has no call options, $435.0 has make-whole call options and $520.0 is callable at par three to six months prior to maturity. As indicated in Note 5 , Shareholders’ Equity, Spire Missouri has a shelf registration on Form S-3 on file with the SEC for issuance of first mortgage bonds, unsecured debt, and preferred stock, which expires on September 22, 2019. Substantially all of Spire Missouri’s plant is subject to the liens of its first mortgage bonds. The mortgage contains several restrictions on Spire Missouri’s ability to pay cash dividends on its common stock, which are described in Note 5 , Shareholders’ Equity. Including the current portion of long-term debt, Spire Missouri’s capitalization at September 30, 2017 consisted of 54.6% of common stock equity and 45.4% long-term debt compared to 57.1% of common stock equity and 42.9% of long-term debt at September 30, 2016 . Spire Alabama At September 30, 2017 , excluding unamortized debt issuance costs, Spire Alabama had fixed-rate long-term debt totaling $250.0 . While these long-term debt issues are fixed-rate, they are subject to changes in fair value as market interest rates change. All of Spire Alabama’s $250.0 long-term debt has make-whole call options. Spire Alabama’s capitalization at September 30, 2017 consisted of 77.8% of common stock equity and 22.2% long-term debt, consistent with 77.8% of common stock equity and 22.2% of long-term debt at September 30, 2016 . Because Spire Alabama has no standing authority to issue long-term debt, it must petition the APSC for each planned issuance. On October 3, 2017, Spire Alabama received authorization and approval from the APSC to borrow up to $75.0 for general corporate purposes and to retire short-term debt.

NOTES PAYABLE AND CREDIT AGREEM

NOTES PAYABLE AND CREDIT AGREEMENTS	12 Months Ended
NOTES PAYABLE AND CREDIT AGREEMENTS	Sep. 30, 2017
Short-term Debt [Abstract]
NOTES PAYABLE AND CREDIT AGREEMENTS	NOTES PAYABLE AND CREDIT AGREEMENTS Short-term cash requirements outside of the Utilities have generally been funded by Spire or met with internally generated funds . The Utilities’ short term borrowing requirements typically peak during the colder months. Total short-term borrowing requirements can be met through the sale of commercial paper supported by a revolving credit facility or through direct use of the revolving credit facility. On December 14, 2016, Spire, Spire Missouri, and Spire Alabama entered into a new syndicated revolving credit facility pursuant to a loan agreement with 11 banks, expiring December 14, 2021. The largest portion provided by a single bank under the line is 12.3% . The loan agreement replaced Spire’s and Spire Missouri’s existing loan agreements dated as of September 3, 2013 and amended September 3, 2014, which were set to expire on September 3, 2019, and Spire Alabama’s existing loan agreement dated September 2, 2014, which was set to expire September 2, 2019. All three previous agreements were terminated on December 14, 2016. The loan agreement has an aggregate credit commitment of $975.0 , including sublimits of $300.0 for Spire, $475.0 for Spire Missouri, and $200.0 for Spire Alabama. These sublimits may be reallocated from time to time among the three borrowers within the $975.0 aggregate commitment. Spire may use its line to provide for the funding needs of various subsidiaries. Spire, Spire Missouri, and Spire Alabama expect to use the loan agreement for general corporate purposes, including short-term borrowings and letters of credit. The agreement also contains financial covenants limiting each borrower’s consolidated total debt, including short-term debt, to no more than 70% of its total capitalization. As defined in the line of credit, on September 30, 2017, total debt was 56% of total capitalization for the consolidated Company, 50% for Spire Missouri, and 33% for Spire Alabama. There were no borrowings against this credit facility as of September 30, 2017 . On December 21, 2016, Spire established a commercial paper program (Program) pursuant to which Spire may issue short-term, unsecured commercial paper notes (Notes). Amounts available under the Program may be borrowed, repaid, and re-borrowed from time to time, with the aggregate face or principal amount of the Notes outstanding under the Program at any time not to exceed $975.0 . The Notes may have maturities of up to 365 days from date of issue. The net proceeds of the issuances of the Notes are expected to be used for general corporate purposes, including to provide working capital for both utility and non-utility subsidiaries. As of September 30, 2017, Notes outstanding under the Program totaled $477.3 . Information about Spire’s consolidated short-term borrowings is presented below. Based on average short-term borrowings for the year ended September 30, 2017 , an increase in the average interest rate of 100 basis points would decrease Spire’s pre-tax earnings and cash flows by approximately $4.9 on an annual basis, portions of which may be offset through the application of PGA or GSA carrying costs. Spire Short ‑ term Borrowings 1 Spire Missouri Commercial Paper Borrowings 2 Spire Alabama Total Short ‑t erm Borrowings Year Ended September 30, 2017 Weighted average borrowings outstanding $369.0 $88.5 $28.3 $485.8 Weighted average interest rate 1.3% 0.9% 1.6% 1.2% Range of borrowings outstanding $73.0 - $675.6 $0.0 - $329.7 $0.0 - $102.5 $395.5 - $675.6 As of September 30, 2017 Borrowings outstanding $477.3 $— $— $477.3 Weighted average interest rate 1.5% —% —% 1.5% Year Ended September 30, 2016 Weighted average borrowings outstanding $42.7 $201.0 $30.2 $273.9 Weighted average interest rate 1.6% 0.7% 1.4% 0.9% Range of borrowings outstanding $0.0 - $82.0 $43.0 - $307.2 $0.0 - $82.0 $73.1 - $427.2 As of September 30, 2016 Borrowings outstanding $73.0 $243.7 $82.0 $398.7 Weighted average interest rate 1.8% 0.8% 1.5% 1.1% 1 Spire Short-term Borrowings includes bank line borrowings of Spire Inc. (excluding its subsidiaries) and, since January 1, 2017, commercial paper. Of Spire’s $477.3 borrowings outstanding as of September 30, 2017, $440.0 was used to provide funding to its subsidiaries, including Spire Missouri ( $203.0 ), Spire Alabama ( $169.9 ), Spire EnergySouth and subsidiaries ( $12.9 ), Spire STL Pipeline LLC ( $26.6 ), and others ( $27.6 ). 2 The commercial paper program for Spire Missouri terminated February 2, 2017. Spire Missouri Information about Spire Missouri’s short-term borrowings is presented below. Based on average short-term borrowings for the year ended September 30, 2017, an increase in the average interest rate of 100 basis points would decrease Spire Missouri’s pre-tax earnings and cash flows by approximately $2.8 on an annual basis, portions of which may be offset through the application of PGA carrying costs. Commercial Paper Borrowings Borrowings from Spire Total Short-term Borrowings Year Ended September 30, 2017 Weighted average borrowings outstanding $88.5 $195.5 $284.0 Weighted average interest rate 0.9% 1.3% 1.2% Range of borrowings outstanding $0.0 - $329.7 $0.0 - $338.6 $168.3 - $358.9 As of September 30, 2017 Borrowings outstanding $— $203.0 $203.0 Weighted average interest rate —% 1.5% 1.5% Year Ended September 30, 2016 Weighted average borrowings outstanding $201.0 $14.7 $215.7 Weighted average interest rate 0.7% 0.8% 0.7% Range of borrowings outstanding $43.0 - $307.2 $0.0 - $114.2 $127.8 - $ 307.2 As of September 30, 2016 Borrowings outstanding $243.7 $— $243.7 Weighted average interest rate 0.8% —% 0.8% Spire Alabama Information about Spire Alabama’s short-term borrowings is presented below. Based on average short-term borrowings for the year ended September 30, 2017, an increase in the average interest rate of 100 basis points would decrease Spire Alabama’s pre-tax earnings and cash flows by approximately $1.1 on an annual basis, portions of which may be offset through the application of GSA carrying costs. Bank Line Borrowings Borrowings from Spire Total Short-term Borrowings Year Ended September 30, 2017 Weighted average borrowings outstanding $28.3 $78.6 $106.9 Weighted average interest rate 1.6% 1.4% 1.5% Range of borrowings outstanding $0.0 - $102.5 $0.0 - $171.0 $74.0 - $171.0 As of September 30, 2017 Borrowings outstanding $— $169.9 $169.9 Weighted average interest rate —% 1.5% 1.5% Year Ended September 30, 2016 Weighted average borrowings outstanding $30.2 $12.4 $42.6 Weighted average interest rate 1.4% 1.4% 1.4% Range of borrowings outstanding $0.0 - $82.0 $0.0 - $61.9 $19.0 - $82.0 As of September 30, 2016 Borrowings outstanding $82.0 $— $82.0 Weighted average interest rate 1.5% —% 1.5%

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
FAIR VALUE OF FINANCIAL INSTRUMENTS	Sep. 30, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS Spire The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for the Company are as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) As of September 30, 2017 Cash and cash equivalents $ 7.4 $ 7.4 $ 7.4 $ — Short-term debt 477.3 477.3 — 477.3 Long-term debt, including current portion 2,095.0 2,210.3 — 2,210.3 As of September 30, 2016 Cash and cash equivalents $ 5.2 $ 5.2 $ 5.2 $ — Short-term debt 398.7 398.7 — 398.7 Long-term debt, including current portion 2,070.7 2,257.1 — 2,257.1 Spire Missouri The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for Spire Missouri are as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) As of September 30, 2017 Cash and cash equivalents $ 2.5 $ 2.5 $ 2.5 $ — Short-term debt 203.0 203.0 — 203.0 Long-term debt, including current portion 973.9 1,056.9 — 1,056.9 As of September 30, 2016 Cash and cash equivalents $ 2.1 $ 2.1 $ 2.1 $ — Short-term debt 243.7 243.7 — 243.7 Long-term debt 804.1 900.4 — 900.4 Spire Alabama The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for Spire Alabama are as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) As of September 30, 2017 Cash and cash equivalents $ 0.1 $ 0.1 $ 0.1 $ — Short-term debt 169.9 169.9 — 169.9 Long-term debt 247.8 269.4 — 269.4 As of September 30, 2016 Short-term debt $ 82.0 $ 82.0 $ — $ 82.0 Long-term debt, including current portion 247.6 275.5 — 275.5 The carrying amounts for cash and cash equivalents and short-term debt approximate fair value due to the short maturity of these instruments. The fair values of long-term debt are estimated based on market prices for similar issues. Refer to Note 9 , Fair Value Measurements, for information on financial instruments measured at fair value on a recurring basis.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
FAIR VALUE MEASUREMENTS	Sep. 30, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Spire The information presented below categorizes the assets and liabilities in the balance sheets that are accounted for at fair value on a recurring basis in periods subsequent to initial recognition. The mutual funds included in Level 1 are valued based on exchange-quoted market prices of individual securities. The mutual funds included in Level 2 are valued based on the closing net asset value per unit. Derivative instruments included in Level 1 are valued using quoted market prices on the NYMEX. Derivative instruments classified as Level 2 include physical commodity derivatives that are valued using Over-the-Counter Bulletin Board (OTCBB), broker, or dealer quotation services whose prices are derived principally from, or are corroborated by, observable market inputs. Also included in Level 2 are certain derivative instruments that have values that are similar to, and correlate with, quoted prices for exchange-traded instruments in active markets. Derivative instruments included in Level 3 are valued using generally unobservable inputs that are based upon the best information available and reflect management’s assumptions about how market participants would price the asset or liability. There were no material Level 3 balances as of September 30, 2017 or 2016 . The Company’s and the Utilities’ policy is to recognize transfers between the levels of the fair value hierarchy, if any, as of the beginning of the interim reporting period in which circumstances change or events occur to cause the transfer. The mutual funds are included in “Other investments” on the Company’s balance sheets and in “Property and other investments” on Spire Missouri’s balance sheets. Derivative assets and liabilities, including receivables and payables associated with cash margin requirements, are presented net on the balance sheets when a legally enforceable netting agreement exist between the Company or Spire Missouri and the counterparty to the derivative contract. For additional information on derivative instruments, see Note 10 , Derivative Instruments and Hedging Activities. Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of September 30, 2017 ASSETS Gas Utility: US stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — Gasoline and heating oil contracts 0.1 — — — 0.1 Gas Marketing: NYMEX/ICE natural gas contracts 1.3 1.3 — (2.1 ) 0.5 Natural gas commodity contracts — 6.8 0.1 (1.2 ) 5.7 Total $ 23.1 $ 12.2 $ 0.1 $ (6.7 ) $ 28.7 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 1.8 0.3 — (2.1 ) — Natural gas commodity contracts — 8.4 — (1.2 ) 7.2 Other: Interest rate swaps — 0.9 — — 0.9 Total $ 3.7 $ 9.6 $ — $ (5.2 ) $ 8.1 As of September 30, 2016 ASSETS Gas Utility: US stock/bond mutual funds $ 16.8 $ 4.1 $ — $ — $ 20.9 NYMEX/ICE natural gas contracts 5.3 — — (0.4 ) 4.9 Gasoline and heating oil contracts 0.4 — — (0.3 ) 0.1 Gas Marketing: NYMEX/ICE natural gas contracts 0.4 3.4 — (3.4 ) 0.4 Natural gas commodity contracts — 8.7 0.2 (0.9 ) 8.0 Total $ 22.9 $ 16.2 $ 0.2 $ (5.0 ) $ 34.3 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.6 $ — $ — $ (1.6 ) $ — OTCBB natural gas contracts — 0.2 — — 0.2 Gas Marketing: NYMEX/ICE natural gas contracts 3.5 1.6 — (5.1 ) — Natural gas commodity contracts — 2.6 — (0.9 ) 1.7 Other: Interest rate swaps — 3.0 — — 3.0 Total $ 5.1 $ 7.4 $ — $ (7.6 ) $ 4.9 Spire Missouri Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of September 30, 2017 ASSETS US stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — Gasoline and heating oil contracts 0.1 — — — 0.1 Total $ 21.8 $ 4.1 $ — $ (3.4 ) $ 22.5 LIABILITIES NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — Total $ 1.9 $ — $ — $ (1.9 ) $ — As of September 30, 2016 ASSETS US stock/bond mutual funds $ 16.8 $ 4.1 $ — $ — $ 20.9 NYMEX/ICE natural gas contracts 5.3 — — (0.4 ) 4.9 Gasoline and heating oil contracts 0.3 — — (0.3 ) — Total $ 22.4 $ 4.1 $ — $ (0.7 ) $ 25.8 LIABILITIES NYMEX/ICE natural gas contracts $ 1.6 $ — $ — $ (1.6 ) $ — OTCBB natural gas contracts — 0.2 — — 0.2 Total $ 1.6 $ 0.2 $ — $ (1.6 ) $ 0.2 Spire Alabama During the fiscal second quarter of 2016 Spire Alabama commenced a gasoline derivative program to stabilize the cost of fuel used in operations. As of September 30, 2017, the fair value of related gasoline contracts was not significant.

DERIVATIVE INSTRUMENTS AND HEDG

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	12 Months Ended
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES Spire Spire Missouri has a risk management policy to utilize various derivatives, including futures contracts, exchange-traded options, and swaps for the explicit purpose of managing price risk associated with purchasing and delivering natural gas on a regular basis to customers in accordance with its tariffs. The objective of this policy is to limit Spire Missouri’s exposure to natural gas price volatility and to manage, hedge and mitigate substantial price risk. Further discussion of this policy can be found in the Spire Missouri section. From time to time Spire Missouri and Spire Alabama purchase NYMEX futures and options contracts to help stabilize operating costs associated with forecasted purchases of gasoline and diesel fuels used to power vehicles and equipment used in the course of their business. Further information on these derivatives can be found in the Spire Missouri and Spire Alabama sections, respectively. In the course of its business, Spire’s gas marketing subsidiary, Spire Marketing, which includes its wholly owned subsidiary Spire Storage Inc., enters into commitments associated with the purchase or sale of natural gas. Certain of Spire Marketing’s derivative natural gas contracts are designated as normal purchases or normal sales and, as such, are excluded from the scope of ASC Topic 815 and are accounted for as executory contracts on an accrual basis. Any of Spire Marketing’s derivative natural gas contracts that are not designated as normal purchases or normal sales are accounted for at fair value. At September 30, 2017 , the fair values of 202.1 million MMBtu of non-exchange traded natural gas commodity contracts were reflected in the Consolidated Balance Sheet. Of these contracts, 156.8 million MMBtu will settle during fiscal 2018 , and 34.3 million MMBtu, 5.9 million MMBtu, 4.1 million MMBtu, 0.9 million MMBtu, and 0.1 million MMBtu will settle during fiscal years 2019 , 2020 , 2021 , 2022, and 2023, respectively. These contracts have not been designated as hedges; therefore, changes in the fair value of these contracts are reported in earnings each period. Furthermore, Spire Marketing manages the price risk associated with its fixed-priced commitments by either closely matching the offsetting physical purchase or sale of natural gas at fixed prices or through the use of NYMEX or ICE futures, swap, and option contracts to lock in margins. At September 30, 2017 , Spire Marketing’s unmatched fixed-price positions were not material to Spire’s financial position or results of operations. Spire Marketing’s NYMEX and ICE natural gas futures, swap, and option contracts used to lock in margins may be designated as cash flow hedges of forecasted transactions for financial reporting purposes. During fiscal 2015, Spire Alabama entered into interest rate swap transactions to protect itself against adverse movement in interest rates in anticipation of its issuance of $115.0 of long-term debt. The notional amount of these interest rate swaps was $104.5 . These derivative instruments were designated as cash flow hedges of forecasted transactions. These forward starting swaps involved the payment of a fixed interest rate and the receipt of the London Interbank Offered Rate (LIBOR) over the terms specified in the contracts. Termination of these interest rate swap agreements later in fiscal 2015 resulted in a $2.7 gain which was recorded as a regulatory liability. Of the total issuance of long-term debt, $35.0 was issued on September 15, 2015 and $80.0 was issued on December 1, 2015, and the gain is being amortized to reduce interest expense over the hedged periods. During fiscal 2016, Spire entered into interest rate swap agreements, with a notional amount of $85.0 , to effectively lock in interest rates on a portion of the long-term debt it anticipated issuing to finance its acquisition of Spire EnergySouth. These derivative instruments were designated as cash flow hedges of forecasted transactions. Termination of the interest rate swap agreements later in fiscal 2016 resulted in a $0.4 loss recorded in accumulated other comprehensive loss to be amortized to interest expense over the life of the related debt issuances. Also during fiscal 2016, Spire entered into interest rate swap transactions with a notional amount of $225.0 to protect itself against adverse movement in interest rates in anticipation of the issuance of long-term debt in fiscal 2017. These hedge positions were settled during fiscal 2017, resulting in a gain of $14.1 which will be amortized to reduce interest expense over the hedged periods. Also during fiscal 2017, Spire entered into a ten-year interest rate swap with a fixed interest rate of 2.658 % and a notional amount of $60.0 to protect itself against adverse movements in interest rates on future interest rate payments. The Company recorded a $0.9 mark-to-market loss on these swaps as part of other comprehensive income for the year ended September 30, 2017. The Company’s and Spire Missouri’s exchange-traded/cleared derivative instruments consist primarily of NYMEX and ICE positions. The NYMEX is the primary national commodities exchange on which natural gas derivatives are traded. Open NYMEX/ICE natural gas futures and swap positions at September 30, 2017 were as follows: Gas Utility Gas Marketing MMBtu (millions) Avg. Price Per MMBtu MMBtu (millions) Avg. Price Per MMBtu NYMEX/ICE open short futures positions/swap positions Fiscal 2018 — $ — 8.66 $ 3.34 Fiscal 2019 — — 2.07 3.13 NYMEX/ICE open long futures/swap positions Fiscal 2018 14.18 2.98 3.78 3.16 Fiscal 2019 1.68 2.89 1.84 3.02 Fiscal 2020 — — 0.66 2.91 Fiscal 2021 — — 0.28 2.90 Fiscal 2022 — — 0.22 3.00 ICE open short daily swap positions Fiscal 2018 — — 1.32 2.87 ICE open long daily swap positions Fiscal 2018 — — 0.78 2.79 ICE open short basis swap positions Fiscal 2018 — — 14.04 0.10 Fiscal 2019 — — 3.35 0.27 Fiscal 2020 — — 0.31 0.36 ICE open long basis swap positions Fiscal 2018 — — 11.12 0.38 Fiscal 2019 — — 4.51 0.45 Fiscal 2020 — — 0.62 0.45 At September 30, 2017 , Spire Missouri also had 33.9 million MMBtu of other price mitigation in place through the use of NYMEX natural gas option-based strategies while Spire Marketing had none. Derivative instruments designated as cash flow hedges of forecasted transactions are recognized on the balance sheets of the Company at fair value, and the change in fair value of the effective portion of these hedge instruments is recorded, net of income tax, in other comprehensive income or loss (OCI). Accumulated other comprehensive income or loss (AOCI) is a component of Total Common Stock Equity. Amounts are reclassified from AOCI into earnings when the hedged items affect net income, using the same revenue or expense category that the hedged item impacts. Based on market prices at September 30, 2017 , it is expected that an immaterial amount of unrealized gains will be reclassified into the Consolidated Statements of Income of the Company during the next twelve months. Cash flows from hedging transactions are classified in the same category as the cash flows from the items that are being hedged in the Consolidated Statements of Cash Flows. Effect of Derivative Instruments on the Consolidated Statements of Income and Consolidated Statements of Comprehensive Income Location of Gain (Loss) Recorded in Income 2017 2016 2015 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gas Marketing natural gas contracts $ — $ (0.6 ) $ (4.3 ) Gas Utility gasoline and heating oil contracts 0.1 — (1.2 ) Interest rate swaps 11.4 (3.4 ) — Total $ 11.5 $ (4.0 ) $ (5.5 ) Effective portion of gain (loss) reclassified from AOCI to income: Natural gas contracts Gas Marketing Operating Revenues $ (0.4 ) $ 4.3 $ 1.7 Gas Marketing Operating Expenses 0.1 (4.9 ) (5.2 ) Subtotal (0.3 ) (0.6 ) (3.5 ) Gasoline and heating oil contracts Gas Utility Other Operating Expenses 0.2 (0.5 ) (0.9 ) Interest rate swaps Interest Expense 0.1 — — Total $ — $ (1.1 ) $ (4.4 ) Ineffective portion of gain (loss) on derivatives recognized in income: Natural gas contracts Gas Marketing Operating Revenues $ — $ 0.1 $ — Gas Marketing Operating Expenses — 0.1 (0.5 ) Subtotal — 0.2 (0.5 ) Gasoline and heating oil contracts Gas Utility Other Operating Expenses — 0.1 0.1 Interest rate swaps Interest Expense 0.5 — — Total $ 0.5 $ 0.3 $ (0.4 ) Derivatives Not Designated as Hedging Instruments* Gain (loss) recognized in income on derivatives: Natural gas commodity contracts Gas Marketing Operating Revenues $ 0.7 $ 12.3 $ (1.3 ) NYMEX / ICE natural gas contracts Gas Marketing Operating Revenues (4.4 ) (1.7 ) (9.6 ) Gasoline and heating oil contracts Other Income and (Income Deductions) - Net — — (0.2 ) Total $ (3.7 ) $ 10.6 $ (11.1 ) * Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not designated as hedging instruments for financial reporting purposes, are deferred pursuant to the Missouri Utilities’ PGA clauses and initially recorded as regulatory assets or regulatory liabilities. These gains and losses are excluded from the table above because they have no direct impact on the statements of income. Such amounts are recognized in the statements of income as a component of Regulated Gas Distribution Natural and Propane Gas operating expenses when they are recovered through the PGA clause and reflected in customer billings. Fair Value of Derivative Instruments in the Consolidated Balance Sheets Asset Derivatives* Liability Derivatives* September 30, 2017 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Gas Utility: Gasoline and heating oil contracts Derivative Instrument Assets $ 0.1 Derivative Instrument Assets $ — Gas Marketing: Natural gas contracts Derivative Instrument Assets 0.3 Derivative Instrument Assets 0.2 Deferred Charges – Other 0.3 Deferred Charges – Other — Other: Interest rate swaps Current Liabilities - Other — Current Liabilities - Other 0.9 Subtotal 0.7 1.1 Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Accounts Receivable – Other 3.4 Accounts Receivable – Other 1.9 Gas Marketing: NYMEX / ICE natural gas contracts Derivative Instrument Assets 1.7 Derivative Instrument Assets 1.4 Deferred Charges – Other 0.3 Deferred Charges – Other 0.5 Natural gas commodity Derivative Instrument Assets 5.3 Derivative Instrument Assets 0.1 Other Deferred Charges 0.4 Other Deferred Charges — Current Liabilities – Other 0.8 Current Liabilities – Other 5.0 Deferred Credits – Other 0.4 Deferred Credits – Other 3.3 Subtotal 12.3 12.2 Total derivatives $ 13.0 $ 13.3 September 30, 2016 Derivatives designated as hedging instruments Gas Utility: Gasoline and heating oil contracts Derivative Instrument Assets $ 0.3 Derivative Instrument Assets $ — Gas Marketing: Natural gas contracts Derivative Instrument Assets 2.5 Derivative Instrument Assets 0.8 Deferred Charges - Other 0.4 Deferred Charges - Other 0.1 Other: Interest rate swaps Derivative Instrument Assets — Derivative Instrument Assets 3.0 Subtotal 3.2 3.9 Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Accounts Receivable – Other 5.4 Accounts Receivable – Other 1.6 Derivative Instrument Assets — Derivative Instrument Assets 0.2 Gas Marketing: NYMEX / ICE natural gas contracts Derivative Instrument Assets 0.8 Derivative Instrument Assets 4.1 Deferred Charges – Other — Deferred Charges – Other 0.1 Natural gas commodity Derivative Instrument Assets 6.5 Derivative Instrument Assets 0.2 Other Deferred Charges 2.1 Other Deferred Charges 0.3 Current Liabilities – Other 0.2 Current Liabilities – Other 2.0 Deferred Credits – Other 0.2 Deferred Credits – Other 0.1 Subtotal 15.2 8.6 Total derivatives $ 18.4 $ 12.5 * The fair values of Asset Derivatives and Liability Derivatives exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the balance sheets. As such, the gross balances presented in the table above are not indicative of the Company’s net economic exposure. Refer to Note 9 , Fair Value Measurements, for information on the valuation of derivative instruments. Following is a reconciliation of the amounts in the tables above to the amounts presented in the Consolidated Balance Sheets: 2017 2016 Fair value of asset derivatives presented above $ 13.0 $ 18.4 Fair value of cash margin (payable) receivable offset with derivatives (1.5 ) 2.5 Netting of assets and liabilities with the same counterparty (5.3 ) (7.6 ) Total $ 6.2 $ 13.3 Derivative Instrument Assets, per Consolidated Balance Sheets: Derivative instrument assets $ 5.9 $ 11.4 Deferred Charges – Other 0.3 1.9 Total $ 6.2 $ 13.3 Fair value of liability derivatives presented above $ 13.3 $ 12.5 Netting of assets and liabilities with the same counterparty (5.3 ) (7.6 ) Total $ 8.0 $ 4.9 Derivative Instrument Liabilities, per Consolidated Balance Sheets: Current Liabilities – Other $ 4.9 $ 4.8 Deferred Credits – Other 3.1 0.1 Total $ 8.0 $ 4.9 Additionally, at September 30, 2017 and 2016 , the Company had $4.0 and $2.9 , respectively, in cash margin receivables not offset with derivatives, which are presented in Accounts Receivable – Other. Spire Missouri Spire Missouri has a risk management policy to utilize various derivatives, including futures contracts, exchange-traded options, swaps and over-the-counter instruments for the explicit purpose of managing price risk associated with purchasing and delivering natural gas on a regular basis to customers in accordance with its tariffs. The objective of this policy is to limit Spire Missouri’s exposure to natural gas price volatility and to manage, hedge and mitigate substantial price risk. This policy strictly prohibits speculation and permits Spire Missouri to hedge current physical natural gas purchase commitments or forecasted or anticipated future peak (maximum) physical need for natural gas delivered. Costs and cost reductions, including carrying costs, associated with Spire Missouri’s use of natural gas derivative instruments are allowed to be passed on to Spire Missouri customers through the operation of its PGA clause, through which the MoPSC allows Spire Missouri to recover gas supply costs, subject to prudence review by the MoPSC. Accordingly, Spire Missouri does not expect any adverse earnings impact as a result of the use of these derivative instruments. Spire Missouri does not designate these instruments as hedging instruments for financial reporting purposes because gains or losses associated with the use of these derivative instruments are deferred and recorded as regulatory assets or regulatory liabilities pursuant to ASC Topic 980, “Regulated Operations,” and, as a result, have no direct impact on the statements of income. The timing of the operation of the PGA clause may cause interim variations in short-term cash flows, because Spire Missouri is subject to cash margin requirements associated with changes in the values of these instruments. Nevertheless, carrying costs associated with such requirements are recovered through the PGA clause. From time to time, Spire Missouri purchases NYMEX futures and options contracts to help stabilize operating costs associated with forecasted purchases of gasoline and diesel fuels used to power vehicles and equipment used in the course of its business. At September 30, 2017 , Spire Missouri held 0.3 million gallons of gasoline futures contracts at an average price of $1.27 per gallon. Most of these contracts, the longest of which extends to December 2017, are designated as cash flow hedges of forecasted transactions pursuant to ASC Topic 815, “Derivatives and Hedging.” The gains or losses on these derivative instruments are not subject to Spire Missouri’s PGA clause. Derivative instruments designated as cash flow hedges of forecasted transactions are recognized on the balance sheets at fair value and the change in the fair value of the effective portion of these hedge instruments is recorded, net of income tax, in OCI. AOCI is a component of Total Common Stock Equity. Amounts are reclassified from AOCI into earnings when the hedged items affect net income, using the same revenue or expense category that the hedged item impacts. Based on market prices at September 30, 2017 , it is expected that an immaterial amount of pre-tax gains will be reclassified into the statements of income during fiscal 2018 . Cash flows from hedging transactions are classified in the same category as the cash flows from the items that are being hedged in the statements of cash flows. Spire Missouri’s derivative instruments consist primarily of NYMEX positions. The NYMEX is the primary national commodities exchange on which natural gas derivatives are traded. Open NYMEX natural gas futures positions at September 30, 2017 were as follows: MMBtu (millions) Avg. Price Per MMBtu NYMEX/ICE open long futures/swap positions Fiscal 2018 14.18 $ 2.98 Fiscal 2019 1.68 2.89 At September 30, 2017 , Spire Missouri also had 33.9 million MMBtu of other price mitigation in place through the use of NYMEX natural gas option-based strategies. Effect of Derivative Instruments on the Statements of Income and Statements of Comprehensive Income Location of Gain (Loss) Recorded in Income 2017 2016 2015 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gasoline and heating oil contracts $ 0.1 $ — $ (1.2 ) Effective portion of gain (loss) reclassified from AOCI to income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ 0.2 $ (0.5 ) $ (0.9 ) Ineffective portion of gain (loss) on derivatives recognized in income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ — $ 0.1 $ 0.1 Derivatives Not Designated as Hedging Instruments* Gain (loss) recognized in income on derivatives: Gasoline and heating oil contracts Other Income and (Income Deductions) - Net $ — $ — $ (0.2 ) * Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not designated as hedging instruments for financial reporting purposes, are deferred pursuant to the Spire Missouri’s PGA clauses and initially recorded as regulatory assets or regulatory liabilities. These gains and losses are excluded from the table above because they have no direct impact on the Statements of Income. Such amounts are recognized in the Statements of Income as a component of Regulated Gas Distribution Natural and Propane Gas operating expenses when they are recovered through the PGA clause and reflected in customer billings. Fair Value of Derivative Instruments in the Balance Sheets Asset Derivatives* Liability Derivatives* September 30, 2017 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Gasoline and heating oil contracts Derivative Instrument Assets $ 0.1 Derivative Instrument Assets $ — Derivatives not designated as hedging instruments Natural gas contracts Accounts Receivable – Other 3.4 Accounts Receivable – Other 1.9 Total derivatives $ 3.5 $ 1.9 September 30, 2016 Derivatives designated as hedging instruments Gasoline and heating oil contracts Derivative Instrument Assets $ 0.3 Derivative Instrument Assets $ — Subtotal 0.3 — Derivatives not designated as hedging instruments Natural gas contracts Accounts Receivable – Other 5.4 Accounts Receivable – Other 1.6 OTCBB natural gas contracts Derivative Instrument Assets — Derivative Instrument Assets 0.2 Subtotal 5.4 1.8 Total derivatives $ 5.7 $ 1.8 * The fair values of Asset Derivatives and Liability Derivatives exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the Balance Sheets. As such, the gross balances presented in the table above are not indicative of Spire Missouri’s net economic exposure. Refer to Note 9 , Fair Value Measurements, for information on the valuation of derivative instruments. Following is a reconciliation of the amounts in the tables above to the amounts presented in Spire Missouri’s Balance Sheets: 2017 2016 Fair value of asset derivatives presented above $ 3.5 $ 5.7 Fair value of cash margin (payable) receivable offset with derivatives (1.5 ) 0.8 Netting of assets and liabilities with the same counterparty (1.9 ) (1.6 ) Total $ 0.1 $ 4.9 Derivative Instrument Assets, per Balance Sheets: Derivative instrument assets $ 0.1 $ 4.9 Total $ 0.1 $ 4.9 Fair value of liability derivatives presented above $ 1.9 $ 1.8 Netting of assets and liabilities with the same counterparty (1.9 ) (1.6 ) Total $ — $ 0.2 Derivative Instrument Liabilities, per Balance Sheets: Current Liabilities – Other $ — $ 0.2 Total $ — $ 0.2 Additionally, at September 30, 2017 and 2016, Spire Missouri had $4.0 and $0.5 , respectively, in cash margin receivables not offset with derivatives, which are presented in Accounts Receivable – Other. Spire Alabama In prior years, Spire Alabama entered into cash flow derivative commodity instruments to hedge its exposure to price fluctuations on its gas supply. Spire Alabama recognizes all derivatives at fair value as either assets or liabilities on the balance sheet. Any realized gains or losses are passed through to customers using the mechanisms of the GSA rider in accordance with Spire Alabama’s APSC approved tariff. During the second quarter of fiscal 2015, Spire Alabama entered into certain interest rate swap transactions to protect itself against adverse movement in interest rates in anticipation of its issuance of $115.0 of long-term debt. Spire Alabama received prior approval from the APSC to enter into these hedges. The notional amount of interest rate swaps outstanding was $80.5 with stated maturities ranging from 2025 to 2045 and fixed interest rates ranging between 2.18% and 2.85% . In April 2015, Spire Alabama entered into an additional hedge with a notional amount of $24.0 and terms within the same range. These derivative instruments were designated as cash flow hedges of forecasted transactions. These forward starting swaps involved the payment of a fixed interest rate and the receipt of LIBOR over the terms specified in the contracts. On May 21, 2015, the interest rate swap agreements were terminated and the settlement resulted in a $2.7 gain which was recorded as a regulatory liability. Of the total issuance of long-term debt, $35.0 was issued on September 15, 2015 and the remaining $80.0 was issued on December 1, 2015. During the fiscal second quarter of 2016, Spire Alabama commenced a gasoline derivative program to help stabilize operating costs associated with forecasted purchases of gasoline and diesel fuels used to power vehicles and equipment used in the course of its business. At September 30, 2017 , Spire Alabama held 0.1 million gallons of gasoline futures contracts at an average price of $1.28 per gallon. Most of these contracts, the longest of which extends to December 2017, are designated as cash flow hedges of forecasted transactions pursuant to ASC Topic 815, “Derivatives and Hedging.” The gains or losses on these derivative instruments are not subject to Spire Alabama’s GSA rider. As of September 30, 2017 and 2016, the fair value of gasoline contracts was not significant.

CONCENTRATIONS OF CREDIT RISK

CONCENTRATIONS OF CREDIT RISK	12 Months Ended
CONCENTRATIONS OF CREDIT RISK	Sep. 30, 2017
Risks and Uncertainties [Abstract]
CONCENTRATIONS OF CREDIT RISK	CONCENTRATIONS OF CREDIT RISK Other than in Spire Marketing, Spire has no significant concentration of credit risk. A significant portion of Spire Marketing’s transactions are with (or are associated with) energy producers, utility companies, and pipelines. The concentration of transactions with these counterparties has the potential to affect the Company’s overall exposure to credit risk, either positively or negatively, in that each of these three groups may be affected similarly by changes in economic, industry, or other conditions. To manage this risk, as well as credit risk from significant counterparties in these and other industries, Spire Marketing has established procedures to determine the creditworthiness of its counterparties. These procedures include obtaining credit ratings and credit reports, analyzing counterparty financial statements to assess financial condition, and considering the industry environment in which the counterparty operates. This information is monitored on an ongoing basis. In some instances, Spire Marketing may require credit assurances such as prepayments, letters of credit, or parental guarantees. In addition, Spire Marketing may enter into netting arrangements to mitigate credit risk with counterparties in the energy industry with whom it conducts both sales and purchases of natural gas. Sales are typically made on an unsecured credit basis with payment due the month following delivery. Accounts receivable amounts are closely monitored and provisions for uncollectible amounts are accrued when losses are probable. Spire Marketing records accounts receivable, accounts payable, and prepayments for physical sales and purchases of natural gas on a gross basis. The amount included in accounts receivable attributable to energy producers and their marketing affiliates amounted to $17.9 at September 30, 2017 ( $8.9 reflecting netting arrangements). Spire Marketing’s accounts receivable attributable to utility companies and their marketing affiliates comprised $58.2 of total accounts receivable at September 30, 2017 ( $55.8 reflecting netting arrangements). Spire Marketing also has concentrations of credit risk with certain individually significant counterparties and with pipeline companies associated with its natural gas receivable amount. At September 30, 2017 , the amounts included in accounts receivable from Spire Marketing’s five largest counterparties (in terms of net accounts receivable exposure) totaled $23.8 ( $23.1 reflecting netting arrangements). Four of these five counterparties are investment-grade rated companies. The fifth is not rated, but each of its owners is investment-grade.

INCOME TAXES

INCOME TAXES	12 Months Ended
INCOME TAXES	Sep. 30, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Spire The Company’s provision for income taxes charged during the fiscal years ended September 30, 2017 , 2016 , and 2015 are as follows: 2017 2016 2015 Federal Current $ 0.1 $ 0.1 $ (3.3 ) Deferred 67.7 62.0 58.8 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current 0.5 0.6 — Deferred 9.5 7.0 6.9 Total income tax expense $ 77.6 $ 69.5 $ 62.2 The Company’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2017 2016 2015 Federal income tax statutory rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 2.8 2.8 3.0 Certain expenses capitalized on books and deducted on tax return (2.3 ) (3.4 ) (3.7 ) Taxes related to prior years (0.9 ) (0.2 ) (0.6 ) Other items – net * (2.2 ) (1.7 ) (2.5 ) Effective income tax rate 32.4 % 32.5 % 31.2 % * Other consists primarily of property adjustments. The Company’s significant items comprising the net deferred tax liability recorded in the Consolidated Balance Sheets as of September 30 are as follows: 2017 2016 Deferred tax assets: Reserves not currently deductible $ 31.5 $ 21.3 Pension and other postretirement benefits 58.6 68.3 Operating losses 169.6 102.3 Other 26.0 — Deferred tax assets 285.7 191.9 Less: valuation allowance 0.5 0.9 Total deferred tax assets 285.2 191.0 Deferred tax liabilities: Relating to property 728.3 623.1 Regulatory pension and other postretirement benefits 108.0 106.8 Deferred gas costs 30.6 20.0 Other 125.8 48.4 Total deferred tax liabilities 992.7 798.3 Net deferred tax liability $ 707.5 $ 607.3 Other consists primarily of Goodwill related liabilities. In assessing whether deferred tax assets are realizable, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Management considers all significant available positive and negative evidence, including the existence of losses in recent years, the timing of deferred tax liability reversals, projected future taxable income, taxable income in carryback years, and tax planning strategies to assess the need for a valuation allowance. Based upon this evidence, management believes it is more likely than not the Company will realize the benefits of these deferred tax assets, except for the contribution carryforward valuation allowance noted below. The Company has federal and state loss carryforwards of approximately $478.6 at September 30, 2017 . The Company also has contribution carryforwards of approximately $12.1 at September 30, 2017 . The loss carryforwards begin to expire in fiscal 2030 for certain state purposes and fiscal 2035 for federal and other states purposes. The contribution carryforwards begin to expire in fiscal 2018. The Company has a valuation allowance of $0.5 as a portion of the contribution carryforward will not be realized prior to its expiration. The Company also has various tax credit carryforwards of approximately $2.5 that begin to expire in 2020. The Company recognizes the tax benefit from a tax position only if it is at least more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company records potential interest and penalties related to its uncertain tax positions as interest expense and other income deductions, respectively. Unrecognized tax benefits are reported as a reduction of a deferred tax asset for an operating loss carryforward. The following table presents a reconciliation of the beginning and ending balances of the Company’s unrecognized tax benefits: 2017 2016 2015 Unrecognized tax benefits, beginning of year $ 10.0 $ 7.1 $ 4.6 Increases related to tax positions taken in current year 2.4 3.4 2.9 Reductions due to lapse of applicable statute of limitations (1.4 ) (0.5 ) (0.4 ) Unrecognized tax benefits, end of year $ 11.0 $ 10.0 $ 7.1 The amount of unrecognized tax benefits which, if recognized, would affect the Company’s effective tax rate were $5.1 and $3.3 as of September 30, 2017 and 2016 , respectively. It is reasonably possible that events will occur in the next 12 months that could increase or decrease the amount of the Company’s unrecognized tax benefits. The Company does not expect that any such change will be significant to the Consolidated Balance Sheets. As of September 30, 2017 and 2016 , interest accrued associated with the Company’s uncertain tax positions was de minimis, and no penalties were accrued as of September 30, 2017 . The Company is subject to US federal income tax as well as income tax in various state and local jurisdictions. The Company is no longer subject to examination for fiscal years prior to 2014. Regarding the Company’s recent Spire EnergySouth acquisition, tax returns for calendar years 2013 through 2015 remain open and subject to examination by the Internal Revenue Service and state taxing jurisdictions. These returns cover periods during which Spire EnergySouth was owned by Sempra Global. The impact of any adjustments made to these returns by the relevant taxing authorities would be addressed by the indemnification provisions of the stock purchase agreement with Sempra Global. Spire Missouri Spire Missouri’s provision for income taxes charged during the fiscal years ended September 30, 2017 , 2016 , and 2015 are as follows: 2017 2016 2015 Federal Current $ — $ — $ (2.1 ) Deferred 42.0 37.5 40.9 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current — 0.1 (0.1 ) Deferred 5.7 8.0 4.7 Total income tax expense $ 47.5 $ 45.4 $ 43.2 Spire Missouri’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2017 2016 2015 Federal income tax statutory rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 2.8 2.8 2.8 Certain expenses capitalized on books and deducted on tax return (3.5 ) (4.8 ) (4.9 ) Taxes related to prior years (1.4 ) (0.2 ) (0.8 ) Other items – net * (3.3 ) (2.8 ) (3.0 ) Effective income tax rate 29.6 % 30.0 % 29.1 % * Other consists primarily of property adjustments. Spire Missouri’s significant items comprising the net deferred tax liability reported in the Balance Sheets as of September 30 are as follows: 2017 2016 Deferred tax assets: Reserves not currently deductible $ 25.3 $ 14.9 Pension and other postretirement benefits 52.7 56.9 Operating losses 52.0 29.9 Deferred tax assets 130.0 101.7 Less: valuation allowance 0.5 0.9 Total deferred tax assets 129.5 100.8 Deferred tax liabilities: Relating to utility property 563.2 497.0 Regulatory pension and other postretirement benefits 108.0 106.8 Deferred gas costs 25.0 20.0 Other 57.1 33.9 Total deferred tax liabilities 753.3 657.7 Net deferred tax liability $ 623.8 $ 556.9 Spire files a consolidated federal return and various state income tax returns and allocates income taxes to Spire Missouri and its other subsidiaries as if each entity were a separate taxpayer. In assessing whether deferred tax assets are realizable, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Management considers all significant available positive and negative evidence, including the existence of losses in recent years, the timing of deferred tax liability reversals, projected future taxable income, taxable income in carryback years, and tax planning strategies to assess the need for a valuation allowance. Based upon this evidence, management believes it is more likely than not that Spire Missouri will realize the benefits of these deferred tax assets, except for the contribution carryforward valuation allowance noted below. Spire Missouri has federal and state loss carryforwards of approximately $166.0 , at September 30, 2017 , based on a separate company basis. For federal tax purposes, these loss carryforwards may be utilized against income from another member of the consolidated group. Spire Missouri also has contribution carryforwards of approximately $11.2 at September 30, 2017 . The loss carryforwards begin to expire in fiscal 2035 for federal and state purposes. The contribution carryforwards begin to expire in fiscal 2018. Spire Missouri has a valuation allowance of $0.5 as a portion of the contribution carryforward will not be realized prior to its expiration. Spire Missouri also has approximately $2.0 of various tax credit carryforwards with expiration dates which begin to expire in 2020. Spire Missouri recognizes the tax benefit from a tax position only if it is at least more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. Spire Missouri records potential interest and penalties related to its uncertain tax positions as interest expense and other income deductions, respectively. Unrecognized tax benefits are reported as a reduction of a deferred tax asset for an operating loss carryforward. The following table presents a reconciliation of the beginning and ending balances of Spire Missouri unrecognized tax benefits: 2017 2016 2015 Unrecognized tax benefits, beginning of year $ 9.7 $ 6.9 $ 4.2 Increases related to tax positions taken in current year 2.4 3.3 2.9 Reductions due to lapse of applicable statute of limitations (1.4 ) (0.5 ) (0.2 ) Unrecognized tax benefits, end of year $ 10.7 $ 9.7 $ 6.9 The amount of unrecognized tax benefits, which, if recognized, would affect Spire Missouri’s effective tax rate were $4.8 and $3.1 as of September 30, 2017 and 2016 , respectively. It is reasonably possible that events will occur in the next 12 months that could increase or decrease the amount of Spire Missouri’s unrecognized tax benefits. Spire Missouri does not expect that any such change will be significant to Spire Missouri’s Balance Sheets. As of September 30, 2017 and 2016 , interest accrued associated with Spire Missouri’s uncertain tax positions was de minimis, and no penalties were accrued. Spire Missouri is subject to US federal income tax as well as income tax in various state and local jurisdictions, and is no longer subject to examination for fiscal years prior to 2014. Spire Alabama Spire Alabama’s provision for income taxes charged during the fiscal years ended September 30, 2017 , 2016 , and 2015 , are as follows: 2017 2016 2015 Federal Current $ — $ (0.8 ) $ — Deferred 31.6 29.4 25.9 State and local Current — — 0.1 Deferred 4.2 3.8 3.3 Total income tax expense $ 35.8 $ 32.4 $ 29.3 Spire Alabama’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2017 2016 2015 Federal income tax statutory rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 2.8 2.8 2.8 Other items – net 0.3 0.1 0.1 Effective income tax rate 38.1 % 37.9 % 37.9 % Spire Alabama’s significant items comprising the net deferred tax asset reported in the Balance Sheets as of September 30 are as follows: 2017 2016 Deferred tax assets: Reserves not currently deductible $ 6.0 $ 6.3 Pension and other postretirement benefits 4.4 11.4 Goodwill 214.4 233.4 Operating losses 88.3 60.2 Total deferred tax assets 313.1 311.3 Deferred tax liabilities: Relating to utility property 119.3 87.6 Other 8.2 2.3 Total deferred tax liabilities 127.5 89.9 Net deferred tax asset $ 185.6 $ 221.4 Spire files a consolidated federal return and various state income tax returns and allocates income taxes to Spire Alabama and its other subsidiaries as if each entity were a separate taxpayer. In assessing whether deferred tax assets are realizable, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Management considers all significant available positive and negative evidence, including the existence of losses in recent years, the timing of deferred tax liability reversals, projected future taxable income, taxable income in carryback years, and tax planning strategies to assess the need for a valuation allowance. Based upon this evidence, management believes it is more likely than not that Spire Alabama will realize the benefits of these deferred tax assets. On a separate company basis, Spire Alabama has federal and state loss carryforwards of approximately $233.5 , at September 30, 2017 generated since the acquisition. The loss carryforwards begin to expire in fiscal 2030 for state purposes and fiscal 2035 for federal purposes. For federal tax purposes, these loss carryforwards may be utilized against income from another member of the consolidated group. Spire Alabama recognizes the tax benefit from a tax position only if it is at least more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. Spire Alabama records potential interest and penalties related to its uncertain tax positions as interest expense and other income deductions, respectively. Spire Alabama has reported no unrecognized tax benefits for fiscal years 2017, 2016, and 2015. Spire Alabama is subject to US federal income tax as well as income tax in various state and local jurisdictions. Spire Alabama’s tax returns for the periods after 2013 remain open and subject to examination by the Internal Revenue Service and state taxing jurisdictions. The returns covering 2014 include the period during which Spire Alabama was owned by Energen. The impact of any adjustments made to those returns by the relevant taxing authorities would be addressed by the indemnification provisions of the stock purchase agreement with Energen.

PENSION PLANS AND OTHER POSTRET

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS	12 Months Ended
PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS	Sep. 30, 2017
Defined Contribution Plan [Abstract]
PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS	PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS The Spire information in this note reflects all plans of the Company, including information for plans of Spire EnergySouth since September 12, 2016. The net pension and postretirement obligations were re-measured at that acquisition date as well as at the fiscal year end. Pension Plans The pension plans of Spire consist of plans for employees at the Missouri Utilities, plans covering the employees of Spire Alabama, and plans covering employees of the subsidiaries of Spire EnergySouth. The Missouri Utilities have non-contributory, defined benefit, trusteed forms of pension plans covering the majority of their employees. Plan assets consist primarily of corporate and US government obligations and a growth segment consisting of exposure to equity markets, commodities, real estate and inflation-indexed securities, achieved through derivative instruments. Spire Alabama has non-contributory, defined benefit, trusteed forms of pension plans covering the majority of its employees. Qualified plan assets are comprised of mutual and commingled funds consisting of US equities with varying strategies, global equities, alternative investments, and fixed income investments. The net periodic pension costs include the following components: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Service cost – benefits earned during the period $ 20.5 $ 15.3 $ 17.3 $ 12.7 $ 10.0 $ 11.5 $ 6.2 $ 5.3 $ 5.8 Interest cost on projected benefit obligation 27.9 28.0 29.5 19.5 21.7 23.3 6.1 6.3 6.2 Expected return on plan assets (38.5 ) (34.9 ) (37.4 ) (28.1 ) (26.7 ) (29.2 ) (7.2 ) (8.2 ) (8.2 ) Amortization of prior service cost 1.0 0.4 0.5 1.0 0.4 0.5 — — — Amortization of actuarial loss 12.5 8.0 7.5 10.7 7.9 7.5 1.8 0.1 — Loss on lump-sum settlements and curtailments 17.9 3.3 19.6 13.5 — 18.0 4.6 3.3 1.6 Special termination benefits 0.9 1.6 — — 1.6 — — — — Subtotal 42.2 21.7 37.0 29.3 14.9 31.6 11.5 6.8 5.4 Regulatory adjustment (2.4 ) 17.8 (2.1 ) (4.1 ) 11.7 (5.2 ) 1.8 6.1 3.1 Net pension cost $ 39.8 $ 39.5 $ 34.9 $ 25.2 $ 26.6 $ 26.4 $ 13.3 $ 12.9 $ 8.5 Other changes in plan assets and pension benefit obligations recognized in other comprehensive income or loss include the following: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Current year actuarial loss $ 14.1 $ 46.8 $ 48.3 $ 14.8 $ 21.6 $ 26.0 $ 3.3 $ 25.2 $ 22.3 Amortization of actuarial loss (12.5 ) (8.0 ) (7.5 ) (10.7 ) (7.9 ) (7.5 ) (1.8 ) (0.1 ) — Acceleration of loss recognized due to settlement (18.2 ) (3.3 ) (19.6 ) (13.5 ) — (18.0 ) (4.5 ) (3.3 ) (1.6 ) Current year service cost — 5.0 — — 5.0 — — — — Current year prior year service cost (20.7 ) — — — — — (20.7 ) — — Amortization of prior service cost (1.0 ) (0.4 ) (0.5 ) (1.0 ) (0.4 ) (0.5 ) — — — Subtotal (38.3 ) 40.1 20.7 (10.4 ) 18.3 — (23.7 ) 21.8 20.7 Regulatory adjustment 38.0 (39.8 ) (21.2 ) 10.1 (18.0 ) (0.5 ) 23.7 (21.8 ) (20.7 ) Total recognized in OCI $ (0.3 ) $ 0.3 $ (0.5 ) $ (0.3 ) $ 0.3 $ (0.5 ) $ — $ — $ — Spire pension obligations are driven by separate plan and regulatory provisions governing Spire Missouri, Spire Alabama and Spire EnergySouth pension plans. Pursuant to the provisions of the Missouri Utilities’ and Spire Alabama’s pension plans, pension obligations may be satisfied by monthly annuities, lump-sum cash payments, or special termination benefits. Lump-sum payments are recognized as settlements (which can result in gains or losses) only if the total of such payments exceeds 100% of the sum of service and interest costs in a specific year. Special termination benefits, when offered, are also recognized as settlements which can result in gains or losses. Two Spire Alabama plans and one Spire Missouri plan met the criteria for settlement recognition in the fiscal year ended September 30, 2017 , requiring re-measurement of the obligation under those plans using updated census data and assumptions for discount rate and mortality. Lump-sum payments recognized as settlements during fiscal years 2017 , 2016 , and 2015 were $62.2 ( $43.5 attributable to Spire Missouri and $18.7 to Spire Alabama), $16.6 (attributable to Spire Alabama), and $71.1 ( $58.2 attributable to Spire Missouri and $12.9 to Spire Alabama), respectively. Pursuant to a MoPSC Order, the return on plan assets is based on the market-related value of plan assets implemented prospectively over a four -year period. Gains or losses not yet includible in pension cost are amortized only to the extent that such gain or loss exceeds 10% of the greater of the projected benefit obligation or the market-related value of plan assets. Such excess is amortized over the average remaining service life of active participants. The recovery in rates for Spire Missouri East’s qualified pension plan is based on an annual allowance of $15.5 effective January 1, 2011. The recovery in rates for Spire Missouri West’s qualified pension plan is based on an annual allowance of approximately $10 effective February 20, 2010. The difference between these amounts and pension expense as calculated pursuant to the above and that otherwise would be included in the statements of income and statements of comprehensive income is deferred as a regulatory asset or regulatory liability. The following table shows the reconciliation of the beginning and ending balances of the pension benefit obligation at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Benefit obligation, beginning of year $ 794.7 $ 652.3 $ 560.0 $ 497.6 $ 174.3 $ 154.7 Service cost 20.5 15.3 12.7 10.0 6.2 5.3 Interest cost 27.9 28.0 19.5 21.7 6.1 6.3 Actuarial (gain) loss (0.9 ) 85.8 (0.5 ) 59.2 1.6 26.6 Plan amendments (20.7 ) 5.1 — 5.1 (20.7 ) — Spire EnergySouth acquisition — 60.4 — — — — Settlement loss 14.6 1.1 12.2 — 2.4 1.1 Special termination benefits 0.9 1.6 — 1.6 — — Settlement benefits paid (62.2 ) (16.6 ) (43.5 ) — (18.7 ) (16.6 ) Regular benefits paid (26.0 ) (38.3 ) (20.8 ) (35.2 ) (3.0 ) (3.1 ) Benefit obligation, end of year $ 748.8 $ 794.7 $ 539.6 $ 560.0 $ 148.2 $ 174.3 Accumulated benefit obligation, end of year $ 701.4 $ 724.5 $ 500.4 $ 517.7 $ 142.8 $ 149.8 The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Fair value of plan assets, beginning of year $ 540.5 $ 448.9 $ 395.7 $ 339.9 $ 100.0 $ 109.0 Actual return on plan assets 38.0 75.1 25.1 64.4 7.7 10.7 Employer contributions 41.3 26.6 29.4 26.6 11.9 — Spire EnergySouth acquisition — 44.8 — — — — Settlement benefits paid (62.2 ) (16.6 ) (43.5 ) — (18.7 ) (16.6 ) Regular benefits paid (26.0 ) (38.3 ) (20.8 ) (35.2 ) (3.0 ) (3.1 ) Fair value of plan assets, end of year $ 531.6 $ 540.5 $ 385.9 $ 395.7 $ 97.9 $ 100.0 Funded status of plans, end of year $ (217.2 ) $ (254.2 ) $ (153.7 ) $ (164.3 ) $ (50.3 ) $ (74.3 ) The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Current liabilities $ (0.5 ) $ (0.6 ) $ (0.5 ) $ (0.6 ) $ — $ — Noncurrent liabilities (216.7 ) (253.6 ) (153.2 ) (163.7 ) (50.3 ) (74.3 ) Total $ (217.2 ) $ (254.2 ) $ (153.7 ) $ (164.3 ) $ (50.3 ) $ (74.3 ) Pre-tax amounts recognized in accumulated other comprehensive loss not yet recognized as components of net periodic pension cost consist of: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Net actuarial loss $ 163.0 $ 179.4 $ 126.2 $ 135.5 $ 40.9 $ 43.9 Prior service (credit) cost (13.4 ) 8.2 7.3 8.2 (20.7 ) — Subtotal 149.6 187.6 133.5 143.7 20.2 43.9 Adjustments for amounts included in regulatory assets (147.1 ) (184.8 ) (131.0 ) (140.9 ) (20.2 ) (43.9 ) Total $ 2.5 $ 2.8 $ 2.5 $ 2.8 $ — $ — At September 30, 2017 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic pension cost during fiscal 2018 : Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ 12.6 $ 10.5 $ 2.1 Amortization of prior service (credit) cost (0.9 ) 0.9 (1.8 ) Subtotal 11.7 11.4 0.3 Regulatory adjustment (11.4 ) (11.1 ) (0.3 ) Total $ 0.3 $ 0.3 $ — The assumptions used to calculate net periodic pension costs for Spire Missouri are as follows: 2017 2016 2015 Weighted average discount rate - Spire Missouri East plans 3.50% 4.40% 4.30% Weighted average discount rate - Spire Missouri West plans 3.50% 4.50% 4.45% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 7.75% 7.75% 7.75% The assumptions used to calculate net periodic pension costs for Spire Alabama are as follows: 2017 2016 2015 Weighted average discount rate 3.45%/3.50% 4.25%/4.30% 4.15%/4.25% Weighted average rate of future compensation increase 3.00% 3.00% 2.92% Expected long-term rate of return on plan assets 7.25% 7.50% 7.00%/7.25% The weighted average discount rate is based on long-term, high quality bond indices at the measurement date. The expected long-term rate of return on plan assets is based on historical and projected rates of return for current and planned asset classes in the investment portfolio. Assumed projected rates of return for each asset class were selected after analyzing historical experience and future expectations of the returns. The overall expected rate of return for the portfolio was developed based on the target allocation for each class. The assumptions used to calculate the benefit obligations are as follows: 2017 2016 Weighted average discount rate - Spire Missouri East plans 3.75% 3.50% Weighted average discount rate - Spire Missouri West plans 3.70% 3.50% Weighted average discount rate - Spire Alabama plans 3.65%/3.70% 3.45%/3.50% Weighted average rate of future compensation increase 3.00% 3.00% Following are the year-end projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for plans that have a projected benefit obligation and an accumulated benefit obligation in excess of plan assets: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Projected benefit obligation $ 748.8 $ 794.7 $ 539.6 $ 560.0 $ 148.2 $ 174.3 Accumulated benefit obligation 701.4 724.5 500.4 517.7 142.8 149.8 Fair value of plan assets 531.6 540.5 385.9 395.7 97.9 100.0 Following are the targeted and actual plan assets by category as of September 30 of each year for Spire Missouri and Spire Alabama: Spire Missouri 2017 2017 2016 2016 Equity markets 56.4 % 56.8 % 56.2 % 56.9 % Debt securities 43.6 % 42.0 % 43.8 % 43.1 % Cash equivalents — % 1.2 % — % — % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Alabama 2017 2017 2016 2016 Equity markets 60.0 % 58.5 % 60.0 % 59.2 % Debt securities 29.0 % 28.7 % 29.0 % 28.8 % Other* 11.0 % 12.8 % 11.0 % 12.0 % Total 100.0 % 100.0 % 100.0 % 100.0 % * Includes cash and funds invested in real estate, commodities, natural resources and inflation-protected securities. Spire Missouri’s investment policies are designed to maximize, to the extent possible, the funded status of the plans over time, and minimize volatility of funding and costs. The policy seeks to maximize investment returns consistent with these objectives and Spire Missouri’s tolerance for risk. The duration of plan liabilities and the impact of potential changes in asset values on the funded status are fundamental considerations in the selection of plan assets. Outside investment management specialists are utilized in each asset class. Such specialists are provided with guidelines, where appropriate, designed to ensure that the investment portfolio is managed in accordance with the policy. The policy seeks to avoid significant concentrations of risk by investing in a diversified portfolio of assets, currently including a growth (equity) component and a liability-driven (debt) component. Investments in corporate, US government and agencies, and, to a lesser extent, international debt securities seek to provide duration matching with plan liabilities, and typically have investment grade ratings and reflect allocations across various entities and industries. There are also exposures to additional asset types in the target portfolio: commodities, real estate and inflation-indexed securities. For the Missouri East plan, the investment policy permits the use of derivative instruments, which may be used to achieve the desired market exposure of an index, adjust portfolio duration, or rebalance the total portfolio to the target asset allocation. The growth strategy utilizes a combination of derivative instruments and debt securities to achieve diversified exposure to equity and other markets while generating returns from the fixed-income investments and providing further duration matching with the liabilities. Performance and compliance with the guidelines is regularly monitored. The policy calls for increased allocations to debt securities as the funded status improves. Spire Alabama employs a total return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets with a prudent level of risk. Risk tolerance is established through consideration of plan liabilities, plan funded status, corporate financial condition and market conditions. Spire Alabama has developed an investment strategy that focuses on asset allocation, diversification and quality guidelines. The investment goals are to obtain an adequate level of return to meet future obligations of the plans by providing above average risk-adjusted returns with a risk exposure in the mid-range of comparable funds. Investment managers are retained by Spire Alabama to manage separate pools of assets. Funds are allocated to such managers in order to achieve an appropriate, diversified, and balanced asset mix. Comparative market and peer group benchmarks are utilized to ensure that investment managers are performing satisfactorily. Spire Alabama seeks to maintain an appropriate level of diversification to minimize the risk of large losses in a single asset class. Accordingly, plan assets for the pension plans do not have a concentration of assets in a single entity, industry, country, commodity or class of investment fund. Following are expected pension benefit payments for the succeeding five fiscal years, and in aggregate for the five fiscal years thereafter, for Spire, Spire Missouri, and Spire Alabama: 2018 2019 2020 2021 2022 2023- 2027 Spire $ 63.5 $ 63.2 $ 63.2 $ 58.1 $ 57.9 $ 281.1 Spire Missouri 50.7 49.5 49.1 43.5 42.1 198.1 Spire Alabama 10.3 11.1 11.5 11.9 13.0 67.8 The funding policy of Spire Missouri and Spire Alabama is to contribute an amount not less than the minimum required by government funding standards, nor more than the maximum deductible amount for federal income tax purposes. Spire Missouri contributions to the pension plans in fiscal 2018 are anticipated to be $35.5 into the qualified trusts, and $0.5 into the non-qualified plans. Spire Alabama had no required contributions to the qualified pension plans during 2017. Additionally, it is not anticipated that the funded status of the qualified pension plans will fall below statutory thresholds requiring accelerated funding or constraints on benefit levels or plan administration. During fiscal 2017, Spire Alabama made discretionary contributions to the qualified pension plans totaling $11.9; none are expected in fiscal 2018. Postretirement Benefits The Utilities provide certain life insurance benefits at retirement. Spire Missouri plans provide for medical insurance after early retirement until age 65 . For retirements prior to January 1, 2015, the Spire Missouri West plans provided medical insurance after retirement until death. For retirements after January 1, 2015, the Spire Missouri West plans provide medical insurance after early retirement until age 65 . Under the Spire Alabama plans, medical insurance is currently available upon retirement until death for certain retirees depending on the type of employee and the date the employee was originally hired. Net periodic postretirement benefit costs consist of the following components: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Service cost – benefits earned during the period $ 11.0 $ 10.9 $ 12.8 $ 10.4 $ 10.6 $ 12.3 $ 0.3 $ 0.3 $ 0.5 Interest cost on accumulated postretirement benefit obligation 8.6 10.2 11.2 6.8 8.1 8.6 1.6 2.1 2.6 Expected return on plan assets (13.6 ) (13.5 ) (13.2 ) (9.0 ) (8.5 ) (8.1 ) (4.4 ) (5.0 ) (5.1 ) Amortization of prior service cost (credit) — 0.3 0.8 0.2 0.3 0.8 (0.2 ) — — Amortization of actuarial loss (gain) 2.5 3.6 5.1 2.6 3.8 5.1 (0.1 ) (0.2 ) — Special termination benefits — 2.6 — — 2.6 — — — — Subtotal 8.5 14.1 16.7 11.0 16.9 18.7 (2.8 ) (2.8 ) (2.0 ) Regulatory adjustment (3.2 ) (6.6 ) (11.0 ) (1.5 ) (4.8 ) (9.2 ) (1.8 ) (1.8 ) (1.8 ) Net postretirement benefit cost $ 5.3 $ 7.5 $ 5.7 $ 9.5 $ 12.1 $ 9.5 $ (4.6 ) $ (4.6 ) $ (3.8 ) Other changes in plan assets and postretirement benefit obligations recognized in OCI include the following: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Current year actuarial (gain) loss $ (34.1 ) $ 0.8 $ (8.5 ) $ (28.5 ) $ 1.4 $ (2.4 ) $ (4.5 ) $ (0.6 ) $ (6.1 ) Amortization of actuarial (loss) gain (2.5 ) (3.6 ) (5.1 ) (2.6 ) (3.8 ) (5.1 ) 0.1 0.2 — Current year prior service credit (1.4 ) (1.8 ) (4.9 ) — — (4.9 ) (1.4 ) (1.8 ) — Amortization of prior service (cost) credit — (0.3 ) (0.8 ) (0.2 ) (0.3 ) (0.8 ) 0.2 — — Subtotal (38.0 ) (4.9 ) (19.3 ) (31.3 ) (2.7 ) (13.2 ) (5.6 ) (2.2 ) (6.1 ) Regulatory adjustment 38.0 4.9 19.3 31.3 2.7 13.2 5.6 2.2 6.1 Total recognized in OCI $ — $ — $ — $ — $ — $ — $ — $ — $ — Pursuant to a MoPSC Order, the return on plan assets is based on the market-related value of plan assets implemented prospectively over a four -year period. Gains and losses not yet includible in postretirement benefit cost are amortized only to the extent that such gain or loss exceeds 10% of the greater of the accumulated postretirement benefit obligation or the market-related value of plan assets. Such excess is amortized over the average remaining service life of active participants. The recovery in rates for Spire Missouri’s postretirement benefit plans is based on an annual allowance of $9.5 effective January 1, 2011. The difference between these amounts and postretirement benefit cost based on the above and that otherwise would be included in the statements of income and statements of comprehensive income is deferred as a regulatory asset or regulatory liability. The following table sets forth the reconciliation of the beginning and ending balances of the postretirement benefit obligation at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Benefit obligation, beginning of year $ 259.2 $ 239.2 $ 207.9 $ 191.9 $ 45.4 $ 47.3 Service cost 11.0 10.9 10.4 10.6 0.3 0.3 Interest cost 8.6 10.2 6.8 8.1 1.6 2.1 Actuarial (gain) loss (22.1 ) 7.1 (20.9 ) 6.7 — 0.4 Plan amendments (1.4 ) (1.8 ) — — (1.4 ) (1.8 ) Spire EnergySouth acquisition — 5.9 — — — — Special termination benefits — 2.6 — 2.6 — — Curtailments 0.4 — — — — — Retiree drug subsidy program 0.3 0.2 0.3 — — 0.2 Gross benefits paid (17.5 ) (15.1 ) (12.0 ) (12.0 ) (5.3 ) (3.1 ) Benefit obligation, end of year $ 238.5 $ 259.2 $ 192.5 $ 207.9 $ 40.6 $ 45.4 The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Fair value of plan assets at beginning of year $ 246.4 $ 223.3 $ 159.7 $ 143.6 $ 82.8 $ 79.7 Actual return on plan assets 26.2 19.9 16.8 13.8 8.9 6.2 Employer contributions 10.4 14.3 10.4 14.3 — — Spire EnergySouth acquisition — 4.0 — — — — Gross benefits paid (17.5 ) (15.1 ) (12.0 ) (12.0 ) (5.3 ) (3.1 ) Fair value of plan assets, end of year $ 265.5 $ 246.4 $ 174.9 $ 159.7 $ 86.4 $ 82.8 Funded status of plans, end of year $ 27.0 $ (12.8 ) $ (17.6 ) $ (48.2 ) $ 45.8 $ 37.4 The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Current assets $ 1.4 $ 0.3 $ 1.4 $ 0.3 $ — $ — Noncurrent assets 47.0 37.4 1.2 — 45.8 37.4 Current liabilities (0.4 ) (0.4 ) (0.4 ) (0.4 ) — — Noncurrent liabilities (21.0 ) (50.1 ) (19.8 ) (48.1 ) — — Total $ 27.0 $ (12.8 ) $ (17.6 ) $ (48.2 ) $ 45.8 $ 37.4 Pre-tax amounts recognized in accumulated other comprehensive loss not yet recognized as components of net periodic postretirement benefit cost consist of: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Net actuarial loss (gain) $ 1.5 $ 38.0 $ 12.3 $ 43.4 $ (9.7 ) $ (5.4 ) Prior service credit (6.6 ) (5.2 ) (3.7 ) (3.4 ) (2.9 ) (1.8 ) Subtotal (5.1 ) 32.8 8.6 40.0 (12.6 ) (7.2 ) Adjustments for amounts included in regulatory assets 5.1 (32.8 ) (8.6 ) (40.0 ) 12.6 7.2 Total $ — $ — $ — $ — $ — $ — At September 30, 2017 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic postretirement benefit cost during fiscal 2018: Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ 0.9 $ 0.9 $ — Amortization of prior service (credit) cost (0.1 ) 0.3 (0.4 ) Subtotal 0.8 1.2 (0.4 ) Regulatory adjustment (0.8 ) (1.2 ) 0.4 Total $ — $ — $ — The assumptions used to calculate net periodic postretirement benefit costs for Spire Missouri are as follows: 2017 2016 2015 Weighted average discount rate - Spire Missouri East plans 3.15% 4.00% 4.15% Weighted average discount rate - Spire Missouri West plans 3.45% 4.30% 4.40% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets - Spire Missouri East plans 5.75%/7.75% 6.00%/7.75% 6.25%/7.75% Expected long-term rate of return on plan assets - Spire Missouri West plans 5.50% 4.75% 5.00% The assumptions used to calculate net periodic postretirement benefit costs for Spire Alabama are as follows: 2017 2016 2015 Weighted average discount rate 3.60% 4.50% 4.40% Expected long-term rate of return on plan assets 4.00%/6.25% 4.50%/7.25% 4.75%/7.50% The weighted average discount rate is based on long-term, high quality bond indices at the measurement date. The expected long-term rate of return on plan assets is based on historical and projected rates of return for current and planned asset classes in the investment portfolio. Assumed projected rates of return for each asset class were selected after analyzing historical experience and future expectations of the returns. The overall expected rate of return for the portfolio was developed based on the target allocation for each class. The assumptions used to calculate the accumulated postretirement benefit obligations are as follows: 2017 2016 Weighted average discount rate - Spire Alabama plans 3.80% 3.60% Weighted average discount rate - Spire Missouri East plans 3.60% 3.15% Weighted average discount rate - Spire Missouri West plans 3.60% 3.45% Weighted average rate of future compensation increase - Spire Missouri East plans 3.00% 3.00% The assumed medical cost trend rates at September 30 are as follows: 2017 2016 Medical cost trend assumed for next year - Spire Missouri 7.25% 7.50% Medical cost trend assumed for next year - Spire Alabama 7.25% 7.50% Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate) 5.00% 5.00% Year the rate reaches the ultimate trend 2023 2023 The following table presents the effects of an assumed 1% change in the assumed medical cost trend rate: Spire Spire Missouri Spire Alabama 1% Increase 1% Decrease 1% Increase 1% Decrease 1% Increase 1% Decrease Net periodic postretirement benefit cost $ 1.7 $ (1.4 ) $ 1.6 $ (1.3 ) $ 0.1 $ (0.1 ) Accumulated postretirement benefit obligation 10.0 (9.2 ) 8.0 (7.4 ) 1.4 (1.3 ) Following are the targeted and actual plan assets by category as of September 30 of each year for Spire Missouri and Spire Alabama: Spire Missouri Target 2017 Actual 2016 Actual Equity securities 60.0 % 59.0 % 59.1 % Debt securities 40.0 % 39.4 % 39.4 % Other (cash and cash equivalents held to make benefit payments) — % 1.6 % 1.5 % Total 100.0 % 100.0 % 100.0 % Spire Alabama Target 2017 Actual 2016 Actual Equity securities 60.0 % 60.1 % 60.5 % Debt securities 40.0 % 39.9 % 39.5 % Total 100.0 % 100.0 % 100.0 % Missouri and Alabama state laws provide for the recovery in rates of costs accrued pursuant to GAAP provided that such costs are funded through an independent, external funding mechanism. Spire Missouri and Spire Alabama have established Voluntary Employees’ Beneficiary Association and Rabbi Trusts as external funding mechanisms. Their investment policies seek to maximize investment returns consistent with their tolerance for risk. Outside investment management specialists are utilized in each asset class. Such specialists are provided with guidelines, where appropriate, designed to ensure that the investment portfolio is managed in accordance with policy. Performance and compliance with the guidelines is regularly monitored. Spire Missouri and Spire Alabama currently invest in mutual funds which are rebalanced periodically to the target allocation. The mutual funds are diversified across US stock and bond markets, and for Spire Alabama, international stock markets. Following are expected postretirement benefit payments for the succeeding five fiscal years, and in aggregate for the five fiscal years thereafter for Spire, Spire Missouri, and Spire Alabama: 2018 2019 2020 2021 2022 2023- 2027 Spire $ 15.0 $ 16.0 $ 17.1 $ 18.3 $ 18.9 $ 101.3 Spire Missouri 11.8 12.8 14.0 15.2 15.9 86.5 Spire Alabama 2.8 2.8 2.8 2.8 2.7 13.0 Spire Missouri’s and Spire Alabama’s funding policy is to contribute amounts to the trusts equal to the periodic benefit cost calculated pursuant to GAAP as recovered in rates. For Spire Missouri, contributions to the postretirement plans in fiscal 2018 are anticipated to be $7.2 to the qualified trusts and $0.2 paid directly to participants from Spire Missouri funds. It is not anticipated that contributions will be made to the Spire Alabama postretirement plans in fiscal 2018 . Other Plans Spire Missouri and Spire Alabama sponsor 401(k) plans that cover substantially all employees. The plans allow employees to contribute a portion of their base pay in accordance with specific guidelines. Spire Missouri provides a match of such contributions within specific limits. The cost of the defined contribution plans of Spire Missouri amounted to $8.4 , $8.2 , and $8.0 for fiscal years 2017 , 2016 , and 2015 , respectively. Spire Alabama also provides a match of employee contributions within specific limits. The cost of the defined contribution plans of Spire Alabama amounted to $2.7 , $2.3 , and $3.0 for fiscal years 2017 , 2016 , and 2015 , respectively. Fair Value Measurements of Pension and Other Postretirement Plan Assets Spire The table below categorizes the fair value measurements of the Spire pension plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 37.3 $ — $ — $ 37.3 Equity mutual funds - domestic 42.1 25.4 — 67.5 Equity mutual funds - international 37.4 11.2 — 48.6 Debt securities: US bond mutual funds 34.4 68.5 — 102.9 US government 33.2 4.5 — 37.7 US corporate 183.7 — — 183.7 US municipal 4.2 — — 4.2 International 45.1 7.2 — 52.3 Derivatives and margin (payable) (2.6 ) — — (2.6 ) Total $ 414.8 $ 116.8 $ — $ 531.6 As of September 30, 2016 Cash and cash equivalents $ 51.2 $ — $ — $ 51.2 Stock/bond mutual funds 99.3 26.7 0.1 126.1 Debt securities: US bond mutual funds 23.0 126.0 — 149.0 US government 42.1 3.0 — 45.1 US corporate 137.4 — — 137.4 US municipal 6.3 — — 6.3 International 25.3 — — 25.3 Derivatives and margin (payable) (1.0 ) 1.1 — 0.1 Total $ 383.6 $ 156.8 $ 0.1 $ 540.5 The table below categorizes the fair value measurements of Spire’s postretirement plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 4.0 $ — $ — $ 4.0 US stock/bond mutual funds 174.1 71.7 — 245.8 International fund 1.0 14.7 — 15.7 Total $ 179.1 $ 86.4 $ — $ 265.5 As of September 30, 2016 Cash and cash equivalents $ 4.8 $ — $ — $ 4.8 US stock/bond mutual funds 157.9 68.5 — 226.4 International fund 0.9 14.3 — 15.2 Total $ 163.6 $ 82.8 $ — $ 246.4 Cash and cash equivalents include money market mutual funds valued based on quoted market prices. Fair values of derivative instruments are calculated by investment managers who use valuation models that incorporate observable market inputs. Debt securities are valued based on broker/dealer quotations or by using observable market inputs. The stock and bond mutual funds are valued at the quoted market price of the identical securities. Spire Missouri The table below categorizes the fair value measurements of Spire Missouri’s pension plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 31.7 $ — $ — $ 31.7 Equity mutual funds - domestic — 11.9 — 11.9 Equity mutual funds - international — 5.7 — 5.7 Debt securities: US bond mutual funds — 68.5 — 68.5 US government 33.2 4.5 — 37.7 US corporate 183.7 — — 183.7 US municipal 4.2 — — 4.2 International 45.1 — — 45.1 Derivatives and margin (payable) (2.6 ) — — (2.6 ) Total $ 295.3 $ 90.6 $ — $ 385.9 As of September 30, 2016 Cash and cash equivalents $ 46.5 $ — $ — $ 46.5 Stock/bond mutual funds — 14.8 0.1 14.9 Debt securities: US bond mutual funds — 120.2 — 120.2 US government 42.1 3.0 — 45.1 US corporate 137.4 — — 137.4 US municipal 6.3 — — 6.3 International 25.2 — — 25.2 Derivatives and margin (payable) (1.0 ) 1.1 — 0.1 Total $ 256.5 $ 139.1 $ 0.1 $ 395.7 The table below categorizes the fair value measurements of Spire Missouri’s postretirement plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 3.9 $ — $ — $ 3.9 US stock/bond mutual funds 171.0 — — 171.0 Total $ 174.9 $ — $ — $ 174.9 As of September 30, 2016 Cash and cash equivalents $ 4.6 $ — $ — $ 4.6 US stock/bond mutual funds 155.1 — — 155.1 Total $ 159.7 $ — $ — $ 159.7 Cash and cash equivalents include money market mutual funds valued based on quoted market prices. Fair values of derivative instruments are calculated by investment managers who use valuation models that incorporate observable market inputs. Debt securities are valued based on broker/dealer quotations or by using observable market inputs. The stock and bond mutual funds are valued at the quoted market price of the identical securities. Spire Alabama The table below categorizes the fair value measurements of Spire Alabama’s pension plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 3.4 $ — $ — $ 3.4 Equity mutual funds - domestic 28.4 9.1 — 37.5 Equity mutual funds - international 25.2 3.7 — 28.9 Debt securities: US bond mutual funds 23.2 — — 23.2 International — 4.9 — 4.9 Total $ 80.2 $ 17.7 $ — $ 97.9 As of September 30, 2016 Cash and cash equivalents $ 0.4 $ — $ — $ 0.4 Stock/bond mutual funds 59.0 11.9 — 70.9 Debt securities: US bond mutual funds 23.0 5.7 — 28.7 Total $ 82.4 $ 17.6 $ — $ 100.0 The table below categorizes the fair value measurements of Spire Alabama’s postretirement plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 US stock/bond mutual funds $ — $ 71.7 $ — $ 71.7 International fund — 14.7 — 14.7 Total $ — $ 86.4 $ — $ 86.4 As of September 30, 2016 US stock/bond mutual funds $ — $ 68.5 $ — $ 68.5 International fund — 14.3 — 14.3 Total $ — $ 82.8 $ — $ 82.8 Cash and cash equivalents include money market mutual funds valued based on quoted market prices. Fair values of derivative instruments are calculated by investment managers who use valuation models that incorporate observable market inputs. Debt securities are va

INFORMATION BY OPERATING SEGMEN

INFORMATION BY OPERATING SEGMENT	12 Months Ended
INFORMATION BY OPERATING SEGMENT	Sep. 30, 2017
Segment Reporting [Abstract]
INFORMATION BY OPERATING SEGMENT	INFORMATION BY OPERATING SEGMENT Spire The Company has two reportable segments: Gas Utility and Gas Marketing. The Gas Utility segment is the aggregation of the operations of the Utilities. The Gas Marketing segment includes the results of Spire Marketing, a subsidiary engaged in the non-regulated marketing of natural gas and related activities, and Spire Storage Inc., which utilizes natural gas storage contracts for providing natural gas sales. Other includes: • unallocated corporate items, including certain debt and associated interest costs; • Spire STL Pipeline, a subsidiary of Spire planning construction and operation of a proposed 65-mile FERC regulated pipeline to deliver natural gas into eastern Missouri; and • Spire’s subsidiaries engaged in the operation of a propane pipeline, compression of natural gas and risk management, among other activities. Accounting policies are described in Note 1 , Summary of Significant Accounting Policies. Intersegment transactions include sales of natural gas from Spire Marketing to Spire Missouri, sales of natural gas from Spire Missouri to Spire Marketing, propane transportation services provided by Spire NGL Inc. (formerly Laclede Pipeline Company) to Spire Missouri, and propane storage services provided by Spire Missouri to Spire NGL Inc. Management evaluates the performance of the operating segments based on the computation of net economic earnings. Net economic earnings exclude from reported net income the after-tax impacts of net unrealized gains and losses and other timing differences associated with energy-related transactions. Net economic earnings also exclude the after-tax impacts related to acquisition, divestiture, and restructuring activities. Gas Utility Gas Marketing Other Eliminations Consolidated 2017 Revenues from external customers $ 1,660.0 $ 79.3 $ 1.4 $ — $ 1,740.7 Intersegment revenues 7.9 — 6.3 (14.2 ) — Total Operating Revenues 1,667.9 79.3 7.7 (14.2 ) 1,740.7 Operating Expenses Gas Utility Natural and propane gas 645.9 — — (75.4 ) 570.5 Other operation and maintenance 409.1 — — (4.1 ) 405.0 Depreciation and amortization 153.5 — — — 153.5 Taxes, other than income taxes 137.8 — — — 137.8 Total Gas Utility Operating Expenses 1,346.3 — — (79.5 ) 1,266.8 Gas Marketing and Other * — 74.1 12.8 65.3 152.2 Total Operating Expenses 1,346.3 74.1 12.8 (14.2 ) 1,419.0 Operating Income (Loss) $ 321.6 $ 5.2 $ (5.1 ) $ — $ 321.7 Net Economic Earnings (Loss) $ 181.5 $ 6.8 $ (20.7 ) $ — $ 167.6 Capital Expenditures $ 412.6 $ — $ 25.5 $ — $ 438.1 Gas Utility Gas Marketing Other Eliminations Consolidated 2016 Revenues from external customers $ 1,457.2 $ 78.5 $ 1.6 $ — $ 1,537.3 Intersegment revenues 2.2 — 3.2 (5.4 ) — Total Operating Revenues 1,459.4 78.5 4.8 (5.4 ) 1,537.3 Operating Expenses Gas Utility Natural and propane gas 539.7 — — (47.5 ) 492.2 Other operation and maintenance 379.3 — — (1.8 ) 377.5 Depreciation and amortization 136.9 — — — 136.9 Taxes, other than income taxes 125.2 — — — 125.2 Total Gas Utility Operating Expenses 1,181.1 — — (49.3 ) 1,131.8 Gas Marketing and Other * — 66.7 12.6 43.9 123.2 Total Operating Expenses 1,181.1 66.7 12.6 (5.4 ) 1,255.0 Operating Income (Loss) $ 278.3 $ 11.8 $ (7.8 ) $ — $ 282.3 Net Economic Earnings (Loss) $ 160.3 $ 6.4 $ (17.6 ) $ — $ 149.1 Capital Expenditures $ 291.7 $ — $ 1.6 $ — $ 293.3 Gas Utility Gas Marketing Other Eliminations Consolidated 2015 Revenues from external customers $ 1,891.8 $ 82.9 $ 1.7 $ — $ 1,976.4 Intersegment revenues 4.0 70.5 2.0 (76.5 ) — Total Operating Revenues 1,895.8 153.4 3.7 (76.5 ) 1,976.4 Operating Expenses Gas Utility Natural and propane gas 957.6 — — (75.2 ) 882.4 Other operation and maintenance 391.6 — — (1.0 ) 390.6 Depreciation and amortization 129.9 — — — 129.9 Taxes, other than income taxes 142.1 — — — 142.1 Total Gas Utility Operating Expenses 1,621.2 — — (76.2 ) 1,545.0 Gas Marketing and Other * — 146.6 12.6 (0.3 ) 158.9 Total Operating Expenses 1,621.2 146.6 12.6 (76.5 ) 1,703.9 Operating Income (Loss) $ 274.6 $ 6.8 $ (8.9 ) $ — $ 272.5 Net Economic Earnings (Loss) $ 150.4 $ 4.2 $ (16.3 ) $ — $ 138.3 Capital Expenditures $ 284.4 $ — $ 5.4 $ — $ 289.8 * Operating Expenses for “Gas Marketing and Other” include depreciation and amortization for Gas Marketing ( $0.1 for 2017 , $0.1 for 2016 , and $0.3 for 2015 ) and for Other ( $0.5 for 2017 , $0.5 for 2016 , and $0.6 for 2015 ). Total Assets at End of Year 2017 2016 2015 Gas Utility $ 5,551.2 $ 5,184.7 $ 4,679.3 Gas Marketing 246.2 205.0 160.6 Other 2,239.5 1,836.6 1,554.5 Eliminations (1,490.2 ) (1,161.9 ) (1,116.8 ) Total Assets $ 6,546.7 $ 6,064.4 $ 5,277.6 Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings 2017 2016 2015 Net Income $ 161.6 $ 144.2 $ 136.9 Adjustments, pre-tax: Unrealized loss (gain) on energy-related derivatives 6.0 (0.1 ) (2.8 ) Lower of cost or market inventory adjustments — 0.2 0.4 Realized (gain) loss on economic hedges prior to the sale of the physical commodity (0.3 ) (1.6 ) 2.4 Acquisition, divestiture and restructuring activities 4.0 9.2 9.8 Gain on sale of property — — (7.6 ) Income tax effect of adjustments (3.7 ) (2.8 ) (0.8 ) Net Economic Earnings $ 167.6 $ 149.1 $ 138.3

REGULATORY MATTERS

REGULATORY MATTERS	12 Months Ended
REGULATORY MATTERS	Sep. 30, 2017
Regulated Operations [Abstract]
REGULATORY MATTERS	REGULATORY MATTERS The Utilities account for regulated operations in accordance with ASC Topic 980, “Regulated Operations.” This Topic sets forth the application of GAAP for those companies whose rates are established by or are subject to approval by an independent third-party regulator. The provisions of this accounting guidance require, among other things, that financial statements of a regulated enterprise reflect the actions of regulators, where appropriate. These actions may result in the recognition of revenues and expenses in time periods that are different than non-regulated enterprises. When this occurs, costs are deferred as assets in the balance sheet (regulatory assets) and recorded as expenses when those amounts are reflected in rates. Also, regulators can impose liabilities upon a regulated company for amounts previously collected from customers and for recovery of costs that are expected to be incurred in the future (regulatory liabilities). The following regulatory assets and regulatory liabilities were reflected in the Balance Sheets as of September 30, 2017 and 2016 . Unamortized Purchased Gas Adjustments are also included below, which are reported separately in the current assets and liabilities sections of each balance sheet. Spire Spire Missouri Spire Alabama September 30 2017 2016 2017 2016 2017 2016 Regulatory Assets: Current: Pension and postretirement benefit costs $ 42.2 $ 27.0 $ 34.9 $ 20.2 $ 7.2 $ 6.8 Unamortized purchased gas adjustments 102.6 49.7 57.4 43.1 45.2 5.6 Other 30.7 17.2 3.3 3.7 12.2 8.1 Total Current Regulatory Assets 175.5 93.9 95.6 67.0 64.6 20.5 Noncurrent: Future income taxes due from customers 170.5 151.3 170.5 151.3 — — Pension and postretirement benefit costs 404.7 487.9 322.7 375.7 72.6 98.9 Cost of removal 123.3 130.6 — — 123.3 130.6 Unamortized purchased gas adjustments 9.9 12.6 9.9 12.6 — — Energy efficiency 29.0 25.5 29.0 25.5 — — Other 53.7 30.1 25.7 24.7 1.1 1.2 Total Noncurrent Regulatory Assets 791.1 838.0 557.8 589.8 197.0 230.7 Total Regulatory Assets $ 966.6 $ 931.9 $ 653.4 $ 656.8 $ 261.6 $ 251.2 Regulatory Liabilities: Current: RSE adjustment $ 1.4 $ 7.5 $ — $ — $ 1.4 $ 5.0 Unbilled service margin — 5.9 — — — 5.9 Refundable negative salvage 8.2 9.3 — — 8.2 9.3 Unamortized purchased gas adjustments 1.0 1.7 — — — — Other 12.0 6.2 2.7 1.3 2.4 2.5 Total Current Regulatory Liabilities 22.6 30.6 2.7 1.3 12.0 22.7 Noncurrent: Pension and postretirement benefit costs 32.2 28.9 — — 32.2 28.9 Refundable negative salvage 4.1 9.4 — — 4.1 9.4 Accrued cost of removal 83.8 74.8 54.5 55.1 — — Other 37.1 17.6 26.7 12.2 3.3 3.4 Total Noncurrent Regulatory Liabilities 157.2 130.7 81.2 67.3 39.6 41.7 Total Regulatory Liabilities $ 179.8 $ 161.3 $ 83.9 $ 68.6 $ 51.6 $ 64.4 A portion of the Company’s regulatory assets are not earning a return and are shown in the schedule below: Spire Spire Missouri September 30 2017 2016 2017 2016 Future income taxes due from customers $ 170.5 $ 151.3 $ 170.5 $ 151.3 Pension and postretirement benefit costs 198.5 240.6 198.5 240.6 Other 11.3 12.9 11.3 12.9 Total Regulatory Assets Not Earning a Return $ 380.3 $ 404.8 $ 380.3 $ 404.8 Like all the Company’s regulatory assets, these regulatory assets are expected to be recovered from customers in future rates. The recovery period for the future income taxes due from customers and pension and postretirement benefit costs could be as long as 20 years, based on current Internal Revenue Service guidelines and average remaining service life of active participants, respectively. The other items not earning a return are expected to be recovered over a period not to exceed 15 years , consistent with precedent set by the MoPSC. Spire Alabama does not have any regulatory assets that are not earning a return. Spire Missouri On September 30, 2016 Spire Missouri filed to increase its Infrastructure System Replacement Surcharge (ISRS) revenues by $5.0 for Spire Missouri East and $3.4 for Spire Missouri West, related to ISRS investments from March 2016 through October 2016. On November 29, 2016, MoPSC staff recommended $4.5 and $3.4 for Spire Missouri East and Spire Missouri West, respectively, based on updated filings. On January 3, 2017, the MoPSC held a hearing to decide two issues raised by the Missouri Office of the Public Counsel (OPC) pertaining to the ISRS eligibility of hydrostatic testing done by Spire Missouri West and of the replacement of cast iron main interspersed with portions of plastic pipe. On January 18, 2017, the MoPSC found in favor of the Missouri Utilities on the interspersed plastics issue, but against Spire Missouri West on hydrostatic testing, and issued an order setting the ISRS increases at $4.5 and $3.2 for Spire Missouri East and Spire Missouri West, respectively, bringing total annualized ISRS revenue to $29.5 and $13.4 , respectively. Rates were effective January 28, 2017. On March 3, 2017, the OPC filed an appeal to Missouri’s Western District Court of Appeals of the MoPSC’s decision permitting Spire Missouri to include in the ISRS the replacement of cast iron main interspersed with plastic pipe. The appeal will be heard in November 2017. On February 3, 2017, Spire Missouri filed to increase its ISRS revenues, by $3.3 for Spire Missouri East and $2.9 for Spire Missouri West, related to ISRS investments from November 2016 through February 2017. Following the submission of updated information, on April 4, 2017, MoPSC staff submitted its recommendation for an increase in rates of approximately $3.0 each, for a cumulative total of $32.6 and $16.4 for Spire Missouri East and Spire Missouri West, respectively. On that same date, the OPC again raised an objection to the ISRS eligibility of replacing cast iron main interspersed with portions of plastic. On April 18, 2017, the parties filed with the MoPSC a unanimous stipulation and agreement proposing to apply the judicial outcome of the OPC’s March 3, 2017 appeal on the plastics issue to both the ISRS cases on appeal and the current ISRS cases. The agreement was approved by the MoPSC on April 26, 2017. ISRS rates for each of the two service territories were increased by the MoPSC staff-recommended amounts, effective June 1, 2017. On April 15, 2015, Spire Missouri applied to the MoPSC for a new authorization of long-term financing in the amount of $550.0 . On February 10, 2016, the MoPSC issued an order, by a 3-2 vote, authorizing Spire Missouri financing authority of $300.0 for long-term financings placed any time before September 30, 2018. Spire Missouri filed an application for rehearing, which was denied on March 9, 2016. On March 31, 2016, Spire Missouri filed an appeal with Missouri’s Western District Court of Appeals concerning this matter. The parties filed briefs and oral arguments were heard on November 17, 2016. On May 30, 2017, Missouri’s Western District Court of Appeals issued a decision upholding the MoPSC’s February 10, 2016 Order granting Spire Missouri $300.0 in long-term financing authority. On July 5, 2017, the Court denied Spire Missouri’s request to transfer the case to the Missouri Supreme Court, and on October 5, 2017, the Missouri Supreme Court declined to hear Spire Missouri’s direct appeal. On March 20, 2017, Spire Missouri entered into a bond purchase agreement for $170.0 that was funded on September 15, 2017, and applied against the $300.0 authorization. On April 11, 2017, both Spire Missouri East and Spire Missouri West filed for a general rate case, and did so concurrently as agreed to in GM-2013-0254, as part of the acquisition of Spire Missouri West by Spire Missouri in fiscal 2013. The request for Spire Missouri East represents a net rate increase of $25.5 . With the $32.6 already being billed in ISRS, the total base rate increase request was $58.1 . Spire Missouri West’s request represents a net rate increase of $34.0 . With the $16.4 already being billed in ISRS, the total base rate increase request was $50.4 . The rates were premised upon a 10.35% return on equity and the details of the filing can be found in GR-2017-0215 and GR-2017-0216 for Spire Missouri East and Spire Missouri West, respectively. An evidentiary hearing has been set for December 4 through 15, 2017, with a MoPSC decision expected by February 2018. Missouri statutes require new rates to be effective within 11 months of the filing, or by March 8, 2018. Spire Alabama Spire Alabama is subject to regulation by the APSC which established the Rate Stabilization and Equalization (RSE) rate-setting process in 1983. Spire Alabama’s current RSE order has a term extending beyond September 30, 2018, unless the APSC enters an order to the contrary in a manner consistent with law. In the event of unforeseen circumstances, whether physical or economic, of the nature of force majeure and including a change in control, the APSC and Spire Alabama will consult in good faith with respect to modifications, if any. Effective January 1, 2014, Spire Alabama’s allowed range of return on average common equity is 10.5% to 10.95% with an adjusting point of 10.8% . Spire Alabama is eligible to receive a performance-based adjustment of 5 basis points to the return on equity adjusting point, based on meeting certain customer satisfaction criteria. Under RSE, the APSC conducts quarterly reviews to determine whether Spire Alabama’s return on average common equity at the end of the rate year will be within the allowed range of return. Reductions in rates can be made quarterly to bring the projected return within the allowed range; increases, however, are allowed only once each rate year, effective December 1, and cannot exceed 4% of prior-year revenues. The RSE reduction for the July 31, 2016 quarterly point of test was $4.8 and went into effect October 1, 2016, and for the quarterly point of test at September 30, 2016, Spire Alabama recorded a $2.7 RSE reduction effective December 1, 2016. As part of the annual update for RSE, on November 30, 2016, Spire Alabama filed a reduction for rate year 2017 of $2.5 that also became effective December 1, 2016. There was no RSE reduction for the January 31, 2017 , April 30, 2017 and July 31, 2017 points of test. As of September 30, 2017, Spire Alabama recorded a $2.7 RSE reduction to operating revenues to bring the expected rate of return on average common equity at the end of the year to within the allowed range of return. The inflation-based Cost Control Measure (CCM), established by the APSC, allows for annual increases to operation and maintenance (O&M) expense. The CCM range is Spire Alabama’s 2007 actual rate year O&M expense inflation-adjusted using the June Consumer Price Index For All Urban Consumers each rate year plus or minus 1.75% (Index Range). If rate year O&M expense falls within the Index Range, no adjustment is required. If rate year O&M expense exceeds the Index Range, three-quarters of the difference is returned to customers through future rate adjustments. To the extent rate year O&M is less than the Index Range, Spire Alabama benefits by one-half of the difference through future rate adjustments. Certain items that fluctuate based on situations demonstrated to be beyond Spire Alabama’s control may be excluded from the CCM calculation. As of September 30, 2017, Spire Alabama recorded a CCM benefit of $10.7 for rate year 2017, which will be reflected in rates effective December 1, 2017. The CCM benefit was $7.8 for rate year 2016 and $4.7 for rate year 2015. On June 28, 2010, the APSC approved a reduction in depreciation rates, effective June 1, 2010, and a regulatory liability recorded for Spire Alabama. Refunds from such negative salvage liability will be passed back to eligible customers on a declining basis through lower tariff rates through rate year 2019 pursuant to the terms of the Negative Salvage Rebalancing (NSR) rider. The total amount refundable to customers is subject to adjustments over the remaining period for charges made to the Enhanced Stability Reserve (ESR) and other APSC-approved charges. The refunds are due to a re-estimation of future removal costs provided for through the prior depreciation rates. For fiscal 2017, approximately $6.3 of the customer refund was returned to customers. As of September 30, 2017, $12.3 is remaining to be refunded to customers. The NSR pass back for fiscal 2018 is $8.2 and will be reflected in rates effective December 1, 2017 through March 31, 2018. Spire Alabama has APSC approval for an intercompany revolving credit agreement allowing Spire Alabama to borrow from Spire in a principal amount not to exceed $200.0 at any time outstanding in combination with its bank line of credit, and to loan to Spire in a principal amount not to exceed $25.0 at any time outstanding. Borrowings may be used for the following purposes: (a) meeting increased working capital requirements; (b) financing construction requirements related to additions, extensions, and replacements of the distribution systems; and (c) financing other expenditures that may arise from time to time in the normal course of business. On September 18, 2017, Spire Alabama filed an application with the APSC for authorization to issue and sell $75.0 principal amount of debt and to purchase interest rate derivative instruments for the purpose of locking in favorable interest rates and to include the associated interest charges, issuance costs, fees and any gain or loss resulting from the settlement of such interest rate derivative instruments through rates. The application was approved by the APSC October 3, 2017.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Commitments The Company and the Utilities have entered into contracts with various counterparties, expiring on dates through 2031, for the storage, transportation, and supply of natural gas. Minimum payments required under the contracts in place at September 30, 2017 are estimated at $1,281.8 , $563.9 and $285.6 for the Company, Spire Missouri and Spire Alabama, respectively. Additional contracts are generally entered into prior to or during the heating season of November through April. The Utilities recover their costs from customers in accordance with their PGA clauses or GSA riders. Spire NGL Inc. is providing liquid propane transportation service to Spire Missouri pursuant to an approved FERC tariff and a contractual arrangement with Spire Missouri. In accordance with the terms of that agreement, Spire Missouri is obligated to pay Spire NGL Inc. approximately $1.0 annually, at current rates. The agreement renews at the end of each contract year, unless terminated by either party upon provision of at least six months’ notice. A consolidated subsidiary is a general partner in an unconsolidated partnership that invests in real estate partnerships. The subsidiary and third parties are jointly and severally liable for the payment of mortgage loans in the aggregate outstanding amount of approximately $1.3 incurred in connection with various real estate ventures. Spire has no reason to believe that the other principal liable parties will not be able to meet their proportionate share of these obligations. Spire further believes that the asset values of the real estate properties are sufficient to support these mortgage loans. Leases Aggregate rental expense and annual minimum rental commitments under all leases having an initial or remaining non-cancelable term of more than one year are shown below: Aggregate Rental Expense Minimum Rental Commitments 2017 2016 2015 2018 2019 2020 2021 2022 Later Total Spire $ 9.7 $ 11.9 $ 14.1 $ 10.1 $ 9.3 $ 7.8 $ 6.1 $ 6.0 $ 44.4 $ 83.7 Spire Missouri 4.8 4.3 7.6 2.1 1.3 0.2 0.2 — — 3.8 Spire Alabama 4.6 3.7 4.0 4.0 4.1 3.8 2.1 2.1 2.8 18.9 The lease agreement covering the Company’s primary office space in Missouri extends through January 2035. The lease agreement covering the primary office space of Spire Alabama extends through February 2020. Spire Alabama has an operating lease for additional office space that extends to January 31, 2024. Spire Alabama has subleased all of this additional office space to Energen pursuant to a sublease that expires on December 31, 2019 with an option to extend through January 31, 2024. Amounts in the table above have not been reduced for sublease rentals. For Spire Alabama and Spire, sublease rentals were $2.1 , $2.1 , and $2.1 for fiscal years 2017, 2016, and 2015, and minimum future rentals to be received in fiscal years 2018, 2019, and 2020 are $2.1 , $2.1 , and $0.5 , respectively. Spire Missouri, Spire Alabama and Spire Marketing have other relatively minor rental arrangements that provide for minimum rental payments. Contingencies The Company and Utilities account for environmental liabilities and other contingencies in accordance with accounting standards under the loss contingency guidance of ASC Topic 450, “Contingencies,” when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. The Company and the Utilities own and operate natural gas distribution, transmission, and storage facilities, the operations of which are subject to various environmental laws, regulations, and interpretations. While environmental issues resulting from such operations arise in the ordinary course of business, such issues have not materially affected the Company’s or Utilities’ financial position and results of operations. As environmental laws, regulations, and their interpretations change, the Company or the Utilities may incur additional environmental liabilities that may result in additional costs, which may be material. In addition to matters noted below, the Company, Spire Missouri, and Spire Alabama are involved in other litigation, claims, and investigations arising in the normal course of business. Management, after discussion with counsel, believes that the final outcome will not have a material effect on the statements of income, balance sheets, and statements of cash flows of the Company, Spire Missouri, or Spire Alabama. However, there is uncertainty in the valuation of pending claims and prediction of litigation results. In the natural gas industry, many gas distribution companies have incurred environmental liabilities associated with sites they or their predecessor companies formerly owned or operated where manufactured gas operations took place. The Utilities each have former manufactured gas plant (MGP) operations in their respective service territories. Spire On June 14, 2017, Spire filed a lawsuit against Cellular South, Inc. d/b/a C-Spire in federal district court for the Southern District of Alabama, Civil Action 17-00266-KD-N, seeking a declaratory order that Spire’s SPIRE trademarks do not infringe upon Cellular South’s C-SPIRE trademarks, and that Spire is entitled to federal registration of its trademarks. In prior proceedings before the United States Patent and Trademark Office, Cellular South filed oppositions to Spire’s attempts to register the SPIRE name, the SPIRE logo and the SPIRE LOGO + HANDSHAKE trademarks. In answer to Spire’s lawsuit, Cellular South filed counterclaims alleging infringement and unfair business practices, and seeking a declaration of infringement and that SPIRE marks are not registrable by Spire. On September 11, 2017, a federal district court judge denied Cellular South’s motion for a temporary restraining order and an injunction that would have prohibited Spire from using the SPIRE trademarks in Alabama and Mississippi. After consultation with counsel, the Company does not believe that the final resolution of this matter will have a detrimental impact on the Company’s financial condition or results of operations. Spire Gulf is in the chain of title of one former MGP site which it still owns in Mobile, Alabama. On September 15, 2010, Spire Gulf filed an application to enroll the site into the Alabama Department of Environmental Management’s (ADEM) Voluntary Cleanup Program. This application was accepted by ADEM on November 16, 2010. Investigation and testing have been completed. Spire Gulf received an approved remediation plan from ADEM and the remedial actions under the plan were completed in fiscal 2017. Spire Gulf and the Company do not expect potential liabilities that may arise from remediating this site to have a material impact on their future financial condition or results of operations. Since April 2012, a total of 14 lawsuits have been filed against Spire Gulf in Mobile County Circuit Court alleging that in the first half of 2008, Spire Gulf spilled tert-butyl mercaptan, an odorant added to natural gas for safety reasons, in Eight Mile, Alabama. Eleven of the lawsuits have been settled. The remaining three lawsuits, which include approximately 270 individual plaintiffs, allege nuisance, fraud and negligence causes of actions, and seek unspecified compensatory and punitive damages. The Company has resolved all coverage disputes with its insurance carriers relating to this matter. The Company does not expect potential liabilities that may arise from these lawsuits to have a material impact on its future financial condition or results of operations. Spire Missouri Spire Missouri has identified four former MGP sites in eastern Missouri where costs have been incurred and claims have been asserted: one in Shrewsbury, Missouri and three in the city of St. Louis, Missouri (City). Spire Missouri has enrolled two of the sites in the City in the Missouri Department of Natural Resources Brownfields/Voluntary Cleanup Program (BVCP). The third site in the City is the result of a more recent claim assertion by the United States Environmental Protection Agency (EPA), and such claim is currently being investigated. With regard to the former MGP site located in Shrewsbury, Missouri, Spire Missouri and state and federal environmental regulators agreed upon certain remedial actions to a portion of the site in a 1999 Administrative Order on Consent (AOC), which actions have been completed. On September 22, 2008, EPA Region 7 issued a letter of Termination and Satisfaction terminating the AOC. However, if after this termination of the AOC, regulators require additional remedial actions, or additional claims are asserted, Spire Missouri may incur additional costs. In conjunction with redevelopment of one of the sites located in the City, Spire Missouri and another former owner of the site entered into an agreement (Remediation Agreement) with the City development agencies, the developer, and an environmental consultant that obligates one of the City agencies and the environmental consultant to remediate the site and obtain a No Further Action letter from the Missouri Department of Natural Resources (MDNR). The Remediation Agreement also provides for a release of Spire Missouri and the other former site owner from certain liabilities related to the past and current environmental condition of the site and requires the developer and the environmental consultant to maintain certain insurance coverage, including remediation cost containment, premises pollution liability, and professional liability. The operative provisions of the Remediation Agreement were triggered on December 20, 2010, on which date Spire Missouri and the other former site owner, as full consideration under the Remediation Agreement, paid a small percentage of the cost of remediation of the site. The amount paid by Spire Missouri did not materially impact the financial condition, results of operations, or cash flows of the Company. Spire Missouri has not owned the second site located in the City for many years. In a letter dated June 29, 2011, the Attorney General for the state of Missouri informed Spire Missouri that the MDNR had completed an investigation of the site. The Attorney General requested that Spire Missouri participate in the follow up investigations of the site. In a letter dated January 10, 2012, Spire Missouri stated that it would participate in future environmental response activities at the site in conjunction with other potentially responsible parties (PRPs) that are willing to contribute to such efforts in a meaningful and equitable fashion. Accordingly, Spire Missouri entered into a cost sharing agreement for remedial investigation with other PRPs. Pending MDNR approval, which has not occurred to date, the remedial investigation of the site will begin. Additionally, in correspondence dated November 30, 2016, Region 7 of the EPA has asserted that Spire Missouri is liable under Section 107(a) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) for alleged coal gas waste contamination at a third site in the northern portion of the City on which Spire Missouri operated a MGP. Spire Missouri has not owned or operated the site (also known as Station “B”) for over 70 years. Spire Missouri and the site owner have met with the EPA and reviewed its assertions. Both Spire Missouri and the site owner have notified the EPA that the information and data provided by the EPA to date does not rise to the level of documenting a threat to the public health or environment. As such, Spire Missouri is requesting more information from the EPA, some of which will also be utilized to identify other former owners and operators of the site that could be added as PRPs. To date, Spire Missouri has not received a response from the EPA. Spire Missouri has notified its insurers that it seeks reimbursement for costs incurred in the past and future potential liabilities associated with the MGP sites. While some of the insurers have denied coverage and reserved their rights, Spire Missouri continues to discuss potential reimbursements with them. On March 10, 2015, Spire Missouri received a Section 104(e) information request from EPA Region 7 regarding the former Thompson Chemical/Superior Solvents site in the City. In turn, Spire Missouri issued a Freedom of Information Act (FOIA) request to the EPA on April 3, 2015, in an effort to identify the basis of the inquiry. The FOIA response from the EPA was received on July 15, 2015 and a response was provided to the EPA on August 15, 2015. Spire Missouri has received no further inquiry from the EPA regarding this matter. In its western service area, Spire Missouri has seven owned MGP sites enrolled in the BVCP: Joplin MGP #1, St. Joseph MGP #1, Kansas City Coal Gas Station B, Kansas City Station A Railroad area, Kansas City Coal Gas Station A North, Kansas City Coal Gas Station A South, and Independence MGP #2. Source removal has been conducted at all of the owned sites since 2003 with the exception of Joplin. On September 15, 2016, a request was made with the MDNR for a restrictive covenant use limitation with respect to Joplin. Remediation efforts at the seven sites are at various stages of completion, ranging from groundwater monitoring and sampling following source removal activities to the aforementioned request in respect to Joplin. As part of its participation in the BVCP, Spire Missouri communicates regularly with the MDNR with respect to its remediation efforts and monitoring activities at these sites. On May 11, 2015, MDNR approved the next phase of investigation at the Kansas City Station A North and Railroad areas. To date, costs incurred for all Spire Missouri MGP sites for investigation, remediation and monitoring these sites have not been material. However, the amount of costs relative to future remedial actions at these and other sites is unknown and may be material. The actual future costs that Spire Missouri may incur could be materially higher or lower depending upon several factors, including whether remediation actions will be required, final selection and regulatory approval of any remedial actions, changing technologies and government regulations, the ultimate ability of other PRPs to pay, the successful completion of remediation efforts required by the Remediation Agreement described above, and any insurance recoveries. In 2013, Spire Missouri retained an outside consultant to conduct probabilistic cost modeling of 19 former MGP sites owned or operated by Spire Missouri. The purpose of this analysis was to develop an estimated range of probabilistic future liability for each site. That analysis, completed in August 2014, provided a range of demonstrated possible future expenditures to investigate, monitor and remediate all 19 MGP sites. Spire Missouri has recorded its best estimate of the probable expenditures that relate to these matters. The amount is not material. Costs associated with environmental remediation activities are accrued when such costs are probable and reasonably estimable. To the extent such costs (less any amounts received from insurance proceeds or as contributions from other PRPs) are incurred prior to a rate case, Spire Missouri would request from the MoPSC authority to defer such costs and collect them in the next rate case. Spire Missouri and the Company do not expect potential liabilities that may arise from remediating these sites to have a material impact on their future financial condition or results of operations. Spire Alabama Spire Alabama is in the chain of title of nine former MGP sites, four of which it still owns, and five former manufactured gas distribution sites, one of which it still owns. Spire Alabama does not foresee a probable or reasonably estimable loss associated with these nine sites. Spire Alabama and the Company do not expect potential liabilities that may arise from remediating these sites to have a material impact on their future financial conditions or results of operations. In 2012, Spire Alabama responded to an EPA Request for Information Pursuant to Section 104 of CERCLA relating to the 35th Avenue Superfund Site located in North Birmingham, Jefferson County, Alabama. Spire Alabama was identified as a PRP under CERCLA for the cleanup of the site or costs the EPA incurs in cleaning up the site. At this point, Spire Alabama has not been provided information that would allow it to determine the extent, if any, of its potential liability with respect to the 35th Avenue Superfund Site and vigorously denies its inclusion as a PRP. On December 17, 2013, an incident occurred at a Housing Authority apartment complex in Birmingham, Alabama that resulted in one fatality, personal injuries and property damage. Spire Alabama cooperated with the National Transportation Safety Board (NTSB) which investigated the incident. The NTSB report of findings was issued on March 30, 2016 and no safety recommendations, fines, or penalties were contained therein. Spire Alabama has been named as a defendant in several lawsuits arising from the incident, and additional lawsuits and claims may be filed against Spire Alabama.

INTERIM FINANCIAL INFORMATION (

INTERIM FINANCIAL INFORMATION (UNAUDITED)	12 Months Ended
INTERIM FINANCIAL INFORMATION (UNAUDITED)	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
INTERIM FINANCIAL INFORMATION (UNAUDITED)	INTERIM FINANCIAL INFORMATION (UNAUDITED) Spire In the opinion of Spire, the quarterly information presented below for fiscal years 2017 and 2016 includes all adjustments (consisting of only normal recurring accruals) necessary for a fair statement of the results of operations for such periods. Variations in consolidated operations reported on a quarterly basis primarily reflect the seasonal nature of the business of the Utilities. Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2017 Total Operating Revenues $ 495.1 $ 663.4 $ 323.5 $ 258.7 Operating Income 89.1 180.4 50.3 1.9 Net Income (Loss) 45.2 108.0 21.7 (13.3 ) Basic Earnings (Loss) Per Share of Common Stock $ 0.99 $ 2.36 $ 0.45 $ (0.28 ) Diluted Earnings (Loss) Per Share of Common Stock $ 0.99 $ 2.36 $ 0.45 $ (0.28 ) Fiscal Year 2016 Total Operating Revenues $ 399.4 $ 609.3 $ 249.3 $ 279.3 Operating Income (Loss) 87.0 167.7 35.3 (7.7 ) Net Income (Loss) 46.9 100.8 10.7 (14.2 ) Basic Earnings (Loss) Per Share of Common Stock $ 1.08 $ 2.32 $ 0.24 $ (0.31 ) Diluted Earnings (Loss) Per Share of Common Stock $ 1.08 $ 2.31 $ 0.24 $ (0.31 ) Spire Missouri In the opinion of Spire Missouri, the quarterly information presented below for fiscal years 2017 and 2016 includes all adjustments (consisting of only normal recurring accruals) necessary for a fair statement of the results of operations for such periods. Variations in operations reported on a quarterly basis primarily reflect their seasonal nature. Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2017 Total Operating Revenues $ 363.6 $ 447.2 $ 198.5 $ 162.6 Operating Income 64.5 90.2 30.5 11.7 Net Income 38.0 57.0 15.5 2.5 Fiscal Year 2016 Total Operating Revenues $ 317.2 $ 446.7 $ 179.3 $ 144.3 Operating Income 65.1 87.0 29.4 5.4 Net Income (Loss) 39.4 54.3 13.9 (1.7 ) Spire Alabama In the opinion of Spire Alabama, the quarterly information presented below for fiscal years 2017 and 2016 includes all adjustments (consisting of only normal recurring accruals) necessary for a fair statement of the results of operations for such periods. Variations in operations reported on a quarterly basis primarily reflect their seasonal nature. Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2017 Total Operating Revenues $ 86.7 $ 158.8 $ 90.5 $ 64.5 Operating Income (Loss) 19.8 78.9 15.5 (8.4 ) Net Income (Loss) 10.3 47.6 7.4 (7.2 ) Fiscal Year 2016 Total Operating Revenues $ 82.3 $ 166.0 $ 74.0 $ 46.2 Operating Income (Loss) 18.9 80.4 9.3 (17.1 ) Net Income (Loss) 9.9 48.1 4.0 (8.8 )

SUMMARY OF SIGNIFICANT ACCOUN29

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION – These notes are an integral part of the accompanying audited financial statements of Spire Inc. presented on a consolidated basis (Spire or the Company), Spire Missouri Inc. (Spire Missouri or the Missouri Utilities) and Spire Alabama Inc. (Spire Alabama). Spire Missouri and Spire Alabama are wholly owned subsidiaries of the Company. Spire Missouri changed its name from Laclede Gas Company on August 30, 2017, and Spire Alabama changed its name from Alabama Gas Corporation on September 1, 2017. Spire Missouri, Spire Alabama and the subsidiaries of Spire EnergySouth Inc. (formerly known as EnergySouth, Inc.) are collectively referred to as the Utilities. The subsidiaries of Spire EnergySouth Inc. (Spire EnergySouth) are Spire Gulf Inc. (Spire Gulf, formerly known as Mobile Gas Service Corporation) and Spire Mississippi Inc. (Spire Mississippi, formerly known as Willmut Gas & Oil Company). The accompanying audited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). Unless otherwise indicated, references to years herein are references to the fiscal years ending September 30 for the Company and its subsidiaries. The consolidated financial position, results of operations, and cash flows of Spire are primarily derived from the financial position, results of operations, and cash flows of the Utilities. In compliance with GAAP, transactions between Spire Missouri and Spire Alabama and their affiliates, as well as intercompany balances on their balance sheets, have not been eliminated from their separate financial statements. The Company’s September 12, 2016 acquisition of Spire EnergySouth is included in the results of operations since the acquisition date and impacts the comparability of the financial statement periods presented for the Company. For a further discussion of the acquisition, see Note 2 , Acquisitions. The Utilities are regulated natural gas distribution utilities. Due to the seasonal nature of the Utilities, the earnings of Spire, Spire Missouri and Spire Alabama are typically concentrated during the heating season of November through April each fiscal year.
USE OF ESTIMATES	USE OF ESTIMATES – The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
SYSTEM OF ACCOUNTS	SYSTEM OF ACCOUNTS – The accounts of the Utilities are maintained in accordance with the Uniform System of Accounts prescribed by the applicable state public service commissions, which systems substantially conform to that prescribed by the Federal Energy Regulatory Commission (FERC).
UTILITY PLANT, DEPRECIATION AND AMORTIZATION	PLANT, AND EQUIPMENT – Utility Plant – Utility plant is stated at original cost. The cost of additions to utility plant includes contracted work, direct labor and materials, allocable overheads, and an allowance for funds used during construction. The costs of units of property retired, replaced, or renewed are removed from utility plant and are charged to accumulated depreciation. Maintenance and repairs of property and replacement and renewal of items determined to be less than units of property are charged to maintenance expenses. For Spire Missouri, utility plant is depreciated on a straight-line basis at rates based on estimated service lives of the various classes of property. In fiscal years 2017 , 2016 and 2015 , annual depreciation and amortization expense averaged 3.0% of the original cost of depreciable and amortizable property. For Spire Alabama, depreciation is provided using the composite method of depreciation on a straight-line basis over the estimated useful lives of utility property at rates approved by the Alabama Public Service Commission (APSC).
ASSET RETIREMENT OBLIGATIONS	ASSET RETIREMENT OBLIGATIONS – Spire, Spire Missouri, and Spire Alabama record legal obligations associated with the retirement of long-lived assets in the period in which the obligations are incurred, if sufficient information exists to reasonably estimate the fair value of the obligations. Obligations are recorded as both a cost of the related long-lived asset and as a corresponding liability. Subsequently, the asset retirement costs are depreciated over the life of the asset and the asset retirement obligations are accreted to the expected settlement amounts. The Company, Spire Missouri and Spire Alabama record asset retirement obligations associated with certain safety requirements to purge and seal gas distribution mains upon retirement, the plugging and abandonment of storage wells and other storage facilities, specific service line obligations, and certain removal and disposal obligations related to components of Spire Missouri’s, Spire Alabama’s and Spire Gulf’s distribution systems and general plant. Asset retirement obligations recorded by Spire’s other subsidiaries are not material. As authorized by the Missouri Public Service Commission (MoPSC) and APSC, Spire Missouri, Spire Alabama and Spire Gulf accrue future asset removal costs associated with their property, plant and equipment even if a legal obligation does not exist. Such accruals are provided for through depreciation expense and are recorded with corresponding credits to regulatory liabilities or regulatory assets. When those utilities retire depreciable utility plant and equipment, they charge the associated original costs to accumulated depreciation and amortization, and any related removal costs incurred are charged to regulatory liabilities or regulatory assets. The difference between removal costs recognized in depreciation rates and the accretion expense and depreciation expense recognized for financial reporting purposes is a timing difference between recovery of these costs in rates and their recognition for financial reporting purposes. Accordingly, these differences are deferred as regulatory liabilities or regulatory assets. In the rate setting process, the regulatory liabilities or regulatory assets are excluded from the rate base upon which those utilities have the opportunity to earn their allowed rates of return. The costs associated with asset retirement obligations of Spire Missouri, Spire Alabama and Spire Gulf are either currently being recovered in rates or are probable of recovery in future rates.
REGULATED OPERATIONS	REGULATED OPERATIONS – The Utilities account for their regulated operations in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 980, “Regulated Operations.” This Topic sets forth the application of GAAP for those companies whose rates are established by or are subject to approval by an independent third-party regulator. The provisions of this accounting guidance require, among other things, that financial statements of a regulated enterprise reflect the actions of regulators, where appropriate. These actions may result in the recognition of revenues and expenses in time periods that are different than non-regulated enterprises. When this occurs, costs are deferred as assets in the balance sheet (regulatory assets) and recorded as expenses when those amounts are reflected in rates. In addition, regulators can impose liabilities upon a regulated company for amounts previously collected from customers and for recovery of costs that are expected to be incurred in the future (regulatory liabilities). Management believes that the current regulatory environment supports the continued use of these regulatory accounting principles and that all regulatory assets and regulatory liabilities are recoverable or refundable through the regulatory process. See additional discussion on regulated operations in Note 15 , Regulatory Matters. As discussed below for Spire Missouri and Spire Alabama, the Purchased Gas Adjustment (PGA) clauses and Gas Supply Adjustment (GSA) riders allow the Utilities to pass through to customers the cost of purchased gas supplies. Regulatory assets and regulatory liabilities related to the PGA clauses and the GSA rider are both labeled Unamortized Purchased Gas Adjustments herein. Spire Missouri As authorized by the MoPSC, the PGA clause allows Spire Missouri to flow through to customers, subject to prudence review by the MoPSC, the cost of purchased gas supplies. To better match customer billings with market natural gas prices, Spire Missouri is allowed to file to modify, on a periodic basis, the level of gas costs in its PGA. Certain provisions of the PGA clause are included below: • Spire Missouri has a risk management policy that allows for the purchase of natural gas derivative instruments with the goal of managing price risk associated with purchasing natural gas on behalf of its customers. The MoPSC clarified that costs, cost reductions, and carrying costs associated with the Utility’s use of natural gas derivative instruments are gas costs recoverable through the PGA mechanism. • The tariffs allow Spire Missouri flexibility to make up to three discretionary PGA changes during each year, in addition to its mandatory November PGA change, so long as such changes are separated by at least two months . • Spire Missouri is authorized to apply carrying costs to all over- or under-recoveries of gas costs, including costs and cost reductions associated with the use of derivative instruments, including cash payments for margin deposits. Spire Missouri East is also authorized to recover gas inventory carrying costs through its PGA rates to recover costs it incurs to finance its investment in gas supplies that are purchased during the storage injection season for sale during the heating season. • The MoPSC approved a plan applicable to Spire Missouri’s gas supply commodity costs under which it retains a portion of cost savings associated with the acquisition of natural gas below an established benchmark level. This gas supply cost management program allows Spire Missouri to retain 10% of cost savings, up to a maximum of $3.0 annually. Spire Missouri did not record any such incentive compensation under the plan during the three fiscal years reported. Incentives recorded under the plan, if any, are included in Gas Utility Operating Revenues on the Consolidated Statements of Income and under Operating Revenues on Spire Missouri’s Statements of Income. Pursuant to the provisions of the PGA clause, the difference between actual costs incurred and costs recovered through the application of the PGA clause are reflected as a deferred charge or credit at the end of the fiscal year. These costs include costs and cost reductions associated with the use of derivative instruments and gas inventory carrying costs, amounts due to or from customers related to operation of the gas supply cost management program, refunds received from the Company’s suppliers in connection with gas supply, transportation, and storage services, and carrying costs on such over- or under-recoveries. At that time, the balance is classified as a current asset or current liability and recovered from, or credited to, customers over an annual period commencing in November. The balance in the current account is amortized as amounts are reflected in customer billings. The PGA clause also provides for the treatment of income from off-system sales and capacity release revenues. Pre-tax income from off-system sales and capacity release revenues is shared with customers, with an estimated amount assumed in PGA rates. The difference between the actual amount allocated to customers for each fiscal year and the estimated amount assumed in PGA rates is recovered from, or credited to, customers over an annual period commencing in the subsequent November. The customer share of such income is determined in accordance with the following tables, shown for each service territory for which the PGA clauses were approved by the MoPSC. Customer Share Company Share Spire Missouri East First $2.0 of pre-tax income* 85% 15% Next $2.0 of pre-tax income 80% 20% Next $2.0 of pre-tax income 75% 25% Amounts of pre-tax income exceeding $6.0 70% 30% * Customer share was set to 85% and company share set to 15% in fiscal 2017. For fiscal 2016 and 2015, the customer share and company share were 100% and 0%, respectively. Spire Missouri West First $1.2 of pre-tax income 85% 15% Next $1.2 of pre-tax income 80% 20% Next $1.2 of pre-tax income 75% 25% Amounts of pre-tax income exceeding $3.6 70% 30% Spire Alabama Spire Alabama’s rate schedules for natural gas distribution charges contain a GSA rider, established in 1993, which permits the pass-through to customers of changes in the cost of gas supply. Spire Alabama’s tariff provides a temperature adjustment mechanism, also included in the GSA rider, which is designed to moderate the impact of departures from normal temperatures on Spire Alabama’s earnings. The temperature adjustment applies primarily to residential, small commercial and small industrial customers. Other non-temperature weather-related conditions that may affect customer usage are not included in the temperature adjustment.
NATURAL GAS AND PROPANE GAS	NATURAL GAS AND PROPANE GAS – For Spire Missouri East, inventory of natural gas in storage is priced on a last in, first out (LIFO) basis and inventory of propane gas in storage is priced on a first in, first out (FIFO) basis. For the rest of the Gas Utility segment, inventory of natural gas in storage is priced on the weighted average cost basis. The replacement cost of Spire Missouri’s natural gas for current use in eastern Missouri at September 30, 2017 and September 30, 2016 was less than the LIFO cost by $20.8 and $11.4 , respectively. The carrying value of the Utilities’ inventory is not adjusted to the lower of cost or market prices because, pursuant to PGA or GSA, actual gas costs are recovered in customer rates. Natural gas and propane gas storage inventory in Spire’s other operating segments is recorded at the lower of average cost or market.
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS – The Spire EnergySouth acquisition was accounted for by Spire using business combination accounting. Under this method, the purchase price paid by the acquirer is allocated to the assets acquired and liabilities assumed as of the acquisition date based on their fair value.
GOODWILL	GOODWILL – Goodwill is measured as the excess of the acquisition-date fair value of the consideration transferred over the amount of acquisition-date identifiable assets acquired net of assumed liabilities. Spire and Spire Missouri evaluate goodwill for impairment as of July 1 of each year, or more frequently if events and circumstances indicate that goodwill might be impaired. At July 1, 2017, 2016 and 2015, Spire and Spire Missouri each applied a quantitative goodwill evaluation model to their reporting units and concluded goodwill was not impaired because the fair value exceeded the carrying amount.
IMPAIRMENT OF LONG-LIVED ASSETS	IMPAIRMENT OF LONG-LIVED ASSETS – Long-lived assets classified as held and used are evaluated for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. Whether impairment has occurred is determined by comparing the estimated undiscounted cash flows attributable to the assets with the carrying value of the assets. If the carrying value exceeds the undiscounted cash flows, the Company recognizes an impairment charge equal to the amount of the carrying value that exceeds the estimated fair value of the assets. In the period in which the Company determines an asset meets held-for-sale criteria, an impairment charge is recorded to the extent the book value exceeds its fair value less cost to sell.
REVENUE RECOGNITION	REVENUE RECOGNITION – The Utilities read meters and bill customers on monthly cycles. The Missouri Utilities, Spire Gulf and Spire Mississippi record their gas utility revenues from gas sales and transportation services on an accrual basis that includes estimated amounts for gas delivered, but not yet billed. The accruals for unbilled revenues are reversed in the subsequent accounting period when meters are actually read and customers are billed. The amounts of accrued unbilled revenues for Spire Missouri at September 30, 2017 and 2016 were $30.1 and $26.1 , respectively. Spire Alabama records natural gas distribution revenues in accordance with the tariff established by the APSC. Unbilled revenue is accrued in an amount equal to the related gas cost, as profit margin is not considered earned until billed. The amounts of accrued unbilled revenues for Spire Alabama at September 30, 2017 and 2016 were $1.9 and $5.9 . Spire’s other subsidiaries, including Spire Marketing, record revenues when earned, either when the product is delivered or when services are performed. In the course of its business, Spire Marketing enters into commitments associated with the purchase or sale of natural gas. Certain of its derivative natural gas contracts are designated as normal purchases or normal sales and, as such, are excluded from the scope of ASC Topic 815, “Derivatives and Hedging.” Those contracts are accounted for as executory contracts and recorded on an accrual basis. Revenues and expenses from such contracts are recorded using a gross presentation. Contracts not designated as normal purchases or normal sales are recorded as derivatives with changes in fair value recognized in earnings in the periods prior to physical delivery. For additional information on derivative instruments, refer to Note 10 , Derivative Instruments and Hedging Activities. Certain of Spire Marketing’s wholesale purchase and sale transactions are classified as trading activities for financial reporting purposes. Under GAAP, revenues and expenses associated with trading activities are presented on a net basis in Gas Marketing operating revenues (or expenses, if negative) in the Consolidated Statements of Income. This net presentation has no effect on operating income or net income.
INCOME TAXES	INCOME TAXES – Spire and its subsidiaries account for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amount of existing assets and liabilities and the respective tax basis and for tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effects on deferred tax assets and liabilities of a change in enacted tax rates is recognized in income or loss for a non-regulated company, and in a regulatory asset or regulatory liability for a regulated company. A valuation allowance is established when it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions in accordance with authoritative guidance. The authoritative guidance addresses the determination of whether tax benefits claimed, or expected to be claimed, on a tax return should be recorded in the financial statements. Spire may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the position will be sustained upon examination by the taxing authority, based on the technical merits of the position. Tax-related interest and penalties, if any, are classified as a liability on the balance sheets.
CASH AND CASH EQUIVALENTS	CASH AND CASH EQUIVALENTS – All highly liquid debt instruments purchased with original maturities of three months or less are considered to be cash equivalents. Such instruments are carried at cost, which approximates market value. Outstanding checks on the Company’s and Utilities’ bank accounts in excess of funds on deposit create book overdrafts (which are funded at the time checks are presented for payment) and are classified as Other in the Current Liabilities section of the balance sheets. Changes in book overdrafts are reflected as Operating Activities in the statements of cash flows.
NATURAL GAS RECEIVABLE	NATURAL GAS RECEIVABLE – Spire Marketing enters into natural gas transactions with natural gas pipeline companies known as park and loan arrangements. Under the terms of the arrangements, Spire Marketing purchases natural gas from a third party and delivers that natural gas to the pipeline company for the right to receive the same quantity of natural gas from the pipeline company at the same location in a future period. These arrangements are accounted for as non-monetary transactions under GAAP and are recorded at the carrying amount. As such, natural gas receivables are reflected on the Consolidated Balance Sheets at cost, which includes related pipeline fees associated with the transactions. In the period that the natural gas is returned to Spire Marketing, concurrent with the sale of the natural gas to a third party, the related natural gas receivable is expensed in the Consolidated Statements of Income. In conjunction with these transactions, Spire Marketing usually enters into New York Mercantile Exchange (NYMEX) and Intercontinental Exchange (ICE) natural gas futures, options, and swap contracts or fixed price sales agreements to protect against market changes in future sales prices. ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS – Trade accounts receivable are recorded at the amounts due from customers, including unbilled amounts. Estimates of the collectability of trade accounts receivable are based on historical trends, age of receivables, economic conditions, credit risk of specific customers, and other factors. Accounts receivable are written off against the allowance for doubtful accounts when they are deemed to be uncollectible. Spire’s provision for uncollectible accounts includes the amortization of previously deferred uncollectible expenses for Spire Missouri and Spire Alabama, as approved by the MoPSC and the APSC
EARNINGS PER COMMON SHARE	EARNINGS PER COMMON SHARE – GAAP requires dual presentation of basic and diluted earnings per share (EPS). EPS is computed using the two-class method, which is an earnings allocation method for computing EPS that treats a participating security as having rights to earnings that would otherwise have been available to common shareholders. Certain of the Company’s stock-based compensation awards pay non-forfeitable dividends to the participants during the vesting period and, as such, are deemed participating securities. Basic EPS is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. Diluted EPS is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding that are increased for additional shares that would be outstanding if potentially dilutive non-participating securities were converted to common shares, pursuant to the treasury stock method. Shares attributable to equity units, non-participating stock options and time-vested restricted stock/units are excluded from the calculation of diluted earnings per share if the effect would be antidilutive. Shares attributable to non-participating performance-contingent restricted stock awards are only included in the calculation of diluted earnings per share to the extent the underlying performance and/or market conditions are satisfied (a) prior to the end of the reporting period or (b) would be satisfied if the end of the reporting period were the end of the related contingency period and the result would be dilutive.
GROSS RECEIPTS AND SALES TAXES	GROSS RECEIPTS AND SALES TAXES – Gross receipts taxes associated with the Company’s natural gas utility services are imposed on the Company, Spire Missouri, and Spire Alabama and billed to its customers. The revenue and expense amounts are recorded gross in the “Operating Revenues” and “Taxes, other than income taxes” lines, respectively, in the statements of income. The following table presents gross receipts taxes recorded as revenues: 2017 2016 2015 Spire $ 84.6 $ 75.5 $ 97.3 Spire Missouri 60.7 57.4 74.5 Spire Alabama 19.5 17.9 22.6 Sales taxes imposed on applicable Spire Alabama and Spire Missouri sales are billed to customers. These amounts are not recorded in the statements of income but are recorded as tax collections payable and included in the “Other” line of the Current Liabilities section of the balance sheets.
TRANSACTIONS WITH AFFILIATES	TRANSACTIONS WITH AFFILIATES – Transactions between affiliates of the Company have been eliminated from the consolidated financial statements of Spire.
GROUP MEDICAL AND WORKERS' COMPENSATION RESERVES	GROUP MEDICAL AND WORKERS’ COMPENSATION RESERVES – The Company self-insures its group medical and workers’ compensation costs and carries stop-loss coverage in relation to medical claims and workers’ compensation claims. Reserves for amounts incurred but not reported are established based on historical cost levels and lags between occurrences and reporting.
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS – Certain assets and liabilities are recognized or disclosed at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). GAAP establishes a fair value hierarchy that prioritizes the inputs used to measure fair value. The levels of the hierarchy are described below: • Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities. • Level 2 – Pricing inputs other than quoted prices included within Level 1, which are either directly or indirectly observable for the asset or liability as of the reporting date. These inputs are derived principally from, or corroborated by, observable market data. • Level 3 – Pricing that is based upon inputs that are generally unobservable that are based on the best information available and reflect management’s assumptions about how market participants would price the asset or liability. Assessment of the significance of a particular input to the fair value measurements may require judgment and may affect the valuation of the asset or liability and its placement within the fair value hierarchy.
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION – The Company measures stock-based compensation awards at fair value at the date of grant and recognizes the compensation cost of the awards over the requisite service period. Effective with the adoption of Accounting Standards Update No. 2016-09 at the beginning of fiscal 2017 (described under New Accounting Pronouncements below), forfeitures are recognized in the period they occur. In fiscal 2016 and fiscal 2015, forfeitures were estimated at the time of grant and revised, when necessary, in subsequent periods when the actual forfeitures differed from those estimates.
NEW ACCOUNTING STANDARDS	NEW ACCOUNTING PRONOUNCEMENTS – In April 2015, the FASB issued Accounting Standards Update (ASU) No. 2015-03, Interest – Imputation of Interest: Simplifying the Presentation of Debt Issuance Costs . Under prior GAAP, debt issuance costs were recorded as a deferred charge (asset), while debt discount and debt premium costs were recorded as a liability adjustment. This amendment requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. Spire, Spire Missouri and Spire Alabama adopted this ASU as of December 31, 2016. Retrospective adjustments have been made to the previous year balance sheets as of September 30, 2016, and the amounts of unamortized debt issuance costs are shown separately on the statements of capitalization. The ASU does not address the presentation of debt issuance costs related to line-of-credit arrangements, and those continue to be reported as deferred charges.

SUMMARY OF SIGNIFICANT ACCOUN30

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	Sep. 30, 2017
Accounting Policies [Abstract]
Schedule of Capital Expenditure Excluded from Statement of Cash Flow	Accrued capital expenditures, shown in the following table, are excluded from capital expenditures in the statements of cash flows. September 30 2017 2016 2015 Spire $ 41.0 $ 30.4 $ 13.4 Spire Missouri 28.9 14.8 9.6 Spire Alabama 9.4 6.8 3.1
Asset retirement obligations	The following table presents a reconciliation of the beginning and ending balances of asset retirement obligations at September 30, as reported in the balance sheets. Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Asset retirement obligations, beginning of year $ 206.4 $ 159.2 $ 75.2 $ 72.4 $ 120.1 $ 86.6 Liabilities incurred during the period 5.5 4.1 0.3 1.2 5.2 2.9 Liabilities settled during the period (4.6 ) (9.5 ) (1.1 ) (1.9 ) (1.9 ) (6.8 ) Accretion 9.1 13.2 3.6 3.5 5.0 9.7 Revisions in estimated cash flows 80.2 27.5 80.6 — — 27.7 Addition of Spire EnergySouth asset retirement obligations — 11.9 — — — — Asset retirement obligations, end of year $ 296.6 $ 206.4 $ 158.6 $ 75.2 $ 128.4 $ 120.1
Off-system sales	Pre-tax income from off-system sales and capacity release revenues is shared with customers, with an estimated amount assumed in PGA rates. The difference between the actual amount allocated to customers for each fiscal year and the estimated amount assumed in PGA rates is recovered from, or credited to, customers over an annual period commencing in the subsequent November. The customer share of such income is determined in accordance with the following tables, shown for each service territory for which the PGA clauses were approved by the MoPSC. Customer Share Company Share Spire Missouri East First $2.0 of pre-tax income* 85% 15% Next $2.0 of pre-tax income 80% 20% Next $2.0 of pre-tax income 75% 25% Amounts of pre-tax income exceeding $6.0 70% 30% * Customer share was set to 85% and company share set to 15% in fiscal 2017. For fiscal 2016 and 2015, the customer share and company share were 100% and 0%, respectively. Spire Missouri West First $1.2 of pre-tax income 85% 15% Next $1.2 of pre-tax income 80% 20% Next $1.2 of pre-tax income 75% 25% Amounts of pre-tax income exceeding $3.6 70% 30%
Changes in the carrying amount of goodwill by reportable segment	The changes in the carrying amount of goodwill by reportable segment were as follows: Gas Utility Gas Marketing Other Total Balance as of September 30, 2014 $ 210.2 $ — $ 727.6 $ 937.8 Adjustments to finalize the acquisition of Spire Alabama — — 8.2 8.2 Balance as of September 30, 2015 210.2 — 735.8 946.0 Acquisition of Spire EnergySouth — — 218.9 218.9 Balance as of September 30, 2016 210.2 — 954.7 1,164.9 Adjustments to finalize the acquisition of Spire EnergySouth — — 6.7 6.7 Balance as of September 30, 2017 $ 210.2 $ — $ 961.4 $ 1,171.6
Schedule of gross receipts taxes	The following table presents gross receipts taxes recorded as revenues: 2017 2016 2015 Spire $ 84.6 $ 75.5 $ 97.3 Spire Missouri 60.7 57.4 74.5 Spire Alabama 19.5 17.9 22.6
Schedule of inter-company transactions	2017 2016 2015 Purchases of natural gas from Spire Marketing $ 74.4 $ 46.3 $ 74.1 Sales of natural gas to Spire Marketing 7.8 1.9 4.0 Transportation services received from Spire NGL Inc. 1.0 1.0 1.0

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
ACQUISITIONS (Tables)	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of consideration paid and amounts of assets acquired and liabilities assumed	The following table summarizes the consideration paid and the amounts of the assets acquired and liabilities assumed at the acquisition date. As originally recorded Measurement period adjustments As adjusted Recognized amounts of identifiable assets acquired and liabilities assumed: Utility plant $ 199.5 $ — $ 199.5 Cash 2.0 — 2.0 Other current assets 17.5 0.2 17.7 Other assets 79.8 (10.7 ) 69.1 Long-term debt (67.0 ) — (67.0 ) Other current liabilities (42.7 ) — (42.7 ) Deferred tax liabilities (35.5 ) — (35.5 ) Other liabilities (52.8 ) — (52.8 ) Total identifiable net assets 100.8 (10.5 ) 90.3 Goodwill 218.9 6.7 225.6 Consideration (cash) $ 319.7 $ (3.8 ) $ 315.9
Schedule of Pro Forma Information	results of operations are included in the Spire statements of income from the date of acquisition, as shown in the following table. 2017 2016 Total Operating Revenues $ 95.5 $ 3.3 Net Income (Loss) 9.4 (0.2 ) Earnings Per Share $ 0.20 $ — The following unaudited pro forma financial information presents Spire’s combined results of operations as though the Spire EnergySouth acquisition had occurred as of the beginning of fiscal 2015. The unaudited pro forma financial information is not necessarily indicative of either future results of operations or results that would have been achieved if the acquisition had occurred as of the earlier date. It includes estimates and assumptions which management believes are reasonable. The timing of integration costs was not changed. 2017 2016 2015 Total Operating Revenues $ 1,740.7 $ 1,632.4 $ 2,081.6 Net Income 161.6 153.9 143.6 Basic Earnings Per Share $ 3.44 $ 3.48 $ 3.32 Diluted Earnings Per Share 3.43 3.46 3.31

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
STOCK-BASED COMPENSATION (Tables)	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Restricted stock and restricted stock unit activity	2017 activity of restricted stock and restricted stock units subject to performance and/or market conditions is presented below: Shares/ Units Weighted Average Grant Date Fair Value Per Share Nonvested at September 30, 2016 510,583 $ 40.37 Granted (maximum shares that can be earned) 196,400 $ 45.01 Vested (78,825 ) $ 42.37 Forfeited (64,128 ) $ 33.03 Nonvested at September 30, 2017 (at maximum) 564,030 $ 42.51 Nonvested at September 30, 2017 (at target) 282,015 $ 56.32 Time-vested restricted stock and stock unit activity for fiscal 2017 is presented below: Shares/ Units Weighted Average Grant Date Fair Value Per Share Nonvested at September 30, 2016 132,779 $ 49.83 Granted 44,090 $ 63.15 Vested (58,200 ) $ 47.67 Forfeited (7,729 ) $ 55.58 Nonvested at September 30, 2017 110,940 $ 55.85
Stock option awards activity	No stock options were granted during fiscal years 2017 , 2016 , and 2015 . There was no stock option activity in fiscal 2017, as all outstanding stock options either vested or forfeited in fiscal 2016.
Significant assumptions used in the Monte Carlo simulations	The significant assumptions used in the Monte Carlo simulations are as follows: 2017 2016 2015 Risk-free interest rate 1.39% 1.14% 0.83% Expected dividend yield of stock — — — Expected volatility of stock 16.3% 15.0% 14.0% Vesting period 2.8 years 2.8 years 2.8 years
Compensation cost recognized for share-based compensation arrangements	The amounts of compensation cost recognized for share-based compensation arrangements are presented below: 2017 2016 2015 Total compensation cost $ 7.4 $ 6.7 $ 6.7 Compensation cost capitalized (3.3 ) (2.2 ) (1.8 ) Compensation cost recognized in net income $ 4.1 $ 4.5 $ 4.9 Income tax benefit recognized in net income (1.5 ) (1.7 ) (1.9 ) Compensation cost recognized in net income, net of income tax $ 2.6 $ 2.8 $ 3.0

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	12 Months Ended
EARNINGS PER COMMON SHARE (Tables)	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Common Share	2017 2016 2015 Basic EPS: Net Income $ 161.6 $ 144.2 $ 136.9 Less: Income allocated to participating securities 0.4 0.5 0.5 Net Income Available to Common Shareholders $ 161.2 $ 143.7 $ 136.4 Weighted Average Shares Outstanding (millions) 46.9 44.1 43.2 Earnings Per Share of Common Stock $ 3.44 $ 3.26 $ 3.16 Diluted EPS: Net Income $ 161.6 $ 144.2 $ 136.9 Less: Income allocated to participating securities 0.4 0.5 0.5 Net Income Available to Common Shareholders $ 161.2 $ 143.7 $ 136.4 Weighted Average Shares Outstanding (millions) 46.9 44.1 43.2 Dilutive Effect of Stock Options, Restricted Stock, and Restricted Stock Units (millions) 0.1 0.2 0.1 Weighted Average Diluted Shares (millions) 47.0 44.3 43.3 Earnings Per Share of Common Stock $ 3.43 $ 3.24 $ 3.16 Outstanding Shares (in millions) Excluded from the Calculation of Diluted EPS Attributable to: Restricted stock and stock units subject to performance and/or market conditions 0.5 0.3 0.3

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
STOCKHOLDERS' EQUITY (Tables)	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Schedule of accumulated other comprehensive income (loss)	The components of accumulated other comprehensive income (loss), net of income taxes, recognized in the balance sheets at September 30 were as follows: Net Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Pension and Other Postretirement Benefit Plans Net Unrealized Losses on Available for Sale Securities Total Spire Balance at September 30, 2015 $ (0.4 ) $ (1.5 ) $ (0.1 ) $ (2.0 ) Other comprehensive loss (1.9 ) (0.3 ) — (2.2 ) Balance at September 30, 2016 (2.3 ) (1.8 ) (0.1 ) (4.2 ) Other comprehensive income (loss) 7.2 0.3 (0.1 ) 7.4 Balance at September 30, 2017 $ 4.9 $ (1.5 ) $ (0.2 ) $ 3.2 Spire Missouri Balance at September 30, 2015 (0.2 ) (1.5 ) — $ (1.7 ) Other comprehensive income (loss) 0.3 (0.3 ) (0.1 ) (0.1 ) Balance at September 30, 2016 0.1 (1.8 ) (0.1 ) (1.8 ) Other comprehensive income (loss) — 0.2 (0.1 ) 0.1 Balance at September 30, 2017 $ 0.1 $ (1.6 ) $ (0.2 ) $ (1.7 )

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
LONG-TERM DEBT (Tables)	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of maturities of long-term debt by fiscal year	Maturities of long-term debt for Spire on a consolidated basis, Spire Missouri and Spire Alabama for the five fiscal years subsequent to September 30, 2017 are as follows: Spire Spire Missouri Spire Alabama 2018 $ 100.0 $ 100.0 $ — 2019 180.0 50.0 — 2020 40.0 — 40.0 2021 55.0 — — 2022 50.0 — 50.0

NOTES PAYABLE AND CREDIT AGRE36

NOTES PAYABLE AND CREDIT AGREEMENTS (Tables)	12 Months Ended
NOTES PAYABLE AND CREDIT AGREEMENTS (Tables)	Sep. 30, 2017
Short-term Debt [Line Items]
Short-term borrowings	Information about Spire’s consolidated short-term borrowings is presented below. Based on average short-term borrowings for the year ended September 30, 2017 , an increase in the average interest rate of 100 basis points would decrease Spire’s pre-tax earnings and cash flows by approximately $4.9 on an annual basis, portions of which may be offset through the application of PGA or GSA carrying costs. Spire Short ‑ term Borrowings 1 Spire Missouri Commercial Paper Borrowings 2 Spire Alabama Total Short ‑t erm Borrowings Year Ended September 30, 2017 Weighted average borrowings outstanding $369.0 $88.5 $28.3 $485.8 Weighted average interest rate 1.3% 0.9% 1.6% 1.2% Range of borrowings outstanding $73.0 - $675.6 $0.0 - $329.7 $0.0 - $102.5 $395.5 - $675.6 As of September 30, 2017 Borrowings outstanding $477.3 $— $— $477.3 Weighted average interest rate 1.5% —% —% 1.5% Year Ended September 30, 2016 Weighted average borrowings outstanding $42.7 $201.0 $30.2 $273.9 Weighted average interest rate 1.6% 0.7% 1.4% 0.9% Range of borrowings outstanding $0.0 - $82.0 $43.0 - $307.2 $0.0 - $82.0 $73.1 - $427.2 As of September 30, 2016 Borrowings outstanding $73.0 $243.7 $82.0 $398.7 Weighted average interest rate 1.8% 0.8% 1.5% 1.1% 1 Spire Short-term Borrowings includes bank line borrowings of Spire Inc. (excluding its subsidiaries) and, since January 1, 2017, commercial paper. Of Spire’s $477.3 borrowings outstanding as of September 30, 2017, $440.0 was used to provide funding to its subsidiaries, including Spire Missouri ( $203.0 ), Spire Alabama ( $169.9 ), Spire EnergySouth and subsidiaries ( $12.9 ), Spire STL Pipeline LLC ( $26.6 ), and others ( $27.6 ). 2 The commercial paper program for Spire Missouri terminated February 2, 2017.
Spire Missouri
Short-term Debt [Line Items]
Short-term borrowings
Spire Alabama
Short-term Debt [Line Items]
Short-term borrowings

FAIR VALUE OF FINANCIAL INSTR37

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	Sep. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments	The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for the Company are as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) As of September 30, 2017 Cash and cash equivalents $ 7.4 $ 7.4 $ 7.4 $ — Short-term debt 477.3 477.3 — 477.3 Long-term debt, including current portion 2,095.0 2,210.3 — 2,210.3 As of September 30, 2016 Cash and cash equivalents $ 5.2 $ 5.2 $ 5.2 $ — Short-term debt 398.7 398.7 — 398.7 Long-term debt, including current portion 2,070.7 2,257.1 — 2,257.1
Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments	The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for Spire Missouri are as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) As of September 30, 2017 Cash and cash equivalents $ 2.5 $ 2.5 $ 2.5 $ — Short-term debt 203.0 203.0 — 203.0 Long-term debt, including current portion 973.9 1,056.9 — 1,056.9 As of September 30, 2016 Cash and cash equivalents $ 2.1 $ 2.1 $ 2.1 $ — Short-term debt 243.7 243.7 — 243.7 Long-term debt 804.1 900.4 — 900.4
Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments	The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for Spire Alabama are as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) As of September 30, 2017 Cash and cash equivalents $ 0.1 $ 0.1 $ 0.1 $ — Short-term debt 169.9 169.9 — 169.9 Long-term debt 247.8 269.4 — 269.4 As of September 30, 2016 Short-term debt $ 82.0 $ 82.0 $ — $ 82.0 Long-term debt, including current portion 247.6 275.5 — 275.5

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
FAIR VALUE MEASUREMENTS (Tables)	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Measured on Recurring Basis	The information presented below categorizes the assets and liabilities in the balance sheets that are accounted for at fair value on a recurring basis in periods subsequent to initial recognition. The mutual funds included in Level 1 are valued based on exchange-quoted market prices of individual securities. The mutual funds included in Level 2 are valued based on the closing net asset value per unit. Derivative instruments included in Level 1 are valued using quoted market prices on the NYMEX. Derivative instruments classified as Level 2 include physical commodity derivatives that are valued using Over-the-Counter Bulletin Board (OTCBB), broker, or dealer quotation services whose prices are derived principally from, or are corroborated by, observable market inputs. Also included in Level 2 are certain derivative instruments that have values that are similar to, and correlate with, quoted prices for exchange-traded instruments in active markets. Derivative instruments included in Level 3 are valued using generally unobservable inputs that are based upon the best information available and reflect management’s assumptions about how market participants would price the asset or liability. There were no material Level 3 balances as of September 30, 2017 or 2016 . The Company’s and the Utilities’ policy is to recognize transfers between the levels of the fair value hierarchy, if any, as of the beginning of the interim reporting period in which circumstances change or events occur to cause the transfer. The mutual funds are included in “Other investments” on the Company’s balance sheets and in “Property and other investments” on Spire Missouri’s balance sheets. Derivative assets and liabilities, including receivables and payables associated with cash margin requirements, are presented net on the balance sheets when a legally enforceable netting agreement exist between the Company or Spire Missouri and the counterparty to the derivative contract. For additional information on derivative instruments, see Note 10 , Derivative Instruments and Hedging Activities. Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of September 30, 2017 ASSETS Gas Utility: US stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — Gasoline and heating oil contracts 0.1 — — — 0.1 Gas Marketing: NYMEX/ICE natural gas contracts 1.3 1.3 — (2.1 ) 0.5 Natural gas commodity contracts — 6.8 0.1 (1.2 ) 5.7 Total $ 23.1 $ 12.2 $ 0.1 $ (6.7 ) $ 28.7 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 1.8 0.3 — (2.1 ) — Natural gas commodity contracts — 8.4 — (1.2 ) 7.2 Other: Interest rate swaps — 0.9 — — 0.9 Total $ 3.7 $ 9.6 $ — $ (5.2 ) $ 8.1 As of September 30, 2016 ASSETS Gas Utility: US stock/bond mutual funds $ 16.8 $ 4.1 $ — $ — $ 20.9 NYMEX/ICE natural gas contracts 5.3 — — (0.4 ) 4.9 Gasoline and heating oil contracts 0.4 — — (0.3 ) 0.1 Gas Marketing: NYMEX/ICE natural gas contracts 0.4 3.4 — (3.4 ) 0.4 Natural gas commodity contracts — 8.7 0.2 (0.9 ) 8.0 Total $ 22.9 $ 16.2 $ 0.2 $ (5.0 ) $ 34.3 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.6 $ — $ — $ (1.6 ) $ — OTCBB natural gas contracts — 0.2 — — 0.2 Gas Marketing: NYMEX/ICE natural gas contracts 3.5 1.6 — (5.1 ) — Natural gas commodity contracts — 2.6 — (0.9 ) 1.7 Other: Interest rate swaps — 3.0 — — 3.0 Total $ 5.1 $ 7.4 $ — $ (7.6 ) $ 4.9
Spire Missouri
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Measured on Recurring Basis	Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of September 30, 2017 ASSETS US stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — Gasoline and heating oil contracts 0.1 — — — 0.1 Total $ 21.8 $ 4.1 $ — $ (3.4 ) $ 22.5 LIABILITIES NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — Total $ 1.9 $ — $ — $ (1.9 ) $ — As of September 30, 2016 ASSETS US stock/bond mutual funds $ 16.8 $ 4.1 $ — $ — $ 20.9 NYMEX/ICE natural gas contracts 5.3 — — (0.4 ) 4.9 Gasoline and heating oil contracts 0.3 — — (0.3 ) — Total $ 22.4 $ 4.1 $ — $ (0.7 ) $ 25.8 LIABILITIES NYMEX/ICE natural gas contracts $ 1.6 $ — $ — $ (1.6 ) $ — OTCBB natural gas contracts — 0.2 — — 0.2 Total $ 1.6 $ 0.2 $ — $ (1.6 ) $ 0.2

DERIVATIVE INSTRUMENTS AND HE39

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)	12 Months Ended
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)	Sep. 30, 2017
Derivative [Line Items]
Derivative Instruments and Hedging Activities	Open NYMEX/ICE natural gas futures and swap positions at September 30, 2017 were as follows: Gas Utility Gas Marketing MMBtu (millions) Avg. Price Per MMBtu MMBtu (millions) Avg. Price Per MMBtu NYMEX/ICE open short futures positions/swap positions Fiscal 2018 — $ — 8.66 $ 3.34 Fiscal 2019 — — 2.07 3.13 NYMEX/ICE open long futures/swap positions Fiscal 2018 14.18 2.98 3.78 3.16 Fiscal 2019 1.68 2.89 1.84 3.02 Fiscal 2020 — — 0.66 2.91 Fiscal 2021 — — 0.28 2.90 Fiscal 2022 — — 0.22 3.00 ICE open short daily swap positions Fiscal 2018 — — 1.32 2.87 ICE open long daily swap positions Fiscal 2018 — — 0.78 2.79 ICE open short basis swap positions Fiscal 2018 — — 14.04 0.10 Fiscal 2019 — — 3.35 0.27 Fiscal 2020 — — 0.31 0.36 ICE open long basis swap positions Fiscal 2018 — — 11.12 0.38 Fiscal 2019 — — 4.51 0.45 Fiscal 2020 — — 0.62 0.45
The Effect of Derivative Instruments on the Statements of Consolidated Income and Statements of Consolidated Comprehensive Income	Effect of Derivative Instruments on the Consolidated Statements of Income and Consolidated Statements of Comprehensive Income Location of Gain (Loss) Recorded in Income 2017 2016 2015 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gas Marketing natural gas contracts $ — $ (0.6 ) $ (4.3 ) Gas Utility gasoline and heating oil contracts 0.1 — (1.2 ) Interest rate swaps 11.4 (3.4 ) — Total $ 11.5 $ (4.0 ) $ (5.5 ) Effective portion of gain (loss) reclassified from AOCI to income: Natural gas contracts Gas Marketing Operating Revenues $ (0.4 ) $ 4.3 $ 1.7 Gas Marketing Operating Expenses 0.1 (4.9 ) (5.2 ) Subtotal (0.3 ) (0.6 ) (3.5 ) Gasoline and heating oil contracts Gas Utility Other Operating Expenses 0.2 (0.5 ) (0.9 ) Interest rate swaps Interest Expense 0.1 — — Total $ — $ (1.1 ) $ (4.4 ) Ineffective portion of gain (loss) on derivatives recognized in income: Natural gas contracts Gas Marketing Operating Revenues $ — $ 0.1 $ — Gas Marketing Operating Expenses — 0.1 (0.5 ) Subtotal — 0.2 (0.5 ) Gasoline and heating oil contracts Gas Utility Other Operating Expenses — 0.1 0.1 Interest rate swaps Interest Expense 0.5 — — Total $ 0.5 $ 0.3 $ (0.4 ) Derivatives Not Designated as Hedging Instruments* Gain (loss) recognized in income on derivatives: Natural gas commodity contracts Gas Marketing Operating Revenues $ 0.7 $ 12.3 $ (1.3 ) NYMEX / ICE natural gas contracts Gas Marketing Operating Revenues (4.4 ) (1.7 ) (9.6 ) Gasoline and heating oil contracts Other Income and (Income Deductions) - Net — — (0.2 ) Total $ (3.7 ) $ 10.6 $ (11.1 ) * Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not designated as hedging instruments for financial reporting purposes, are deferred pursuant to the Missouri Utilities’ PGA clauses and initially recorded as regulatory assets or regulatory liabilities. These gains and losses are excluded from the table above because they have no direct impact on the statements of income. Such amounts are recognized in the statements of income as a component of Regulated Gas Distribution Natural and Propane Gas operating expenses when they are recovered through the PGA clause and reflected in customer billings.
Fair Value of Derivative Instruments in the Consolidated Balance Sheet	Fair Value of Derivative Instruments in the Consolidated Balance Sheets Asset Derivatives* Liability Derivatives* September 30, 2017 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Gas Utility: Gasoline and heating oil contracts Derivative Instrument Assets $ 0.1 Derivative Instrument Assets $ — Gas Marketing: Natural gas contracts Derivative Instrument Assets 0.3 Derivative Instrument Assets 0.2 Deferred Charges – Other 0.3 Deferred Charges – Other — Other: Interest rate swaps Current Liabilities - Other — Current Liabilities - Other 0.9 Subtotal 0.7 1.1 Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Accounts Receivable – Other 3.4 Accounts Receivable – Other 1.9 Gas Marketing: NYMEX / ICE natural gas contracts Derivative Instrument Assets 1.7 Derivative Instrument Assets 1.4 Deferred Charges – Other 0.3 Deferred Charges – Other 0.5 Natural gas commodity Derivative Instrument Assets 5.3 Derivative Instrument Assets 0.1 Other Deferred Charges 0.4 Other Deferred Charges — Current Liabilities – Other 0.8 Current Liabilities – Other 5.0 Deferred Credits – Other 0.4 Deferred Credits – Other 3.3 Subtotal 12.3 12.2 Total derivatives $ 13.0 $ 13.3 September 30, 2016 Derivatives designated as hedging instruments Gas Utility: Gasoline and heating oil contracts Derivative Instrument Assets $ 0.3 Derivative Instrument Assets $ — Gas Marketing: Natural gas contracts Derivative Instrument Assets 2.5 Derivative Instrument Assets 0.8 Deferred Charges - Other 0.4 Deferred Charges - Other 0.1 Other: Interest rate swaps Derivative Instrument Assets — Derivative Instrument Assets 3.0 Subtotal 3.2 3.9 Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Accounts Receivable – Other 5.4 Accounts Receivable – Other 1.6 Derivative Instrument Assets — Derivative Instrument Assets 0.2 Gas Marketing: NYMEX / ICE natural gas contracts Derivative Instrument Assets 0.8 Derivative Instrument Assets 4.1 Deferred Charges – Other — Deferred Charges – Other 0.1 Natural gas commodity Derivative Instrument Assets 6.5 Derivative Instrument Assets 0.2 Other Deferred Charges 2.1 Other Deferred Charges 0.3 Current Liabilities – Other 0.2 Current Liabilities – Other 2.0 Deferred Credits – Other 0.2 Deferred Credits – Other 0.1 Subtotal 15.2 8.6 Total derivatives $ 18.4 $ 12.5 * The fair values of Asset Derivatives and Liability Derivatives exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the balance sheets. As such, the gross balances presented in the table above are not indicative of the Company’s net economic exposure. Refer to Note 9 , Fair Value Measurements, for information on the valuation of derivative instruments.
Derivative instrument Reconciliation	Following is a reconciliation of the amounts in the tables above to the amounts presented in the Consolidated Balance Sheets: 2017 2016 Fair value of asset derivatives presented above $ 13.0 $ 18.4 Fair value of cash margin (payable) receivable offset with derivatives (1.5 ) 2.5 Netting of assets and liabilities with the same counterparty (5.3 ) (7.6 ) Total $ 6.2 $ 13.3 Derivative Instrument Assets, per Consolidated Balance Sheets: Derivative instrument assets $ 5.9 $ 11.4 Deferred Charges – Other 0.3 1.9 Total $ 6.2 $ 13.3 Fair value of liability derivatives presented above $ 13.3 $ 12.5 Netting of assets and liabilities with the same counterparty (5.3 ) (7.6 ) Total $ 8.0 $ 4.9 Derivative Instrument Liabilities, per Consolidated Balance Sheets: Current Liabilities – Other $ 4.9 $ 4.8 Deferred Credits – Other 3.1 0.1 Total $ 8.0 $ 4.9
Spire Missouri
Derivative [Line Items]
Derivative Instruments and Hedging Activities	’s derivative instruments consist primarily of NYMEX positions. The NYMEX is the primary national commodities exchange on which natural gas derivatives are traded. Open NYMEX natural gas futures positions at September 30, 2017 were as follows: MMBtu (millions) Avg. Price Per MMBtu NYMEX/ICE open long futures/swap positions Fiscal 2018 14.18 $ 2.98 Fiscal 2019 1.68 2.89
The Effect of Derivative Instruments on the Statements of Consolidated Income and Statements of Consolidated Comprehensive Income	Effect of Derivative Instruments on the Statements of Income and Statements of Comprehensive Income Location of Gain (Loss) Recorded in Income 2017 2016 2015 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gasoline and heating oil contracts $ 0.1 $ — $ (1.2 ) Effective portion of gain (loss) reclassified from AOCI to income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ 0.2 $ (0.5 ) $ (0.9 ) Ineffective portion of gain (loss) on derivatives recognized in income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ — $ 0.1 $ 0.1 Derivatives Not Designated as Hedging Instruments* Gain (loss) recognized in income on derivatives: Gasoline and heating oil contracts Other Income and (Income Deductions) - Net $ — $ — $ (0.2 ) * Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not designated as hedging instruments for financial reporting purposes, are deferred pursuant to the Spire Missouri’s PGA clauses and initially recorded as regulatory assets or regulatory liabilities. These gains and losses are excluded from the table above because they have no direct impact on the Statements of Income. Such amounts are recognized in the Statements of Income as a component of Regulated Gas Distribution Natural and Propane Gas operating expenses when they are recovered through the PGA clause and reflected in customer billings.
Fair Value of Derivative Instruments in the Consolidated Balance Sheet	Fair Value of Derivative Instruments in the Balance Sheets Asset Derivatives* Liability Derivatives* September 30, 2017 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Gasoline and heating oil contracts Derivative Instrument Assets $ 0.1 Derivative Instrument Assets $ — Derivatives not designated as hedging instruments Natural gas contracts Accounts Receivable – Other 3.4 Accounts Receivable – Other 1.9 Total derivatives $ 3.5 $ 1.9 September 30, 2016 Derivatives designated as hedging instruments Gasoline and heating oil contracts Derivative Instrument Assets $ 0.3 Derivative Instrument Assets $ — Subtotal 0.3 — Derivatives not designated as hedging instruments Natural gas contracts Accounts Receivable – Other 5.4 Accounts Receivable – Other 1.6 OTCBB natural gas contracts Derivative Instrument Assets — Derivative Instrument Assets 0.2 Subtotal 5.4 1.8 Total derivatives $ 5.7 $ 1.8 * The fair values of Asset Derivatives and Liability Derivatives exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the Balance Sheets. As such, the gross balances presented in the table above are not indicative of Spire Missouri’s net economic exposure. Refer to Note 9 , Fair Value Measurements, for information on the valuation of derivative instruments.
Derivative instrument Reconciliation	Following is a reconciliation of the amounts in the tables above to the amounts presented in Spire Missouri’s Balance Sheets: 2017 2016 Fair value of asset derivatives presented above $ 3.5 $ 5.7 Fair value of cash margin (payable) receivable offset with derivatives (1.5 ) 0.8 Netting of assets and liabilities with the same counterparty (1.9 ) (1.6 ) Total $ 0.1 $ 4.9 Derivative Instrument Assets, per Balance Sheets: Derivative instrument assets $ 0.1 $ 4.9 Total $ 0.1 $ 4.9 Fair value of liability derivatives presented above $ 1.9 $ 1.8 Netting of assets and liabilities with the same counterparty (1.9 ) (1.6 ) Total $ — $ 0.2 Derivative Instrument Liabilities, per Balance Sheets: Current Liabilities – Other $ — $ 0.2 Total $ — $ 0.2

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
INCOME TAXES (Tables)	Sep. 30, 2017
Income Tax Contingency [Line Items]
Net Provision For Income Tax	The Company’s provision for income taxes charged during the fiscal years ended September 30, 2017 , 2016 , and 2015 are as follows: 2017 2016 2015 Federal Current $ 0.1 $ 0.1 $ (3.3 ) Deferred 67.7 62.0 58.8 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current 0.5 0.6 — Deferred 9.5 7.0 6.9 Total income tax expense $ 77.6 $ 69.5 $ 62.2
Effective income tax rate variation from stated tax rate	The Company’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2017 2016 2015 Federal income tax statutory rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 2.8 2.8 3.0 Certain expenses capitalized on books and deducted on tax return (2.3 ) (3.4 ) (3.7 ) Taxes related to prior years (0.9 ) (0.2 ) (0.6 ) Other items – net * (2.2 ) (1.7 ) (2.5 ) Effective income tax rate 32.4 % 32.5 % 31.2 % * Other consists primarily of property adjustments.
Significant Items in Net Deferred Tax Liability	The Company’s significant items comprising the net deferred tax liability recorded in the Consolidated Balance Sheets as of September 30 are as follows: 2017 2016 Deferred tax assets: Reserves not currently deductible $ 31.5 $ 21.3 Pension and other postretirement benefits 58.6 68.3 Operating losses 169.6 102.3 Other 26.0 — Deferred tax assets 285.7 191.9 Less: valuation allowance 0.5 0.9 Total deferred tax assets 285.2 191.0 Deferred tax liabilities: Relating to property 728.3 623.1 Regulatory pension and other postretirement benefits 108.0 106.8 Deferred gas costs 30.6 20.0 Other** 125.8 48.4 Total deferred tax liabilities 992.7 798.3 Net deferred tax liability $ 707.5 $ 607.3
Unrecognized Tax Benefit Reconciliation	The following table presents a reconciliation of the beginning and ending balances of the Company’s unrecognized tax benefits: 2017 2016 2015 Unrecognized tax benefits, beginning of year $ 10.0 $ 7.1 $ 4.6 Increases related to tax positions taken in current year 2.4 3.4 2.9 Reductions due to lapse of applicable statute of limitations (1.4 ) (0.5 ) (0.4 ) Unrecognized tax benefits, end of year $ 11.0 $ 10.0 $ 7.1
Spire Missouri
Income Tax Contingency [Line Items]
Net Provision For Income Tax	’s provision for income taxes charged during the fiscal years ended September 30, 2017 , 2016 , and 2015 are as follows: 2017 2016 2015 Federal Current $ — $ — $ (2.1 ) Deferred 42.0 37.5 40.9 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current — 0.1 (0.1 ) Deferred 5.7 8.0 4.7 Total income tax expense $ 47.5 $ 45.4 $ 43.2
Effective income tax rate variation from stated tax rate	’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2017 2016 2015 Federal income tax statutory rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 2.8 2.8 2.8 Certain expenses capitalized on books and deducted on tax return (3.5 ) (4.8 ) (4.9 ) Taxes related to prior years (1.4 ) (0.2 ) (0.8 ) Other items – net * (3.3 ) (2.8 ) (3.0 ) Effective income tax rate 29.6 % 30.0 % 29.1 % * Other consists primarily of property adjustments.
Significant Items in Net Deferred Tax Liability	’s significant items comprising the net deferred tax liability reported in the Balance Sheets as of September 30 are as follows: 2017 2016 Deferred tax assets: Reserves not currently deductible $ 25.3 $ 14.9 Pension and other postretirement benefits 52.7 56.9 Operating losses 52.0 29.9 Deferred tax assets 130.0 101.7 Less: valuation allowance 0.5 0.9 Total deferred tax assets 129.5 100.8 Deferred tax liabilities: Relating to utility property 563.2 497.0 Regulatory pension and other postretirement benefits 108.0 106.8 Deferred gas costs 25.0 20.0 Other 57.1 33.9 Total deferred tax liabilities 753.3 657.7 Net deferred tax liability $ 623.8 $ 556.9
Unrecognized Tax Benefit Reconciliation	The following table presents a reconciliation of the beginning and ending balances of Spire Missouri unrecognized tax benefits: 2017 2016 2015 Unrecognized tax benefits, beginning of year $ 9.7 $ 6.9 $ 4.2 Increases related to tax positions taken in current year 2.4 3.3 2.9 Reductions due to lapse of applicable statute of limitations (1.4 ) (0.5 ) (0.2 ) Unrecognized tax benefits, end of year $ 10.7 $ 9.7 $ 6.9
Spire Alabama
Income Tax Contingency [Line Items]
Net Provision For Income Tax	’s provision for income taxes charged during the fiscal years ended September 30, 2017 , 2016 , and 2015 , are as follows: 2017 2016 2015 Federal Current $ — $ (0.8 ) $ — Deferred 31.6 29.4 25.9 State and local Current — — 0.1 Deferred 4.2 3.8 3.3 Total income tax expense $ 35.8 $ 32.4 $ 29.3
Effective income tax rate variation from stated tax rate	’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2017 2016 2015 Federal income tax statutory rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 2.8 2.8 2.8 Other items – net 0.3 0.1 0.1 Effective income tax rate 38.1 % 37.9 % 37.9 %
Significant Items in Net Deferred Tax Liability	’s significant items comprising the net deferred tax asset reported in the Balance Sheets as of September 30 are as follows: 2017 2016 Deferred tax assets: Reserves not currently deductible $ 6.0 $ 6.3 Pension and other postretirement benefits 4.4 11.4 Goodwill 214.4 233.4 Operating losses 88.3 60.2 Total deferred tax assets 313.1 311.3 Deferred tax liabilities: Relating to utility property 119.3 87.6 Other 8.2 2.3 Total deferred tax liabilities 127.5 89.9 Net deferred tax asset $ 185.6 $ 221.4

PENSION PLANS AND OTHER POSTR41

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Tables)	12 Months Ended
PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Tables)	Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	The table below categorizes the fair value measurements of the Spire pension plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 37.3 $ — $ — $ 37.3 Equity mutual funds - domestic 42.1 25.4 — 67.5 Equity mutual funds - international 37.4 11.2 — 48.6 Debt securities: US bond mutual funds 34.4 68.5 — 102.9 US government 33.2 4.5 — 37.7 US corporate 183.7 — — 183.7 US municipal 4.2 — — 4.2 International 45.1 7.2 — 52.3 Derivatives and margin (payable) (2.6 ) — — (2.6 ) Total $ 414.8 $ 116.8 $ — $ 531.6 As of September 30, 2016 Cash and cash equivalents $ 51.2 $ — $ — $ 51.2 Stock/bond mutual funds 99.3 26.7 0.1 126.1 Debt securities: US bond mutual funds 23.0 126.0 — 149.0 US government 42.1 3.0 — 45.1 US corporate 137.4 — — 137.4 US municipal 6.3 — — 6.3 International 25.3 — — 25.3 Derivatives and margin (payable) (1.0 ) 1.1 — 0.1 Total $ 383.6 $ 156.8 $ 0.1 $ 540.5 The table below categorizes the fair value measurements of Spire’s postretirement plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 4.0 $ — $ — $ 4.0 US stock/bond mutual funds 174.1 71.7 — 245.8 International fund 1.0 14.7 — 15.7 Total $ 179.1 $ 86.4 $ — $ 265.5 As of September 30, 2016 Cash and cash equivalents $ 4.8 $ — $ — $ 4.8 US stock/bond mutual funds 157.9 68.5 — 226.4 International fund 0.9 14.3 — 15.2 Total $ 163.6 $ 82.8 $ — $ 246.4
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic cost	The net periodic pension costs include the following components: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Service cost – benefits earned during the period $ 20.5 $ 15.3 $ 17.3 $ 12.7 $ 10.0 $ 11.5 $ 6.2 $ 5.3 $ 5.8 Interest cost on projected benefit obligation 27.9 28.0 29.5 19.5 21.7 23.3 6.1 6.3 6.2 Expected return on plan assets (38.5 ) (34.9 ) (37.4 ) (28.1 ) (26.7 ) (29.2 ) (7.2 ) (8.2 ) (8.2 ) Amortization of prior service cost 1.0 0.4 0.5 1.0 0.4 0.5 — — — Amortization of actuarial loss 12.5 8.0 7.5 10.7 7.9 7.5 1.8 0.1 — Loss on lump-sum settlements and curtailments 17.9 3.3 19.6 13.5 — 18.0 4.6 3.3 1.6 Special termination benefits 0.9 1.6 — — 1.6 — — — — Subtotal 42.2 21.7 37.0 29.3 14.9 31.6 11.5 6.8 5.4 Regulatory adjustment (2.4 ) 17.8 (2.1 ) (4.1 ) 11.7 (5.2 ) 1.8 6.1 3.1 Net pension cost $ 39.8 $ 39.5 $ 34.9 $ 25.2 $ 26.6 $ 26.4 $ 13.3 $ 12.9 $ 8.5
Other changes in plan assets and benefit obligations recognized in other comprehensive income	Other changes in plan assets and pension benefit obligations recognized in other comprehensive income or loss include the following: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Current year actuarial loss $ 14.1 $ 46.8 $ 48.3 $ 14.8 $ 21.6 $ 26.0 $ 3.3 $ 25.2 $ 22.3 Amortization of actuarial loss (12.5 ) (8.0 ) (7.5 ) (10.7 ) (7.9 ) (7.5 ) (1.8 ) (0.1 ) — Acceleration of loss recognized due to settlement (18.2 ) (3.3 ) (19.6 ) (13.5 ) — (18.0 ) (4.5 ) (3.3 ) (1.6 ) Current year service cost — 5.0 — — 5.0 — — — — Current year prior year service cost (20.7 ) — — — — — (20.7 ) — — Amortization of prior service cost (1.0 ) (0.4 ) (0.5 ) (1.0 ) (0.4 ) (0.5 ) — — — Subtotal (38.3 ) 40.1 20.7 (10.4 ) 18.3 — (23.7 ) 21.8 20.7 Regulatory adjustment 38.0 (39.8 ) (21.2 ) 10.1 (18.0 ) (0.5 ) 23.7 (21.8 ) (20.7 ) Total recognized in OCI $ (0.3 ) $ 0.3 $ (0.5 ) $ (0.3 ) $ 0.3 $ (0.5 ) $ — $ — $ —
Reconciliation of the beginning and ending balances of benefit obligation	The following table shows the reconciliation of the beginning and ending balances of the pension benefit obligation at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Benefit obligation, beginning of year $ 794.7 $ 652.3 $ 560.0 $ 497.6 $ 174.3 $ 154.7 Service cost 20.5 15.3 12.7 10.0 6.2 5.3 Interest cost 27.9 28.0 19.5 21.7 6.1 6.3 Actuarial (gain) loss (0.9 ) 85.8 (0.5 ) 59.2 1.6 26.6 Plan amendments (20.7 ) 5.1 — 5.1 (20.7 ) — Spire EnergySouth acquisition — 60.4 — — — — Settlement loss 14.6 1.1 12.2 — 2.4 1.1 Special termination benefits 0.9 1.6 — 1.6 — — Settlement benefits paid (62.2 ) (16.6 ) (43.5 ) — (18.7 ) (16.6 ) Regular benefits paid (26.0 ) (38.3 ) (20.8 ) (35.2 ) (3.0 ) (3.1 ) Benefit obligation, end of year $ 748.8 $ 794.7 $ 539.6 $ 560.0 $ 148.2 $ 174.3 Accumulated benefit obligation, end of year $ 701.4 $ 724.5 $ 500.4 $ 517.7 $ 142.8 $ 149.8
Fair value of plan assets	The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Fair value of plan assets, beginning of year $ 540.5 $ 448.9 $ 395.7 $ 339.9 $ 100.0 $ 109.0 Actual return on plan assets 38.0 75.1 25.1 64.4 7.7 10.7 Employer contributions 41.3 26.6 29.4 26.6 11.9 — Spire EnergySouth acquisition — 44.8 — — — — Settlement benefits paid (62.2 ) (16.6 ) (43.5 ) — (18.7 ) (16.6 ) Regular benefits paid (26.0 ) (38.3 ) (20.8 ) (35.2 ) (3.0 ) (3.1 ) Fair value of plan assets, end of year $ 531.6 $ 540.5 $ 385.9 $ 395.7 $ 97.9 $ 100.0 Funded status of plans, end of year $ (217.2 ) $ (254.2 ) $ (153.7 ) $ (164.3 ) $ (50.3 ) $ (74.3 )
Amounts recognized in consolidated balance sheets	The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Current liabilities $ (0.5 ) $ (0.6 ) $ (0.5 ) $ (0.6 ) $ — $ — Noncurrent liabilities (216.7 ) (253.6 ) (153.2 ) (163.7 ) (50.3 ) (74.3 ) Total $ (217.2 ) $ (254.2 ) $ (153.7 ) $ (164.3 ) $ (50.3 ) $ (74.3 ) Pre-tax amounts recognized in accumulated other comprehensive loss not yet recognized as components of net periodic pension cost consist of: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Net actuarial loss $ 163.0 $ 179.4 $ 126.2 $ 135.5 $ 40.9 $ 43.9 Prior service (credit) cost (13.4 ) 8.2 7.3 8.2 (20.7 ) — Subtotal 149.6 187.6 133.5 143.7 20.2 43.9 Adjustments for amounts included in regulatory assets (147.1 ) (184.8 ) (131.0 ) (140.9 ) (20.2 ) (43.9 ) Total $ 2.5 $ 2.8 $ 2.5 $ 2.8 $ — $ —
Pre-tax amounts amortized from accumulated other comprehensive income into net periodic cost	At September 30, 2017 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic pension cost during fiscal 2018 : Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ 12.6 $ 10.5 $ 2.1 Amortization of prior service (credit) cost (0.9 ) 0.9 (1.8 ) Subtotal 11.7 11.4 0.3 Regulatory adjustment (11.4 ) (11.1 ) (0.3 ) Total $ 0.3 $ 0.3 $ —
Assumptions used to calculate net periodic cost and benefit obligations.	The assumptions used to calculate the benefit obligations are as follows: 2017 2016 Weighted average discount rate - Spire Missouri East plans 3.75% 3.50% Weighted average discount rate - Spire Missouri West plans 3.70% 3.50% Weighted average discount rate - Spire Alabama plans 3.65%/3.70% 3.45%/3.50% Weighted average rate of future compensation increase 3.00% 3.00% The assumptions used to calculate net periodic pension costs for Spire Missouri are as follows: 2017 2016 2015 Weighted average discount rate - Spire Missouri East plans 3.50% 4.40% 4.30% Weighted average discount rate - Spire Missouri West plans 3.50% 4.50% 4.45% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 7.75% 7.75% 7.75% The assumptions used to calculate net periodic pension costs for Spire Alabama are as follows: 2017 2016 2015 Weighted average discount rate 3.45%/3.50% 4.25%/4.30% 4.15%/4.25% Weighted average rate of future compensation increase 3.00% 3.00% 2.92% Expected long-term rate of return on plan assets 7.25% 7.50% 7.00%/7.25%
Projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for plans that have projected benefit obligation and accumulated benefit obligation in excess of plan assets	Following are the year-end projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for plans that have a projected benefit obligation and an accumulated benefit obligation in excess of plan assets: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Projected benefit obligation $ 748.8 $ 794.7 $ 539.6 $ 560.0 $ 148.2 $ 174.3 Accumulated benefit obligation 701.4 724.5 500.4 517.7 142.8 149.8 Fair value of plan assets 531.6 540.5 385.9 395.7 97.9 100.0
Targeted and actual plan assets by category	Following are the targeted and actual plan assets by category as of September 30 of each year for Spire Missouri and Spire Alabama: Spire Missouri 2017 2017 2016 2016 Equity markets 56.4 % 56.8 % 56.2 % 56.9 % Debt securities 43.6 % 42.0 % 43.8 % 43.1 % Cash equivalents — % 1.2 % — % — % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Alabama 2017 2017 2016 2016 Equity markets 60.0 % 58.5 % 60.0 % 59.2 % Debt securities 29.0 % 28.7 % 29.0 % 28.8 % Other* 11.0 % 12.8 % 11.0 % 12.0 % Total 100.0 % 100.0 % 100.0 % 100.0 % * Includes cash and funds invested in real estate, commodities, natural resources and inflation-protected securities.
Expected benefit payments for the succeeding five fiscal years	Following are expected pension benefit payments for the succeeding five fiscal years, and in aggregate for the five fiscal years thereafter, for Spire, Spire Missouri, and Spire Alabama: 2018 2019 2020 2021 2022 2023- 2027 Spire $ 63.5 $ 63.2 $ 63.2 $ 58.1 $ 57.9 $ 281.1 Spire Missouri 50.7 49.5 49.1 43.5 42.1 198.1 Spire Alabama 10.3 11.1 11.5 11.9 13.0 67.8
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic cost	Net periodic postretirement benefit costs consist of the following components: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Service cost – benefits earned during the period $ 11.0 $ 10.9 $ 12.8 $ 10.4 $ 10.6 $ 12.3 $ 0.3 $ 0.3 $ 0.5 Interest cost on accumulated postretirement benefit obligation 8.6 10.2 11.2 6.8 8.1 8.6 1.6 2.1 2.6 Expected return on plan assets (13.6 ) (13.5 ) (13.2 ) (9.0 ) (8.5 ) (8.1 ) (4.4 ) (5.0 ) (5.1 ) Amortization of prior service cost (credit) — 0.3 0.8 0.2 0.3 0.8 (0.2 ) — — Amortization of actuarial loss (gain) 2.5 3.6 5.1 2.6 3.8 5.1 (0.1 ) (0.2 ) — Special termination benefits — 2.6 — — 2.6 — — — — Subtotal 8.5 14.1 16.7 11.0 16.9 18.7 (2.8 ) (2.8 ) (2.0 ) Regulatory adjustment (3.2 ) (6.6 ) (11.0 ) (1.5 ) (4.8 ) (9.2 ) (1.8 ) (1.8 ) (1.8 ) Net postretirement benefit cost $ 5.3 $ 7.5 $ 5.7 $ 9.5 $ 12.1 $ 9.5 $ (4.6 ) $ (4.6 ) $ (3.8 )
Other changes in plan assets and benefit obligations recognized in other comprehensive income	Other changes in plan assets and postretirement benefit obligations recognized in OCI include the following: Spire Spire Missouri Spire Alabama 2017 2016 2015 2017 2016 2015 2017 2016 2015 Current year actuarial (gain) loss $ (34.1 ) $ 0.8 $ (8.5 ) $ (28.5 ) $ 1.4 $ (2.4 ) $ (4.5 ) $ (0.6 ) $ (6.1 ) Amortization of actuarial (loss) gain (2.5 ) (3.6 ) (5.1 ) (2.6 ) (3.8 ) (5.1 ) 0.1 0.2 — Current year prior service credit (1.4 ) (1.8 ) (4.9 ) — — (4.9 ) (1.4 ) (1.8 ) — Amortization of prior service (cost) credit — (0.3 ) (0.8 ) (0.2 ) (0.3 ) (0.8 ) 0.2 — — Subtotal (38.0 ) (4.9 ) (19.3 ) (31.3 ) (2.7 ) (13.2 ) (5.6 ) (2.2 ) (6.1 ) Regulatory adjustment 38.0 4.9 19.3 31.3 2.7 13.2 5.6 2.2 6.1 Total recognized in OCI $ — $ — $ — $ — $ — $ — $ — $ — $ —
Reconciliation of the beginning and ending balances of benefit obligation	The following table sets forth the reconciliation of the beginning and ending balances of the postretirement benefit obligation at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Benefit obligation, beginning of year $ 259.2 $ 239.2 $ 207.9 $ 191.9 $ 45.4 $ 47.3 Service cost 11.0 10.9 10.4 10.6 0.3 0.3 Interest cost 8.6 10.2 6.8 8.1 1.6 2.1 Actuarial (gain) loss (22.1 ) 7.1 (20.9 ) 6.7 — 0.4 Plan amendments (1.4 ) (1.8 ) — — (1.4 ) (1.8 ) Spire EnergySouth acquisition — 5.9 — — — — Special termination benefits — 2.6 — 2.6 — — Curtailments 0.4 — — — — — Retiree drug subsidy program 0.3 0.2 0.3 — — 0.2 Gross benefits paid (17.5 ) (15.1 ) (12.0 ) (12.0 ) (5.3 ) (3.1 ) Benefit obligation, end of year $ 238.5 $ 259.2 $ 192.5 $ 207.9 $ 40.6 $ 45.4
Fair value of plan assets	The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Fair value of plan assets at beginning of year $ 246.4 $ 223.3 $ 159.7 $ 143.6 $ 82.8 $ 79.7 Actual return on plan assets 26.2 19.9 16.8 13.8 8.9 6.2 Employer contributions 10.4 14.3 10.4 14.3 — — Spire EnergySouth acquisition — 4.0 — — — — Gross benefits paid (17.5 ) (15.1 ) (12.0 ) (12.0 ) (5.3 ) (3.1 ) Fair value of plan assets, end of year $ 265.5 $ 246.4 $ 174.9 $ 159.7 $ 86.4 $ 82.8 Funded status of plans, end of year $ 27.0 $ (12.8 ) $ (17.6 ) $ (48.2 ) $ 45.8 $ 37.4
Amounts recognized in consolidated balance sheets	The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Current assets $ 1.4 $ 0.3 $ 1.4 $ 0.3 $ — $ — Noncurrent assets 47.0 37.4 1.2 — 45.8 37.4 Current liabilities (0.4 ) (0.4 ) (0.4 ) (0.4 ) — — Noncurrent liabilities (21.0 ) (50.1 ) (19.8 ) (48.1 ) — — Total $ 27.0 $ (12.8 ) $ (17.6 ) $ (48.2 ) $ 45.8 $ 37.4 Pre-tax amounts recognized in accumulated other comprehensive loss not yet recognized as components of net periodic postretirement benefit cost consist of: Spire Spire Missouri Spire Alabama 2017 2016 2017 2016 2017 2016 Net actuarial loss (gain) $ 1.5 $ 38.0 $ 12.3 $ 43.4 $ (9.7 ) $ (5.4 ) Prior service credit (6.6 ) (5.2 ) (3.7 ) (3.4 ) (2.9 ) (1.8 ) Subtotal (5.1 ) 32.8 8.6 40.0 (12.6 ) (7.2 ) Adjustments for amounts included in regulatory assets 5.1 (32.8 ) (8.6 ) (40.0 ) 12.6 7.2 Total $ — $ — $ — $ — $ — $ —
Pre-tax amounts amortized from accumulated other comprehensive income into net periodic cost	At September 30, 2017 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic postretirement benefit cost during fiscal 2018: Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ 0.9 $ 0.9 $ — Amortization of prior service (credit) cost (0.1 ) 0.3 (0.4 ) Subtotal 0.8 1.2 (0.4 ) Regulatory adjustment (0.8 ) (1.2 ) 0.4 Total $ — $ — $ —
Assumptions used to calculate net periodic cost and benefit obligations.	The assumptions used to calculate net periodic postretirement benefit costs for Spire Missouri are as follows: 2017 2016 2015 Weighted average discount rate - Spire Missouri East plans 3.15% 4.00% 4.15% Weighted average discount rate - Spire Missouri West plans 3.45% 4.30% 4.40% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets - Spire Missouri East plans 5.75%/7.75% 6.00%/7.75% 6.25%/7.75% Expected long-term rate of return on plan assets - Spire Missouri West plans 5.50% 4.75% 5.00% The assumptions used to calculate net periodic postretirement benefit costs for Spire Alabama are as follows: 2017 2016 2015 Weighted average discount rate 3.60% 4.50% 4.40% Expected long-term rate of return on plan assets 4.00%/6.25% 4.50%/7.25% 4.75%/7.50% The assumptions used to calculate the accumulated postretirement benefit obligations are as follows: 2017 2016 Weighted average discount rate - Spire Alabama plans 3.80% 3.60% Weighted average discount rate - Spire Missouri East plans 3.60% 3.15% Weighted average discount rate - Spire Missouri West plans 3.60% 3.45% Weighted average rate of future compensation increase - Spire Missouri East plans 3.00% 3.00%
Targeted and actual plan assets by category	Following are the targeted and actual plan assets by category as of September 30 of each year for Spire Missouri and Spire Alabama: Spire Missouri Target 2017 Actual 2016 Actual Equity securities 60.0 % 59.0 % 59.1 % Debt securities 40.0 % 39.4 % 39.4 % Other (cash and cash equivalents held to make benefit payments) — % 1.6 % 1.5 % Total 100.0 % 100.0 % 100.0 % Spire Alabama Target 2017 Actual 2016 Actual Equity securities 60.0 % 60.1 % 60.5 % Debt securities 40.0 % 39.9 % 39.5 % Total 100.0 % 100.0 % 100.0 %
Expected benefit payments for the succeeding five fiscal years	Following are expected postretirement benefit payments for the succeeding five fiscal years, and in aggregate for the five fiscal years thereafter for Spire, Spire Missouri, and Spire Alabama: 2018 2019 2020 2021 2022 2023- 2027 Spire $ 15.0 $ 16.0 $ 17.1 $ 18.3 $ 18.9 $ 101.3 Spire Missouri 11.8 12.8 14.0 15.2 15.9 86.5 Spire Alabama 2.8 2.8 2.8 2.8 2.7 13.0
Assumed medical cost trend rates and effect of an assumed 1% changed in assumed medical cost trend.	The assumed medical cost trend rates at September 30 are as follows: 2017 2016 Medical cost trend assumed for next year - Spire Missouri 7.25% 7.50% Medical cost trend assumed for next year - Spire Alabama 7.25% 7.50% Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate) 5.00% 5.00% Year the rate reaches the ultimate trend 2023 2023 The following table presents the effects of an assumed 1% change in the assumed medical cost trend rate: Spire Spire Missouri Spire Alabama 1% Increase 1% Decrease 1% Increase 1% Decrease 1% Increase 1% Decrease Net periodic postretirement benefit cost $ 1.7 $ (1.4 ) $ 1.6 $ (1.3 ) $ 0.1 $ (0.1 ) Accumulated postretirement benefit obligation 10.0 (9.2 ) 8.0 (7.4 ) 1.4 (1.3 )
Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	The table below categorizes the fair value measurements of Spire Alabama’s pension plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 3.4 $ — $ — $ 3.4 Equity mutual funds - domestic 28.4 9.1 — 37.5 Equity mutual funds - international 25.2 3.7 — 28.9 Debt securities: US bond mutual funds 23.2 — — 23.2 International — 4.9 — 4.9 Total $ 80.2 $ 17.7 $ — $ 97.9 As of September 30, 2016 Cash and cash equivalents $ 0.4 $ — $ — $ 0.4 Stock/bond mutual funds 59.0 11.9 — 70.9 Debt securities: US bond mutual funds 23.0 5.7 — 28.7 Total $ 82.4 $ 17.6 $ — $ 100.0 The table below categorizes the fair value measurements of Spire Alabama’s postretirement plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 US stock/bond mutual funds $ — $ 71.7 $ — $ 71.7 International fund — 14.7 — 14.7 Total $ — $ 86.4 $ — $ 86.4 As of September 30, 2016 US stock/bond mutual funds $ — $ 68.5 $ — $ 68.5 International fund — 14.3 — 14.3 Total $ — $ 82.8 $ — $ 82.8 The table below categorizes the fair value measurements of Spire Missouri’s pension plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 31.7 $ — $ — $ 31.7 Equity mutual funds - domestic — 11.9 — 11.9 Equity mutual funds - international — 5.7 — 5.7 Debt securities: US bond mutual funds — 68.5 — 68.5 US government 33.2 4.5 — 37.7 US corporate 183.7 — — 183.7 US municipal 4.2 — — 4.2 International 45.1 — — 45.1 Derivatives and margin (payable) (2.6 ) — — (2.6 ) Total $ 295.3 $ 90.6 $ — $ 385.9 As of September 30, 2016 Cash and cash equivalents $ 46.5 $ — $ — $ 46.5 Stock/bond mutual funds — 14.8 0.1 14.9 Debt securities: US bond mutual funds — 120.2 — 120.2 US government 42.1 3.0 — 45.1 US corporate 137.4 — — 137.4 US municipal 6.3 — — 6.3 International 25.2 — — 25.2 Derivatives and margin (payable) (1.0 ) 1.1 — 0.1 Total $ 256.5 $ 139.1 $ 0.1 $ 395.7 The table below categorizes the fair value measurements of Spire Missouri’s postretirement plan assets: Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total As of September 30, 2017 Cash and cash equivalents $ 3.9 $ — $ — $ 3.9 US stock/bond mutual funds 171.0 — — 171.0 Total $ 174.9 $ — $ — $ 174.9 As of September 30, 2016 Cash and cash equivalents $ 4.6 $ — $ — $ 4.6 US stock/bond mutual funds 155.1 — — 155.1 Total $ 159.7 $ — $ — $ 159.7

INFORMATION BY OPERATING SEGM42

INFORMATION BY OPERATING SEGMENT (Tables)	12 Months Ended
INFORMATION BY OPERATING SEGMENT (Tables)	Sep. 30, 2017
Segment Reporting [Abstract]
Schedule of operating segment information	Gas Utility Gas Marketing Other Eliminations Consolidated 2017 Revenues from external customers $ 1,660.0 $ 79.3 $ 1.4 $ — $ 1,740.7 Intersegment revenues 7.9 — 6.3 (14.2 ) — Total Operating Revenues 1,667.9 79.3 7.7 (14.2 ) 1,740.7 Operating Expenses Gas Utility Natural and propane gas 645.9 — — (75.4 ) 570.5 Other operation and maintenance 409.1 — — (4.1 ) 405.0 Depreciation and amortization 153.5 — — — 153.5 Taxes, other than income taxes 137.8 — — — 137.8 Total Gas Utility Operating Expenses 1,346.3 — — (79.5 ) 1,266.8 Gas Marketing and Other * — 74.1 12.8 65.3 152.2 Total Operating Expenses 1,346.3 74.1 12.8 (14.2 ) 1,419.0 Operating Income (Loss) $ 321.6 $ 5.2 $ (5.1 ) $ — $ 321.7 Net Economic Earnings (Loss) $ 181.5 $ 6.8 $ (20.7 ) $ — $ 167.6 Capital Expenditures $ 412.6 $ — $ 25.5 $ — $ 438.1 Gas Utility Gas Marketing Other Eliminations Consolidated 2016 Revenues from external customers $ 1,457.2 $ 78.5 $ 1.6 $ — $ 1,537.3 Intersegment revenues 2.2 — 3.2 (5.4 ) — Total Operating Revenues 1,459.4 78.5 4.8 (5.4 ) 1,537.3 Operating Expenses Gas Utility Natural and propane gas 539.7 — — (47.5 ) 492.2 Other operation and maintenance 379.3 — — (1.8 ) 377.5 Depreciation and amortization 136.9 — — — 136.9 Taxes, other than income taxes 125.2 — — — 125.2 Total Gas Utility Operating Expenses 1,181.1 — — (49.3 ) 1,131.8 Gas Marketing and Other * — 66.7 12.6 43.9 123.2 Total Operating Expenses 1,181.1 66.7 12.6 (5.4 ) 1,255.0 Operating Income (Loss) $ 278.3 $ 11.8 $ (7.8 ) $ — $ 282.3 Net Economic Earnings (Loss) $ 160.3 $ 6.4 $ (17.6 ) $ — $ 149.1 Capital Expenditures $ 291.7 $ — $ 1.6 $ — $ 293.3 Gas Utility Gas Marketing Other Eliminations Consolidated 2015 Revenues from external customers $ 1,891.8 $ 82.9 $ 1.7 $ — $ 1,976.4 Intersegment revenues 4.0 70.5 2.0 (76.5 ) — Total Operating Revenues 1,895.8 153.4 3.7 (76.5 ) 1,976.4 Operating Expenses Gas Utility Natural and propane gas 957.6 — — (75.2 ) 882.4 Other operation and maintenance 391.6 — — (1.0 ) 390.6 Depreciation and amortization 129.9 — — — 129.9 Taxes, other than income taxes 142.1 — — — 142.1 Total Gas Utility Operating Expenses 1,621.2 — — (76.2 ) 1,545.0 Gas Marketing and Other * — 146.6 12.6 (0.3 ) 158.9 Total Operating Expenses 1,621.2 146.6 12.6 (76.5 ) 1,703.9 Operating Income (Loss) $ 274.6 $ 6.8 $ (8.9 ) $ — $ 272.5 Net Economic Earnings (Loss) $ 150.4 $ 4.2 $ (16.3 ) $ — $ 138.3 Capital Expenditures $ 284.4 $ — $ 5.4 $ — $ 289.8 * Operating Expenses for “Gas Marketing and Other” include depreciation and amortization for Gas Marketing ( $0.1 for 2017 , $0.1 for 2016 , and $0.3 for 2015 ) and for Other ( $0.5 for 2017 , $0.5 for 2016 , and $0.6 for 2015 ). Total Assets at End of Year 2017 2016 2015 Gas Utility $ 5,551.2 $ 5,184.7 $ 4,679.3 Gas Marketing 246.2 205.0 160.6 Other 2,239.5 1,836.6 1,554.5 Eliminations (1,490.2 ) (1,161.9 ) (1,116.8 ) Total Assets $ 6,546.7 $ 6,064.4 $ 5,277.6
Schedule of the reconciliation of consolidated net economic earnings to consolidated net income	Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings 2017 2016 2015 Net Income $ 161.6 $ 144.2 $ 136.9 Adjustments, pre-tax: Unrealized loss (gain) on energy-related derivatives 6.0 (0.1 ) (2.8 ) Lower of cost or market inventory adjustments — 0.2 0.4 Realized (gain) loss on economic hedges prior to the sale of the physical commodity (0.3 ) (1.6 ) 2.4 Acquisition, divestiture and restructuring activities 4.0 9.2 9.8 Gain on sale of property — — (7.6 ) Income tax effect of adjustments (3.7 ) (2.8 ) (0.8 ) Net Economic Earnings $ 167.6 $ 149.1 $ 138.3

REGULATORY MATTERS (Tables)

REGULATORY MATTERS (Tables)	12 Months Ended
REGULATORY MATTERS (Tables)	Sep. 30, 2017
Regulated Operations [Abstract]
Schedule of regulatory assets	The following regulatory assets and regulatory liabilities were reflected in the Balance Sheets as of September 30, 2017 and 2016 . Unamortized Purchased Gas Adjustments are also included below, which are reported separately in the current assets and liabilities sections of each balance sheet. Spire Spire Missouri Spire Alabama September 30 2017 2016 2017 2016 2017 2016 Regulatory Assets: Current: Pension and postretirement benefit costs $ 42.2 $ 27.0 $ 34.9 $ 20.2 $ 7.2 $ 6.8 Unamortized purchased gas adjustments 102.6 49.7 57.4 43.1 45.2 5.6 Other 30.7 17.2 3.3 3.7 12.2 8.1 Total Current Regulatory Assets 175.5 93.9 95.6 67.0 64.6 20.5 Noncurrent: Future income taxes due from customers 170.5 151.3 170.5 151.3 — — Pension and postretirement benefit costs 404.7 487.9 322.7 375.7 72.6 98.9 Cost of removal 123.3 130.6 — — 123.3 130.6 Unamortized purchased gas adjustments 9.9 12.6 9.9 12.6 — — Energy efficiency 29.0 25.5 29.0 25.5 — — Other 53.7 30.1 25.7 24.7 1.1 1.2 Total Noncurrent Regulatory Assets 791.1 838.0 557.8 589.8 197.0 230.7 Total Regulatory Assets $ 966.6 $ 931.9 $ 653.4 $ 656.8 $ 261.6 $ 251.2 Regulatory Liabilities: Current: RSE adjustment $ 1.4 $ 7.5 $ — $ — $ 1.4 $ 5.0 Unbilled service margin — 5.9 — — — 5.9 Refundable negative salvage 8.2 9.3 — — 8.2 9.3 Unamortized purchased gas adjustments 1.0 1.7 — — — — Other 12.0 6.2 2.7 1.3 2.4 2.5 Total Current Regulatory Liabilities 22.6 30.6 2.7 1.3 12.0 22.7 Noncurrent: Pension and postretirement benefit costs 32.2 28.9 — — 32.2 28.9 Refundable negative salvage 4.1 9.4 — — 4.1 9.4 Accrued cost of removal 83.8 74.8 54.5 55.1 — — Other 37.1 17.6 26.7 12.2 3.3 3.4 Total Noncurrent Regulatory Liabilities 157.2 130.7 81.2 67.3 39.6 41.7 Total Regulatory Liabilities $ 179.8 $ 161.3 $ 83.9 $ 68.6 $ 51.6 $ 64.4 A portion of the Company’s regulatory assets are not earning a return and are shown in the schedule below: Spire Spire Missouri September 30 2017 2016 2017 2016 Future income taxes due from customers $ 170.5 $ 151.3 $ 170.5 $ 151.3 Pension and postretirement benefit costs 198.5 240.6 198.5 240.6 Other 11.3 12.9 11.3 12.9 Total Regulatory Assets Not Earning a Return $ 380.3 $ 404.8 $ 380.3 $ 404.8
Schedule of regulatory liabilities	The following regulatory assets and regulatory liabilities were reflected in the Balance Sheets as of September 30, 2017 and 2016 . Unamortized Purchased Gas Adjustments are also included below, which are reported separately in the current assets and liabilities sections of each balance sheet. Spire Spire Missouri Spire Alabama September 30 2017 2016 2017 2016 2017 2016 Regulatory Assets: Current: Pension and postretirement benefit costs $ 42.2 $ 27.0 $ 34.9 $ 20.2 $ 7.2 $ 6.8 Unamortized purchased gas adjustments 102.6 49.7 57.4 43.1 45.2 5.6 Other 30.7 17.2 3.3 3.7 12.2 8.1 Total Current Regulatory Assets 175.5 93.9 95.6 67.0 64.6 20.5 Noncurrent: Future income taxes due from customers 170.5 151.3 170.5 151.3 — — Pension and postretirement benefit costs 404.7 487.9 322.7 375.7 72.6 98.9 Cost of removal 123.3 130.6 — — 123.3 130.6 Unamortized purchased gas adjustments 9.9 12.6 9.9 12.6 — — Energy efficiency 29.0 25.5 29.0 25.5 — — Other 53.7 30.1 25.7 24.7 1.1 1.2 Total Noncurrent Regulatory Assets 791.1 838.0 557.8 589.8 197.0 230.7 Total Regulatory Assets $ 966.6 $ 931.9 $ 653.4 $ 656.8 $ 261.6 $ 251.2 Regulatory Liabilities: Current: RSE adjustment $ 1.4 $ 7.5 $ — $ — $ 1.4 $ 5.0 Unbilled service margin — 5.9 — — — 5.9 Refundable negative salvage 8.2 9.3 — — 8.2 9.3 Unamortized purchased gas adjustments 1.0 1.7 — — — — Other 12.0 6.2 2.7 1.3 2.4 2.5 Total Current Regulatory Liabilities 22.6 30.6 2.7 1.3 12.0 22.7 Noncurrent: Pension and postretirement benefit costs 32.2 28.9 — — 32.2 28.9 Refundable negative salvage 4.1 9.4 — — 4.1 9.4 Accrued cost of removal 83.8 74.8 54.5 55.1 — — Other 37.1 17.6 26.7 12.2 3.3 3.4 Total Noncurrent Regulatory Liabilities 157.2 130.7 81.2 67.3 39.6 41.7 Total Regulatory Liabilities $ 179.8 $ 161.3 $ 83.9 $ 68.6 $ 51.6 $ 64.4

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Tables)	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Aggregate Rental Expense and Annual Minimum Rental Commitments	Aggregate rental expense and annual minimum rental commitments under all leases having an initial or remaining non-cancelable term of more than one year are shown below: Aggregate Rental Expense Minimum Rental Commitments 2017 2016 2015 2018 2019 2020 2021 2022 Later Total Spire $ 9.7 $ 11.9 $ 14.1 $ 10.1 $ 9.3 $ 7.8 $ 6.1 $ 6.0 $ 44.4 $ 83.7 Spire Missouri 4.8 4.3 7.6 2.1 1.3 0.2 0.2 — — 3.8 Spire Alabama 4.6 3.7 4.0 4.0 4.1 3.8 2.1 2.1 2.8 18.9

INTERIM FINANCIAL INFORMATION45

INTERIM FINANCIAL INFORMATION (UNAUDITED) (Tables)	12 Months Ended
INTERIM FINANCIAL INFORMATION (UNAUDITED) (Tables)	Sep. 30, 2017
Quarterly Financial Information [Line Items]
Schedule of Quarterly Financial Information	Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2017 Total Operating Revenues $ 495.1 $ 663.4 $ 323.5 $ 258.7 Operating Income 89.1 180.4 50.3 1.9 Net Income (Loss) 45.2 108.0 21.7 (13.3 ) Basic Earnings (Loss) Per Share of Common Stock $ 0.99 $ 2.36 $ 0.45 $ (0.28 ) Diluted Earnings (Loss) Per Share of Common Stock $ 0.99 $ 2.36 $ 0.45 $ (0.28 ) Fiscal Year 2016 Total Operating Revenues $ 399.4 $ 609.3 $ 249.3 $ 279.3 Operating Income (Loss) 87.0 167.7 35.3 (7.7 ) Net Income (Loss) 46.9 100.8 10.7 (14.2 ) Basic Earnings (Loss) Per Share of Common Stock $ 1.08 $ 2.32 $ 0.24 $ (0.31 ) Diluted Earnings (Loss) Per Share of Common Stock $ 1.08 $ 2.31 $ 0.24 $ (0.31 )
Spire Missouri
Quarterly Financial Information [Line Items]
Schedule of Quarterly Financial Information	Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2017 Total Operating Revenues $ 363.6 $ 447.2 $ 198.5 $ 162.6 Operating Income 64.5 90.2 30.5 11.7 Net Income 38.0 57.0 15.5 2.5 Fiscal Year 2016 Total Operating Revenues $ 317.2 $ 446.7 $ 179.3 $ 144.3 Operating Income 65.1 87.0 29.4 5.4 Net Income (Loss) 39.4 54.3 13.9 (1.7 )
Spire Alabama
Quarterly Financial Information [Line Items]
Schedule of Quarterly Financial Information	Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2017 Total Operating Revenues $ 86.7 $ 158.8 $ 90.5 $ 64.5 Operating Income (Loss) 19.8 78.9 15.5 (8.4 ) Net Income (Loss) 10.3 47.6 7.4 (7.2 ) Fiscal Year 2016 Total Operating Revenues $ 82.3 $ 166.0 $ 74.0 $ 46.2 Operating Income (Loss) 18.9 80.4 9.3 (17.1 ) Net Income (Loss) 9.9 48.1 4.0 (8.8 )

SUMMARY OF SIGNIFICANT ACCOUN46

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	12 Months Ended
	Sep. 30, 2017USD ($)operating_segmentchange	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
Related Party Transaction [Line Items]
Number of operating segments \| operating_segment	2
Utility Plant, Depreciation and Amortization [Abstract]
Accruals for capital expenditures	$ 41,000,000	$ 30,400,000	$ 13,400,000
Amount by which the replacement cost exceeds (less than) the cost basis value of stored gas inventories	$ 20,800,000	11,400,000
Number of months of the original maturity of debt instruments purchased	3 months
Finance receivable, net	$ 12,500,000	11,800,000
Retrospective Effect is ASU had been Adopted \| ASU 2015-03 \| New Accounting Pronouncement, Early Adoption, Effect \| Long-Term Debt
Utility Plant, Depreciation and Amortization [Abstract]
Deferred finance costs	$ 13,200,000	$ 13,000,000
Spire Missouri
Utility Plant, Depreciation and Amortization [Abstract]
Average annual depreciation and amortization expense percentage	3.00%	3.00%	3.00%
Accruals for capital expenditures	$ 28,900,000	$ 14,800,000	$ 9,600,000
Number of PGA discretionary changes \| change	3
Months between PGA discretionary changes	2 months
Cost savings retention percentage	10.00%
Maximum amount of cost savings allowable	$ 3,000,000
Accrued unbilled revenues	30,100,000	26,100,000
Spire Missouri \| Retrospective Effect is ASU had been Adopted \| ASU 2015-03 \| New Accounting Pronouncement, Early Adoption, Effect \| Long-Term Debt
Utility Plant, Depreciation and Amortization [Abstract]
Deferred finance costs	4,200,000	4,800,000
Spire Alabama
Utility Plant, Depreciation and Amortization [Abstract]
Accruals for capital expenditures	$ 9,400,000	6,800,000	$ 3,100,000
Composite depreciation rate	3.10%
Accrued unbilled revenues	$ 0	5,900,000
Threshold period past due for collection	90 days
Threshold period past due for write-off of financing receivable	12 months
Write off on an allowance for credit losses	$ 400,000	400,000
Spire Alabama \| Retrospective Effect is ASU had been Adopted \| ASU 2015-03 \| New Accounting Pronouncement, Early Adoption, Effect \| Long-Term Debt
Utility Plant, Depreciation and Amortization [Abstract]
Deferred finance costs	2,600,000	2,400,000
Spire Alabama \| Financing Receivables, Equal to Greater than 90 Days Past Due
Utility Plant, Depreciation and Amortization [Abstract]
Finance receivable 90 days past due	$ 400,000	$ 400,000

SUMMARY OF SIGNIFICANT ACCOUN47

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Asset retirement obligations [Roll forward]
Asset retirement obligations, beginning of year	$ 206.4	$ 159.2
Liabilities incurred during the period	5.5	4.1
Liabilities settled during the period	(4.6)	(9.5)
Accretion	9.1	13.2
Revisions in estimated cash flows	80.2	27.5
Asset retirement obligations, end of year	296.6	206.4
Spire Missouri
Asset retirement obligations [Roll forward]
Asset retirement obligations, beginning of year	75.2	72.4
Liabilities incurred during the period	0.3	1.2
Liabilities settled during the period	(1.1)	(1.9)
Accretion	3.6	3.5
Revisions in estimated cash flows	80.6	0
Asset retirement obligations, end of year	158.6	75.2
Spire Alabama
Asset retirement obligations [Roll forward]
Asset retirement obligations, beginning of year	120.1	86.6
Liabilities incurred during the period	5.2	2.9
Liabilities settled during the period	(1.9)	(6.8)
Accretion	5	9.7
Revisions in estimated cash flows	0	27.7
Asset retirement obligations, end of year	128.4	120.1
EnergySouth
Asset retirement obligations [Roll forward]
Addition of Spire EnergySouth asset retirement obligations	0	11.9
EnergySouth \| Spire Missouri
Asset retirement obligations [Roll forward]
Addition of Spire EnergySouth asset retirement obligations	0	0
EnergySouth \| Spire Alabama
Asset retirement obligations [Roll forward]
Addition of Spire EnergySouth asset retirement obligations	$ 0	$ 0

SUMMARY OF SIGNIFICANT ACCOUN48

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Off System Sales (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017USD ($)
Spire Missouri East \| First $2.0 of pre-tax income
Off System Sales [Line Items]
Pre-tax Income	$ 2
Customer Share	85.00%
Company Share	15.00%
Spire Missouri East \| Next $2.0 of pre-tax income
Off System Sales [Line Items]
Pre-tax Income	$ 2
Customer Share	80.00%
Company Share	20.00%
Spire Missouri East \| Next $2.0 of pre-tax income
Off System Sales [Line Items]
Pre-tax Income	$ 2
Customer Share	75.00%
Company Share	25.00%
Spire Missouri East \| Amounts of pre-tax income exceeding $6.0
Off System Sales [Line Items]
Pre-tax Income	$ 6
Customer Share	70.00%
Company Share	30.00%
Spire Missouri West \| First $1.2 of pre-tax income
Off System Sales [Line Items]
Pre-tax Income	$ 1.2
Customer Share	85.00%
Company Share	15.00%
Spire Missouri West \| Next $1.2 of pre-tax income
Off System Sales [Line Items]
Pre-tax Income	$ 1.2
Customer Share	80.00%
Company Share	20.00%
Spire Missouri West \| Next $1.2 of pre-tax income
Off System Sales [Line Items]
Pre-tax Income	$ 1.2
Customer Share	75.00%
Company Share	25.00%
Spire Missouri West \| Amounts of pre-tax income exceeding $3.6
Off System Sales [Line Items]
Pre-tax Income	$ 3.6
Customer Share	70.00%
Company Share	30.00%

SUMMARY OF SIGNIFICANT ACCOUN49

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Goodwill [Line Items]
Accruals for capital expenditures	$ 41	$ 30.4	$ 13.4
Goodwill [Roll Forward]
Beginning balance	1,164.9	946	937.8
Goodwill	6.7		8.2
Acquisition		218.9
Ending balance	1,171.6	1,164.9	946
Operating Segments \| Gas Utility:
Goodwill [Roll Forward]
Beginning balance	210.2	210.2	210.2
Goodwill	0		0
Acquisition		0
Ending balance	210.2	210.2	210.2
Operating Segments \| Gas Marketing:
Goodwill [Roll Forward]
Beginning balance	0	0	0
Goodwill	0		0
Acquisition		0
Ending balance	0	0	0
Other
Goodwill [Roll Forward]
Beginning balance	954.7	735.8	727.6
Goodwill	6.7		8.2
Acquisition		218.9
Ending balance	961.4	954.7	735.8
Spire Missouri
Goodwill [Line Items]
Accruals for capital expenditures	28.9	14.8	$ 9.6
Goodwill [Roll Forward]
Beginning balance	210.2
Ending balance	$ 210.2	$ 210.2

SUMMARY OF SIGNIFICANT ACCOUN50

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Gross Receipts and Sales Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Schedule of Gross Receipts Taxes [Line Items]
Gross Receipts taxes recorded in regulated gas distribution operating revenues	$ 84.6	$ 75.5	$ 97.3
Spire Missouri
Schedule of Gross Receipts Taxes [Line Items]
Gross Receipts taxes recorded in regulated gas distribution operating revenues	60.7	57.4	74.5
Spire Alabama
Schedule of Gross Receipts Taxes [Line Items]
Gross Receipts taxes recorded in regulated gas distribution operating revenues	$ 19.5	$ 17.9	$ 22.6

SUMMARY OF SIGNIFICANT ACCOUN51

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Transactions with Affiliates (Details) - Affiliated Entity - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Laclede Pipeline Company [Member] \| Unregulated Operation \| Spire Missouri
Related Party Transaction [Line Items]
Revenue from related parties	$ 1	$ 1
Spire Missouri \| Regulated Operation \| Spire marketing
Related Party Transaction [Line Items]
Revenue from related parties	7.8	1.9	$ 4
Spire marketing \| Regulated Operation \| Spire Missouri
Related Party Transaction [Line Items]
Revenue from related parties	$ 74.4	$ 46.3	$ 74.1

ACQUISITIONS - Narrative (Detai

ACQUISITIONS - Narrative (Details) - USD ($) $ in Millions	Sep. 12, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 12, 2017	Sep. 30, 2014
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired		$ 3.8	$ (317.7)	$ 0
Goodwill		1,171.6	$ 1,164.9	$ 946		$ 937.8
EnergySouth
Business Acquisition [Line Items]
Percentage of voting interest acquired	100.00%
Payments to acquire businesses, net of cash acquired	$ (313.9)
Goodwill	$ 218.9	$ 225.6			$ 225.6

ACQUISITIONS - Summary of Consi

ACQUISITIONS - Summary of Consideration Paid, Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 12, 2016	Sep. 30, 2017	Sep. 30, 2015	Sep. 12, 2017	Sep. 30, 2016	Sep. 30, 2014
Business Acquisition [Line Items]
Goodwill	$ 1,171.6		$ 1,171.6	$ 946		$ 1,164.9	$ 937.8
Measurement period adjustments
Goodwill			6.7	$ 8.2
EnergySouth
Business Acquisition [Line Items]
Utility plant	199.5	$ 199.5	199.5
Cash	2	2	2
Other current assets	17.7	17.5	17.7
Other assets	69.1	79.8	69.1
Long-term debt	(67)	(67)	(67)
Other current liabilities	(42.7)	(42.7)	(42.7)
Deferred tax liabilities	(35.5)	(35.5)	(35.5)
Other liabilities	(52.8)	(52.8)	(52.8)
Total identifiable net assets	90.3	100.8	90.3
Goodwill	225.6	218.9	$ 225.6		$ 225.6
Measurement period adjustments
Other current assets		0.2
Other assets		(10.7)
Total identifiable net assets		(10.5)
Goodwill		6.7
Consideration (cash)		(3.8)
Consideration (cash)	$ 315.9	$ 319.7

ACQUISITIONS - Pro Forma Inform

ACQUISITIONS - Pro Forma Information, Revenues and Earnings (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Alagasco and EnergySouth
Business Acquisition [Line Items]
Total Operating Revenues	$ 1,740.7	$ 1,632.4	$ 2,081.6
Net Income	$ 161.6	$ 153.9	$ 143.6
Basic earnings (loss) per share (in dollars per share)	$ 3.44	$ 3.48	$ 3.32
Diluted earnings (loss) per share (in dollars per share)	$ 3.43	$ 3.46	$ 3.31
EnergySouth
Business Acquisition [Line Items]
Pro forma, Total Operating Revenues	$ 95.5	$ 3.3
Pro forma, Net Income (Loss)	$ 9.4	$ (0.2)
Pro forma, Earnings (Loss) Per Share (in dollars per share)	$ 0.20	$ 0

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period, minimum	3 years
Number of shares of common stock that may be issued (in shares)	1,000,000
Stock Option Awards [Abstract]
Total unrecognized compensation costs	$ 8.9
Weighted average period for recognition of unrecognized compensation costs	1 year 9 months 18 days
Restricted Stock Awards
Restricted Stock Awards [Abstract]
Vested restricted stock withheld for tax withholding obligations (in shares)	35,514	30,712	31,688
Vested restricted stock withheld for tax withholding obligations, weighted average price (in dollars per share)	$ 63.83	$ 57.29	$ 50.65
Fair value, restricted stock	$ 8.9	$ 6.3	$ 6.4
Actual tax benefit realized	$ 3.3	$ 2.4	$ 2.4
Restricted Stock Awards \| Performance Vesting
Restricted Stock Awards [Abstract]
Vested (in shares)	78,825
Restricted Stock Awards \| Performance Vesting \| Executive Officers and Key Employees
Restricted Stock Awards [Abstract]
Granted, weighted average grant date fair value (in dollars per share)		$ 45.95	$ 36.69
Restricted Stock Awards \| Time Vesting
Restricted Stock Awards [Abstract]
Granted (in shares)	44,090
Granted, weighted average grant date fair value (in dollars per share)	$ 63.15
Vested (in shares)	58,200
Restricted Stock Awards \| Time Vesting \| Executive Officers and Key Employees
Restricted Stock Awards [Abstract]
Granted (in shares)	33,240
Granted, weighted average grant date fair value (in dollars per share)	$ 63.05	59.40	50.90
Restricted Stock Awards \| Time Vesting \| Non Employee Directors
Restricted Stock Awards [Abstract]
Granted (in shares)	10,850
Granted, weighted average grant date fair value (in dollars per share)	$ 63.45	$ 63.93	$ 54.66
Stock Option Awards
Stock Option Awards [Abstract]
Cash received from the exercise of stock options		$ 0.7	$ 1.5
Intrinsic value of exercised		$ 0.7	$ 0.9

STOCK-BASED COMPENSATION - Rest

STOCK-BASED COMPENSATION - Restricted Stock and Restricted Stock Unit Activity (Details) - Restricted Stock Awards	12 Months Ended
	Sep. 30, 2017$ / sharesshares
Performance Vesting
Shares/ Units
Nonvested at beginning of period (in shares) \| shares	510,583
Vested (in shares) \| shares	(78,825)
Forfeited (in shares) \| shares	(64,128)
Nonvested at end of period (in shares) \| shares	282,015
Weighted Average Grant Date Fair Value Per Share
Nonvested at beginning of period (in dollars per share) \| $ / shares	$ 40.37
Vested (in dollars per share) \| $ / shares	42.37
Forfeited (in dollars per share) \| $ / shares	33.03
Nonvested at end of period (in dollars per share) \| $ / shares	$ 56.32
Time Vesting
Shares/ Units
Nonvested at beginning of period (in shares) \| shares	132,779
Granted (in shares) \| shares	44,090
Vested (in shares) \| shares	(58,200)
Forfeited (in shares) \| shares	(7,729)
Nonvested at end of period (in shares) \| shares	110,940
Weighted Average Grant Date Fair Value Per Share
Nonvested at beginning of period (in dollars per share) \| $ / shares	$ 49.83
Granted (in dollars per share) \| $ / shares	63.15
Vested (in dollars per share) \| $ / shares	47.67
Forfeited (in dollars per share) \| $ / shares	55.58
Nonvested at end of period (in dollars per share) \| $ / shares	$ 55.85
Maximum \| Performance Vesting
Shares/ Units
Granted (in shares) \| shares	196,400
Nonvested at end of period (in shares) \| shares	564,030
Weighted Average Grant Date Fair Value Per Share
Granted (in dollars per share) \| $ / shares	$ 45.01
Nonvested at end of period (in dollars per share) \| $ / shares	$ 42.51

STOCK-BASED COMPENSATION - Fair

STOCK-BASED COMPENSATION - Fair Value Measurement Assumptions (Details)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	1.39%	1.14%	0.83%
Expected dividend yield of stock	0.00%	0.00%	0.00%
Expected volatility of stock	16.30%	15.00%	14.00%
Vesting period	2 years 9 months 18 days	2 years 9 months 18 days	2 years 9 months 18 days

STOCK-BASED COMPENSATION - Comp

STOCK-BASED COMPENSATION - Compensation Costs Recognized (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total compensation cost	$ 7.4	$ 6.7	$ 6.7
Compensation cost capitalized	(3.3)	(2.2)	(1.8)
Compensation cost recognized in net income	4.1	4.5	4.9
Income tax benefit recognized in net income	(1.5)	(1.7)	(1.9)
Compensation cost recognized in net income, net of income tax	$ 2.6	$ 2.8	$ 3

EARNINGS PER COMMON SHARE (Deta

EARNINGS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	Apr. 03, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Basic EPS:
Net income		$ (13.3)	$ 21.7	$ 108	$ 45.2	$ (14.2)	$ 10.7	$ 100.8	$ 46.9	$ 161.6	$ 144.2	$ 136.9
Less: Income allocated to participating securities										0.4	0.5	0.5
Net Income Available to Common Shareholders										$ 161.2	$ 143.7	$ 136.4
Weighted Average Shares Outstanding, Basic (in Shares)										46,900	44,100	43,200
Earnings Per Share of Common Stock (in dollars per share)		$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ (0.31)	$ 0.24	$ 2.32	$ 1.08	$ 3.44	$ 3.26	$ 3.16
Diluted EPS:
Net income		$ (13.3)	$ 21.7	$ 108	$ 45.2	$ (14.2)	$ 10.7	$ 100.8	$ 46.9	$ 161.6	$ 144.2	$ 136.9
Less: Income allocated to participating securities										0.4	0.5	0.5
Net Income Available to Common Shareholders										$ 161.2	$ 143.7	$ 136.4
Weighted Average Shares Outstanding, Basic (in Shares)										46,900	44,100	43,200
Dilutive Effect of Stock Options, Restricted Stock, and Restricted Stock Units (in shares)										100	200	100
Weighted Average Diluted Shares (in shares)										47,000	44,300	43,300
Earnings Per Share of Common Stock (in dollars per share)		$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ (0.31)	$ 0.24	$ 2.31	$ 1.08	$ 3.43	$ 3.24	$ 3.16
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares excluded from calculation of diluted EPS (in shares)	2,500									2,875
Restricted stock and stock units subject to performance and/or market conditions
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares excluded from calculation of diluted EPS (in shares)										500	300	300

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Details) $ / shares in Units, equity_unit in Thousands	Sep. 15, 2017USD ($)	Apr. 03, 2017$ / sharesshares	May 17, 2016USD ($)shares	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)shares	Sep. 30, 2015USD ($)	Dec. 31, 2014USD ($)equity_unit	May 30, 2017USD ($)	Nov. 11, 2016shares	Feb. 10, 2016USD ($)	Jun. 30, 2014$ / shares	Jun. 20, 2014shares
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Number of equity units issued (in shares) \| equity_unit							2,875
Stated value per Corporate Unit (in dollars per share) \| $ / shares											$ 50,000,000
Interest rate on Subordinated borrowing							2.00%
Issuance of stock (in shares)			2,185,000
SEC effective shelf registration Form S-3 sale and issuance authorization under the dividend reinvestment and stock purchase program (in shares)												250,000
SEC effective shelf registration Form S-3 remaining and available for issuance under the dividend reinvestment and stock purchase program (in shares)				244,130					239,945
Issuance of common stock \| $			$ 133,200,000	$ 145,500,000	$ 133,200,000
Preferred stock shares authorized (in shares)				5,000,000	5,000,000
Preferred stock shares issued (in shares)				0	0
Preferred stock shares outstanding (in shares)				0	0
Dividend payment restriction formula component - fixed amount \| $				$ 8,000,000
Retained earnings available to pay dividends in period \| $				$ 1,010,800,000	$ 916,800,000
Sale of Stock, Number of Shares Issued in Transaction		2,504,684
Sale of Stock, Price Per Share \| $ / shares		$ 57.3921
Share Purchase Obligation, Conversion to Common Stock, Rate Per Share		0.8712
Spire Missouri
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Preferred stock shares authorized (in shares)				1,480,000	1,480,000
Regulatory preferred stock and debt securities issuance, amount authorized \| $				$ 300,000,000				$ 300,000,000		$ 300,000,000
Proceeds from Issuance of Debt \| $	$ 170,000,000
Regulatory Preferred Stock and Debt Securities Issuance, Remaining Authorized Amount \| $				$ 130,000,000
Spire Missouri \| Affiliated Entity
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Issuance of stock (in shares)					0
Spire Alabama
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Issuance of common stock \| $						$ (27,000,000)
Preferred stock shares authorized (in shares)				120,000	120,000
Preferred stock shares issued (in shares)				0	0
Preferred stock shares outstanding (in shares)				0	0
Regulatory preferred stock and debt securities issuance, amount authorized \| $				$ 75,000,000
Junior Subordinated Debt
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Proceeds from convertible debt \| $							$ 143,800,000

STOCKHOLDERS' EQUITY - Stock Pu

STOCKHOLDERS' EQUITY - Stock Purchase Obligation (Details)	12 Months Ended
STOCKHOLDERS' EQUITY - Stock Purchase Obligation (Details)	Sep. 30, 2017shares / contract$ / shares	Jun. 30, 2014$ / shares
Stock Purchase Obligation [Line Items]
Stated value per Corporate Unit (in dollars per share)		$ 50,000,000
Equal to or greater than $57.8125
Stock Purchase Obligation [Line Items]
Market value per share of common stock (in dollars per share)	$ 57.8125
Number of shares to be purchased per purchase contract \| shares / contract	0.8649
Less than $57.8125, but greater than $46.25 \| Minimum
Stock Purchase Obligation [Line Items]
Market value per share of common stock (in dollars per share)	$ 46.25
Less than $57.8125, but greater than $46.25 \| Maximum
Stock Purchase Obligation [Line Items]
Market value per share of common stock (in dollars per share)	57.8125
Less than or equal to $46.25
Stock Purchase Obligation [Line Items]
Market value per share of common stock (in dollars per share)	$ 46.25
Number of shares to be purchased per purchase contract \| shares / contract	1.0811

STOCKHOLDERS' EQUITY - Schedule

STOCKHOLDERS' EQUITY - Schedule of Company's Equity Units (Details) equity_unit in Thousands	12 Months Ended
	Dec. 31, 2014equity_unit
Stockholders' Equity Note [Abstract]
Number of equity units issued (in shares)	2,875

STOCKHOLDERS' EQUITY - Schedu63

STOCKHOLDERS' EQUITY - Schedule of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	$ 1,768.2	$ 1,573.6	$ 1,508.4
Other comprehensive loss	7.4	(2.2)	(0.3)
BALANCE	1,991.3	1,768.2	1,573.6
Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	1,068.5	1,037.8	1,007.8
Other comprehensive loss	0.1	(0.1)	0.2
BALANCE	1,171	1,068.5	1,037.8
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(2.3)	(0.4)
Other comprehensive loss	7.2	(1.9)
BALANCE	4.9	(2.3)	(0.4)
Net Unrealized Gains (Losses) on Cash Flow Hedges \| Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	0.1	(0.2)
Other comprehensive loss	0	0.3
BALANCE	0.1	0.1	(0.2)
Defined Benefit Pension and Other Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(1.8)	(1.5)
Other comprehensive loss	0.3	(0.3)
BALANCE	(1.5)	(1.8)	(1.5)
Defined Benefit Pension and Other Postretirement Benefit Plans \| Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(1.8)	(1.5)
Other comprehensive loss	0.2	(0.3)
BALANCE	(1.6)	(1.8)	(1.5)
Net Unrealized Losses on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(0.1)	(0.1)
Other comprehensive loss	(0.1)	0
BALANCE	(0.2)	(0.1)	(0.1)
Net Unrealized Losses on Available for Sale Securities \| Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(0.1)	0
Other comprehensive loss	(0.1)	(0.1)
BALANCE	(0.2)	(0.1)	0
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(4.2)	(2)	(1.7)
Other comprehensive loss	7.4	(2.2)	(0.3)
BALANCE	3.2	(4.2)	(2)
AOCI \| Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(1.8)	(1.7)	(1.9)
Other comprehensive loss	0.1	(0.1)	0.2
BALANCE	$ (1.7)	$ (1.8)	$ (1.7)

LONG-TERM DEBT - Maturities of

LONG-TERM DEBT - Maturities of Long-term Debt (Details) $ in Millions	Sep. 30, 2017USD ($)
Maturities on long-term debt [Abstract]
2,018	$ 100
2,019	180
2,020	40
2,021	55
2,022	50
Spire Missouri
Maturities on long-term debt [Abstract]
2,018	100
2,019	50
2,020	0
2,021	0
2,022	0
Spire Alabama
Maturities on long-term debt [Abstract]
2,018	0
2,019	0
2,020	40
2,021	0
2,022	$ 50

LONG-TERM DEBT - Narrative (Det

LONG-TERM DEBT - Narrative (Details) $ / shares in Units, equity_unit in Thousands

Sep. 15, 2017USD ($)

Apr. 03, 2017USD ($)equity_unit$ / sharesshares

Feb. 22, 2017USD ($)

Jun. 11, 2014USD ($)$ / shares

Sep. 30, 2017USD ($)

Dec. 31, 2014USD ($)equity_unit

Sep. 30, 2014equity_unit

May 30, 2017USD ($)

Mar. 15, 2017USD ($)

Mar. 10, 2017USD ($)

Sep. 30, 2016

Feb. 10, 2016USD ($)

Jun. 30, 2014$ / shares

Debt Instrument [Line Items]

Long-term Debt, Gross

$ 2,112,000,000

Interest rate on Subordinated borrowing

2.00%

Number of equity units issued (in shares) | equity_unit

2,875

Stated value per Corporate Unit (in dollars per share) | $ / shares

$ 50,000,000

Percent of common stock equity

48.70%

46.10%

Percent of long-term debt

51.30%

53.90%

Sale of Stock, Number of Shares Issued in Transaction | shares

2,504,684

Sale of Stock, Price Per Share | $ / shares

$ 57.3921

Payment to Purchase Share, Price Per Share | $ / shares

$ 67.50

Share Purchase Obligation, Conversion to Common Stock, Rate Per Share

0.8712

Repayments of Short-term Debt

$ 142,000,000

Senior Notes

Debt Instrument [Line Items]

Long-term debt issued amount

$ 6,200,000

Proceeds from Issuance of Debt

150,000,000

Senior Notes | Senior Notes Due March 15, 2027

Debt Instrument [Line Items]

Long-term debt issued amount

$ 100,000,000

Stated interest rate on debt issued

3.93%

Senior Notes | Senior Notes Due in 2024

Debt Instrument [Line Items]

Long-term debt issued amount

$ 143,800,000

Stated interest rate on debt issued

3.543%

Senior Notes | One to six months prior to maturity | Subject to Callable at Par

Debt Instrument [Line Items]

Redemption period prior to maturity, minimum

1 month

Redemption period prior to maturity, maximum

6 months

Bonds | Bond Due September Fifteen Twenty Thirty Two [Member]

Debt Instrument [Line Items]

Long-term debt issued amount

$ 50,000,000

Stated interest rate on debt issued

3.68%

Bonds | Bond Due September Fifteen Twenty Forty Seven [Member]

Debt Instrument [Line Items]

Long-term debt issued amount

$ 70,000,000

Stated interest rate on debt issued

4.23%

Bonds | Bond Due September Fifteen Twenty Fifty Seven [Member]

Debt Instrument [Line Items]

Long-term debt issued amount

$ 50,000,000

Stated interest rate on debt issued

4.38%

Junior Subordinated Debt

Debt Instrument [Line Items]

Proceeds from convertible debt

$ 143,800,000

Notes Payable to Banks

Debt Instrument [Line Items]

Debt Instrument, Repurchase Amount

$ 250,000,000

Other subsidiaries

Debt Instrument [Line Items]

Long-term Debt, Gross

$ 67,000,000

Spire Missouri

Debt Instrument [Line Items]

Long-term Debt, Gross

980,000,000

Regulatory preferred stock and debt securities issuance, amount authorized

300,000,000

$ 300,000,000

Proceeds from Issuance of Debt

$ 170,000,000

Regulatory Preferred Stock and Debt Securities Issuance, Remaining Authorized Amount

130,000,000

Long-term debt

$ 975,000,000

Percent of common stock equity

54.60%

57.10%

Percent of long-term debt

45.40%

42.90%

Spire Missouri | No Call Options

Debt Instrument [Line Items]

Long-term Debt, Gross

$ 25,000,000

Long-term debt

25,000,000

Spire Missouri | Make Whole Call Options

Debt Instrument [Line Items]

Long-term Debt, Gross

1,037,000,000

Long-term debt

435,000,000

Spire Missouri | Subject to Callable Currently [Member]

Debt Instrument [Line Items]

Long-term Debt, Gross

5,000,000

Spire Missouri | Subject to Callable at Par

Debt Instrument [Line Items]

Long-term Debt, Gross

1,045,000,000

Long-term debt

$ 520,000,000

Spire Missouri | Three to six months prior to maturity | Subject to Callable at Par

Debt Instrument [Line Items]

Redemption period prior to maturity, minimum

3 months

Redemption period prior to maturity, maximum

6 months

Spire Alabama

Debt Instrument [Line Items]

Long-term Debt, Gross

$ 250,000,000

Regulatory preferred stock and debt securities issuance, amount authorized

75,000,000

Long-term debt

$ 250,000,000

Percent of common stock equity

77.80%

Percent of long-term debt

22.20%

Spire Alabama | Make Whole Call Options

Debt Instrument [Line Items]

Long-term debt

$ 250,000,000

Spire Alabama

Debt Instrument [Line Items]

Interest rate on Subordinated borrowing

2.00%

Number of equity units issued (in shares) | equity_unit

2,875

Stated value per Corporate Unit (in dollars per share) | $ / shares

$ 50

Spire Alabama | Junior Subordinated Debt

Debt Instrument [Line Items]

Proceeds from convertible debt

$ 143,800,000

NOTES PAYABLE AND CREDIT AGRE66

NOTES PAYABLE AND CREDIT AGREEMENTS - Narrative (Details)	12 Months Ended
NOTES PAYABLE AND CREDIT AGREEMENTS - Narrative (Details)	Sep. 30, 2017USD ($)	Sep. 30, 2016	Dec. 14, 2016bank
Line of Credit Facility [Line Items]
Long-term Line of Credit	$ 477,300,000
Speculative interest rate increase percent	1.00%
Decrease in cash flow with an impact of 100 basis point interest rate increase	$ 4,900,000
Spire Missouri
Line of Credit Facility [Line Items]
Long-term Line of Credit	203,000,000
Long-term debt	$ 975,000,000
Speculative interest rate increase percent	1.00%
Decrease in cash flow with an impact of 100 basis point interest rate increase	$ 2,800,000
Spire Alabama
Line of Credit Facility [Line Items]
Long-term Line of Credit	169,900,000
Long-term debt	$ 250,000,000
Speculative interest rate increase percent	1.00%
Decrease in cash flow with an impact of 100 basis point interest rate increase	$ 1,100,000
Spire Energy South Inc
Line of Credit Facility [Line Items]
Long-term Line of Credit	12,900,000
Spire STL Pipeline LLC
Line of Credit Facility [Line Items]
Long-term Line of Credit	26,600,000
Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	$ 975,000,000
Minimum required ratio of earnings before interest, taxes, depreciation, and amortization (EBITDA) times interest expense as required by the line of credit covenant	70.00%
Debt to total capitalization ratio	0.56
Line of Credit \| Spire Missouri
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	$ 475,000,000
Debt to total capitalization ratio	0.50
Line of Credit \| Spire Alabama
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	$ 200,000,000
Debt to total capitalization ratio	0.33
Line of Credit \| Liabilities \| Lender Concentration Risk
Line of Credit Facility [Line Items]
Line Of Credit Facility, Number Of Banks In Agreement \| bank			11
Percent of debt by a singe bank		12.30%
Subject to Callable at Par \| Spire Missouri
Line of Credit Facility [Line Items]
Long-term debt	$ 520,000,000
Spire \| Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	300,000,000
Other Affiliates
Line of Credit Facility [Line Items]
Long-term Line of Credit	27,600,000
Other subsidiaries
Line of Credit Facility [Line Items]
Long-term Line of Credit	$ 440,000,000

NOTES PAYABLE AND CREDIT AGRE67

NOTES PAYABLE AND CREDIT AGREEMENTS - Spire Short-term Borrowings (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2017	Sep. 30, 2016
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 485,800,000	$ 273,900,000
Weighted average interest rate		1.20%	0.90%
Minimum borrowing outstanding		$ 395,500,000	$ 73,100,000
Maximum borrowing outstanding		675,600,000	427,200,000
Short-term debt		$ 477,300,000	$ 398,700,000
Weighted average interest rate		1.50%	1.10%
Spire \| Line of Credit
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 369,000,000	$ 42,700,000
Weighted average interest rate		1.30%	1.60%
Minimum borrowing outstanding		$ 73,000,000	$ 0
Maximum borrowing outstanding		675,600,000	82,000,000
Short-term debt		$ 477,300,000	$ 73,000,000
Weighted average interest rate		1.50%	1.80%
Spire Missouri
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 284,000,000	$ 215,700,000
Weighted average interest rate		1.20%	0.70%
Minimum borrowing outstanding		$ 168,300,000	$ 127,800,000
Maximum borrowing outstanding		358,900,000	307,200,000
Short-term debt		$ 203,000,000	$ 243,700,000
Weighted average interest rate		1.50%	0.80%
Spire Missouri \| Commercial Paper
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 88,500,000	$ 201,000,000
Weighted average interest rate		0.90%	0.70%
Minimum borrowing outstanding		$ 0	$ 43,000,000
Maximum borrowing outstanding		329,700,000	307,200,000
Short-term debt		$ 0	$ 243,700,000
Weighted average interest rate		0.00%	0.80%
Spire Alabama
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 106,900,000	$ 42,600,000
Weighted average interest rate		1.50%	1.40%
Minimum borrowing outstanding		$ 74,000,000	$ 19,000,000
Maximum borrowing outstanding		171,000,000	82,000,000
Short-term debt		$ 169,900,000	$ 82,000,000
Weighted average interest rate		1.50%	1.50%
Spire Alabama \| Line of Credit
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 30,200,000	$ 28,300,000	$ 30,200,000
Weighted average interest rate	1.40%	1.60%	1.40%
Minimum borrowing outstanding		$ 0	$ 0
Maximum borrowing outstanding		102,500,000	82,000,000
Short-term debt		$ 0	$ 82,000,000
Weighted average interest rate		0.00%	1.50%

NOTES PAYABLE AND CREDIT AGRE68

NOTES PAYABLE AND CREDIT AGREEMENTS - Laclede Gas' Short-term Borrowings (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 485,800,000	$ 273,900,000
Weighted average interest rate	1.20%	0.90%
Minimum borrowing outstanding	$ 395,500,000	$ 73,100,000
Maximum borrowing outstanding	675,600,000	427,200,000
Short-term debt	$ 477,300,000	$ 398,700,000
Weighted average interest rate	1.50%	1.10%
Spire Missouri
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 284,000,000	$ 215,700,000
Weighted average interest rate	1.20%	0.70%
Minimum borrowing outstanding	$ 168,300,000	$ 127,800,000
Maximum borrowing outstanding	358,900,000	307,200,000
Short-term debt	$ 203,000,000	$ 243,700,000
Weighted average interest rate	1.50%	0.80%
Spire Missouri \| Commercial Paper
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 88,500,000	$ 201,000,000
Weighted average interest rate	0.90%	0.70%
Minimum borrowing outstanding	$ 0	$ 43,000,000
Maximum borrowing outstanding	329,700,000	307,200,000
Short-term debt	$ 0	$ 243,700,000
Weighted average interest rate	0.00%	0.80%
Spire Missouri \| Notes Payable to Related Party
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 195,500,000	$ 14,700,000
Weighted average interest rate	1.30%	0.80%
Minimum borrowing outstanding	$ 0	$ 0
Maximum borrowing outstanding	338,600,000	114,200,000
Short-term debt	$ 203,000,000	$ 0
Weighted average interest rate	1.50%	0.00%

NOTES PAYABLE AND CREDIT AGRE69

NOTES PAYABLE AND CREDIT AGREEMENTS - Alagasco's Short-term Borrowings (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2017	Sep. 30, 2016
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 485,800,000	$ 273,900,000
Weighted average interest rate		1.20%	0.90%
Minimum borrowing outstanding		$ 395,500,000	$ 73,100,000
Maximum borrowing outstanding		675,600,000	427,200,000
Short-term debt		$ 477,300,000	$ 398,700,000
Weighted average interest rate		1.50%	1.10%
Spire Alabama
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 106,900,000	$ 42,600,000
Weighted average interest rate		1.50%	1.40%
Minimum borrowing outstanding		$ 74,000,000	$ 19,000,000
Maximum borrowing outstanding		171,000,000	82,000,000
Short-term debt		$ 169,900,000	$ 82,000,000
Weighted average interest rate		1.50%	1.50%
Spire Alabama \| Line of Credit
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 30,200,000	$ 28,300,000	$ 30,200,000
Weighted average interest rate	1.40%	1.60%	1.40%
Minimum borrowing outstanding		$ 0	$ 0
Maximum borrowing outstanding		102,500,000	82,000,000
Short-term debt		$ 0	$ 82,000,000
Weighted average interest rate		0.00%	1.50%
Spire Alabama \| Notes Payable to Related Party
Short-term Debt [Line Items]
Weighted average borrowings outstanding		$ 78,600,000	$ 12,400,000
Weighted average interest rate		1.40%	1.40%
Minimum borrowing outstanding		$ 0	$ 0
Maximum borrowing outstanding		171,000,000	61,900,000
Short-term debt		$ 169,900,000	$ 0
Weighted average interest rate		1.50%	0.00%

FAIR VALUE OF FINANCIAL INSTR70

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 7.4	$ 5.2	$ 13.8	$ 16.1
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7.4	5.2
Short-term debt	477.3	398.7
Long-term debt, including current portion	2,095	2,070.7
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7.4	5.2
Short-term debt	477.3	398.7
Long-term debt, including current portion	2,210.3	2,257.1
Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2.5	2.1	1.7	3.7
Spire Missouri \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2.5	2.1
Short-term debt	203	243.7
Long-term debt, including current portion	973.9	804.1
Spire Missouri \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2.5	2.1
Short-term debt	203	243.7
Long-term debt, including current portion	1,056.9	900.4
Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0.1	0	$ 7.2	$ 5.6
Spire Alabama \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0.1
Short-term debt	169.9	82
Long-term debt, including current portion	247.8	247.6
Spire Alabama \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0.1
Short-term debt	169.9	82
Long-term debt, including current portion	269.4	275.5
Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7.4	5.2
Short-term debt	0	0
Long-term debt, including current portion	0	0
Quoted Prices in Active Markets (Level 1) \| Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2.5	2.1
Short-term debt	0	0
Long-term debt, including current portion	0	0
Quoted Prices in Active Markets (Level 1) \| Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0.1
Short-term debt	0	0
Long-term debt, including current portion	0	0
Significant Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Short-term debt	477.3	398.7
Long-term debt, including current portion	2,210.3	2,257.1
Significant Observable Inputs (Level 2) \| Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Short-term debt	203	243.7
Long-term debt, including current portion	1,056.9	900.4
Significant Observable Inputs (Level 2) \| Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0
Short-term debt	169.9	82
Long-term debt, including current portion	$ 269.4	$ 275.5

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
ASSETS
Derivative asset after the effects of netting	$ 6.2	$ 13.3
LIABILITIES
Derivative liability after the effects of netting	8	4.9
Spire Missouri
ASSETS
Derivative asset after the effects of netting	0.1	4.9
LIABILITIES
Derivative liability after the effects of netting	0	0.2
Fair Value, Measurements, Recurring
ASSETS
Effects of netting and cash margin receivables/payables	(6.7)	(5)
Derivative asset after the effects of netting	28.7	34.3
LIABILITIES
Effects of netting and cash margin receivables/payables	(5.2)
Derivative liability after the effects of netting	8.1
Fair Value, Measurements, Recurring \| Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	(3.4)	(0.7)
Derivative asset after the effects of netting	22.5	25.8
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.9)	(1.6)
Derivative liability after the effects of netting	0	0.2
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	23.1	22.9
LIABILITIES
Derivative liability before effects of netting	3.7
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	21.8	22.4
LIABILITIES
Derivative liability before effects of netting	1.9	1.6
Fair Value, Measurements, Recurring \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	12.2	16.2
LIABILITIES
Derivative liability before effects of netting	9.6
Fair Value, Measurements, Recurring \| Significant Observable Inputs (Level 2) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	4.1	4.1
LIABILITIES
Derivative liability before effects of netting	0	0.2
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0.1	0.2
LIABILITIES
Derivative liability before effects of netting	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting	0	0
Fair Value, Measurements, Recurring \| US stock/bond mutual funds \| Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	0	0
Derivative asset after the effects of netting	22.4	20.9
Fair Value, Measurements, Recurring \| US stock/bond mutual funds \| Quoted Prices in Active Markets (Level 1) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	18.3	16.8
Fair Value, Measurements, Recurring \| US stock/bond mutual funds \| Significant Observable Inputs (Level 2) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	4.1	4.1
Fair Value, Measurements, Recurring \| US stock/bond mutual funds \| Significant Unobservable Inputs (Level 3) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
Fair Value, Measurements, Recurring \| NYMEX/ICE natural gas contracts \| Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	(3.4)	(0.4)
Derivative asset after the effects of netting	0	4.9
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.9)	(1.6)
Derivative liability after the effects of netting	0	0
Fair Value, Measurements, Recurring \| NYMEX/ICE natural gas contracts \| Quoted Prices in Active Markets (Level 1) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	3.4	5.3
LIABILITIES
Derivative liability before effects of netting	1.9	1.6
Fair Value, Measurements, Recurring \| NYMEX/ICE natural gas contracts \| Significant Observable Inputs (Level 2) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting	0	0
Fair Value, Measurements, Recurring \| NYMEX/ICE natural gas contracts \| Significant Unobservable Inputs (Level 3) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting	0	0
Fair Value, Measurements, Recurring \| OTCBB natural gas contracts \| Spire Missouri
LIABILITIES
Effects of netting and cash margin receivables/payables		0
Derivative liability after the effects of netting		0.2
Fair Value, Measurements, Recurring \| OTCBB natural gas contracts \| Quoted Prices in Active Markets (Level 1) \| Spire Missouri
LIABILITIES
Derivative liability before effects of netting		0
Fair Value, Measurements, Recurring \| OTCBB natural gas contracts \| Significant Observable Inputs (Level 2) \| Spire Missouri
LIABILITIES
Derivative liability before effects of netting		0.2
Fair Value, Measurements, Recurring \| OTCBB natural gas contracts \| Significant Unobservable Inputs (Level 3) \| Spire Missouri
LIABILITIES
Derivative liability before effects of netting		0
Fair Value, Measurements, Recurring \| Gasoline and heating oil contracts \| Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	0	(0.3)
Derivative asset after the effects of netting	0.1	0
Fair Value, Measurements, Recurring \| Gasoline and heating oil contracts \| Quoted Prices in Active Markets (Level 1) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0.1	0.3
Fair Value, Measurements, Recurring \| Gasoline and heating oil contracts \| Significant Observable Inputs (Level 2) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
Fair Value, Measurements, Recurring \| Gasoline and heating oil contracts \| Significant Unobservable Inputs (Level 3) \| Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts
ASSETS
Effects of netting and cash margin receivables/payables		(0.3)
Derivative asset after the effects of netting		0.1
Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting		0.4
Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting		0
Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting		0
Fair Value, Measurements, Recurring \| Gas Marketing:
LIABILITIES
Effects of netting and cash margin receivables/payables		7.6
Derivative liability after the effects of netting		4.9
Fair Value, Measurements, Recurring \| Gas Marketing: \| Quoted Prices in Active Markets (Level 1)
LIABILITIES
Derivative liability before effects of netting		5.1
Fair Value, Measurements, Recurring \| Gas Marketing: \| Significant Observable Inputs (Level 2)
LIABILITIES
Derivative liability before effects of netting		7.4
Fair Value, Measurements, Recurring \| Gas Marketing: \| Significant Unobservable Inputs (Level 3)
LIABILITIES
Derivative liability before effects of netting		0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| US stock/bond mutual funds
ASSETS
Effects of netting and cash margin receivables/payables	0	0
Derivative asset after the effects of netting	22.4	20.9
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| US stock/bond mutual funds \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	18.3	16.8
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| US stock/bond mutual funds \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	4.1	4.1
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| US stock/bond mutual funds \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| NYMEX/ICE natural gas contracts
ASSETS
Effects of netting and cash margin receivables/payables	(3.4)	(0.4)
Derivative asset after the effects of netting	0	4.9
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.9)	(1.6)
Derivative liability after the effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| NYMEX/ICE natural gas contracts \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	3.4	5.3
LIABILITIES
Derivative liability before effects of netting	1.9	1.6
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| NYMEX/ICE natural gas contracts \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| NYMEX/ICE natural gas contracts \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| OTCBB natural gas contracts
LIABILITIES
Effects of netting and cash margin receivables/payables		0
Derivative liability after the effects of netting		0.2
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| OTCBB natural gas contracts \| Quoted Prices in Active Markets (Level 1)
LIABILITIES
Derivative liability before effects of netting		0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| OTCBB natural gas contracts \| Significant Observable Inputs (Level 2)
LIABILITIES
Derivative liability before effects of netting		0.2
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| OTCBB natural gas contracts \| Significant Unobservable Inputs (Level 3)
LIABILITIES
Derivative liability before effects of netting		0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts
ASSETS
Effects of netting and cash margin receivables/payables	0
Derivative asset after the effects of netting	0.1
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	0.1
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Utility: \| Gasoline and heating oil contracts \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts
ASSETS
Effects of netting and cash margin receivables/payables	(2.1)
Derivative asset after the effects of netting	0.5
LIABILITIES
Effects of netting and cash margin receivables/payables	(2.1)	(5.1)
Derivative liability after the effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	1.3
LIABILITIES
Derivative liability before effects of netting	1.8	3.5
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	1.3
LIABILITIES
Derivative liability before effects of netting	0.3	1.6
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0
LIABILITIES
Derivative liability before effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts
ASSETS
Effects of netting and cash margin receivables/payables		(3.4)
Derivative asset after the effects of netting		0.4
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting		0.4
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting		3.4
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| NYMEX/ICE natural gas contracts \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting		0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| Natural gas commodity contracts
ASSETS
Effects of netting and cash margin receivables/payables	(1.2)	(0.9)
Derivative asset after the effects of netting	5.7	8
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.2)	(0.9)
Derivative liability after the effects of netting	7.2	1.7
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| Natural gas commodity contracts \| Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting	0	0
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| Natural gas commodity contracts \| Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	6.8	8.7
LIABILITIES
Derivative liability before effects of netting	8.4	2.6
Operating Segments \| Fair Value, Measurements, Recurring \| Gas Marketing: \| Natural gas commodity contracts \| Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0.1	0.2
LIABILITIES
Derivative liability before effects of netting	0	0
Other \| Fair Value, Measurements, Recurring \| Interest rate swaps
LIABILITIES
Effects of netting and cash margin receivables/payables	0	0
Derivative liability after the effects of netting	0.9	3
Other \| Fair Value, Measurements, Recurring \| Interest rate swaps \| Quoted Prices in Active Markets (Level 1)
LIABILITIES
Derivative liability before effects of netting	0	0
Other \| Fair Value, Measurements, Recurring \| Interest rate swaps \| Significant Observable Inputs (Level 2)
LIABILITIES
Derivative liability before effects of netting	0.9	3
Other \| Fair Value, Measurements, Recurring \| Interest rate swaps \| Significant Unobservable Inputs (Level 3)
LIABILITIES
Derivative liability before effects of netting	$ 0	$ 0

DERIVATIVE INSTRUMENTS AND HE72

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES Narrative (Details) gal in Millions, MMBTU in Millions	May 21, 2015USD ($)	Sep. 30, 2017USD ($)MMBTU$ / galgal	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Dec. 01, 2015USD ($)	Sep. 15, 2015USD ($)	Apr. 30, 2015USD ($)	Mar. 31, 2015USD ($)
Derivative [Line Items]
Notional amount of non-exchange traded natural gas commodity contracts (in MMBtu) \| MMBTU		202.1
Notional amount of non-exchange traded natural gas commodity contracts to be settled during fiscal 2018 \| MMBTU		156.8
Notional amount of non-exchange traded natural gas commodity contracts to be settled during fiscal 2019 \| MMBTU		34.3
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2020 \| MMBTU		5.9
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2021 \| MMBTU		4.1
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2022 \| MMBTU		0.9
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2023 \| MMBTU		0.1
Unrealized gain on energy-related derivatives		$ (6,000,000)	$ 100,000	$ 2,800,000
Gain (loss) to be reclassified within twelve months		0
Cash margin receivables not offset with derivatives		$ 4,000,000	2,900,000
Spire Alabama
Derivative [Line Items]
Unsecured debt				115,000,000				$ 115,000,000
Gasoline futures contracts notional amount (in gallons) \| gal		0.1
Average price of future contracts (dollars per gallon) \| $ / gal		1.28
Spire Alabama \| 3.21% Notes, due September 15, 2025
Derivative [Line Items]
Unsecured debt						$ 35,000,000
Spire Alabama \| Notes 4.31%, Due December 1, 2045
Derivative [Line Items]
Unsecured debt					$ 80,000,000
Spire Missouri
Derivative [Line Items]
MMBtu (millions) \| MMBTU		33.9
Gain (loss) to be reclassified within twelve months		$ 0
Cash margin receivables not offset with derivatives		$ 4,000,000	500,000
Gasoline futures contracts notional amount (in gallons) \| gal		0.3
Average price of future contracts (dollars per gallon) \| $ / gal		1.27
Designated as Hedging Instrument \| Interest rate swaps \| Spire Alabama
Derivative [Line Items]
Loss on termination and settlement of interest rate swap		$ 900,000
Gain on settlement of derivative	$ 2,700,000	14,100,000		2,700,000
Designated as Hedging Instrument \| Interest rate swaps \| Spire Energy South Inc
Derivative [Line Items]
Loss on termination and settlement of interest rate swap			400,000
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps
Derivative [Line Items]
Notional amount							$ 24,000,000
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps \| Spire Alabama
Derivative [Line Items]
Notional amount		$ 60,000,000	225,000,000	$ 104,500,000				$ 80,500,000
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps \| Spire Alabama \| Minimum
Derivative [Line Items]
Derivative fixed interest rate		265.80%						2.18%
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps \| Spire Alabama \| Maximum
Derivative [Line Items]
Derivative fixed interest rate								2.85%
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps \| Spire Energy South Inc
Derivative [Line Items]
Notional amount			$ 85,000,000

DERIVATIVE INSTRUMENTS AND HE73

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Exchange-Traded/Cleared Derivatives (Details) MMBTU in Thousands	12 Months Ended
	Sep. 30, 2017MMBTU$ / MMBTU$ / gal
Spire Missouri
Derivative [Line Items]
MMBtu (millions)	33,900
Avg. Price Per MMBtu \| $ / gal	1.27
Natural gas contracts \| Fiscal 2021 \| Spire Missouri
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Natural gas contracts \| Fiscal 2021 \| Spire marketing
Derivative [Line Items]
MMBtu (millions)	280
Avg. Price Per MMBtu \| $ / MMBTU	2.90
Natural gas contracts \| Fiscal 2022 \| Spire Missouri
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Natural gas contracts \| Fiscal 2022 \| Spire marketing
Derivative [Line Items]
MMBtu (millions)	220
Avg. Price Per MMBtu \| $ / MMBTU	3
Short \| Gas Utility: \| Natural gas contracts \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Short \| Gas Utility: \| Natural gas contracts \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Short \| Gas Utility: \| ICE open daily swap positions [Member] \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Short \| Gas Utility: \| ICE Open basis swap positions \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Short \| Gas Utility: \| ICE Open basis swap positions \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Short \| Gas Utility: \| ICE Open basis swap positions \| Fiscal 2020
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Short \| Gas Marketing: \| Natural gas contracts \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	8,660
Avg. Price Per MMBtu \| $ / MMBTU	3.34
Short \| Gas Marketing: \| Natural gas contracts \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	2,070
Avg. Price Per MMBtu \| $ / MMBTU	3.13
Short \| Gas Marketing: \| ICE open daily swap positions [Member] \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	1,320
Avg. Price Per MMBtu \| $ / MMBTU	2.87
Short \| Gas Marketing: \| ICE Open basis swap positions \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	14,040
Avg. Price Per MMBtu \| $ / MMBTU	0.10
Short \| Gas Marketing: \| ICE Open basis swap positions \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	3,350
Avg. Price Per MMBtu \| $ / MMBTU	0.27
Short \| Gas Marketing: \| ICE Open basis swap positions \| Fiscal 2020
Derivative [Line Items]
MMBtu (millions)	310
Avg. Price Per MMBtu \| $ / MMBTU	0.36
Long \| Gas Utility: \| Natural gas contracts \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	14,180
Avg. Price Per MMBtu \| $ / MMBTU	2.98
Long \| Gas Utility: \| Natural gas contracts \| Fiscal 2018 \| Spire Missouri
Derivative [Line Items]
MMBtu (millions)	14,180
Avg. Price Per MMBtu \| $ / MMBTU	2.98
Long \| Gas Utility: \| Natural gas contracts \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	1,680
Avg. Price Per MMBtu \| $ / MMBTU	2.89
Long \| Gas Utility: \| Natural gas contracts \| Fiscal 2019 \| Spire Missouri
Derivative [Line Items]
MMBtu (millions)	1,680
Avg. Price Per MMBtu \| $ / MMBTU	2.89
Long \| Gas Utility: \| Natural gas contracts \| Fiscal 2020
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Long \| Gas Utility: \| ICE open daily swap positions [Member] \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Long \| Gas Utility: \| ICE Open basis swap positions \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Long \| Gas Utility: \| ICE Open basis swap positions \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Long \| Gas Utility: \| ICE Open basis swap positions \| Fiscal 2020
Derivative [Line Items]
MMBtu (millions)	0
Avg. Price Per MMBtu \| $ / MMBTU	0
Long \| Gas Marketing: \| Natural gas contracts \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	3,780
Avg. Price Per MMBtu \| $ / MMBTU	3.16
Long \| Gas Marketing: \| Natural gas contracts \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	1,840
Avg. Price Per MMBtu \| $ / MMBTU	3.02
Long \| Gas Marketing: \| Natural gas contracts \| Fiscal 2020
Derivative [Line Items]
MMBtu (millions)	660
Avg. Price Per MMBtu \| $ / MMBTU	2.91
Long \| Gas Marketing: \| ICE open daily swap positions [Member] \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	780
Avg. Price Per MMBtu \| $ / MMBTU	2.79
Long \| Gas Marketing: \| ICE Open basis swap positions \| Fiscal 2018
Derivative [Line Items]
MMBtu (millions)	11,120
Avg. Price Per MMBtu \| $ / MMBTU	0.38
Long \| Gas Marketing: \| ICE Open basis swap positions \| Fiscal 2019
Derivative [Line Items]
MMBtu (millions)	4,510
Avg. Price Per MMBtu \| $ / MMBTU	0.45
Long \| Gas Marketing: \| ICE Open basis swap positions \| Fiscal 2020
Derivative [Line Items]
MMBtu (millions)	620
Avg. Price Per MMBtu \| $ / MMBTU	0.45

DERIVATIVE INSTRUMENTS AND HE74

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Gains (Losses) on Derivative Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Designated as Hedging Instrument \| Cash Flow Hedging
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	$ 0	$ (1.1)	$ (4.4)
Ineffective portion of gain (loss) on derivatives recognized in income	0.5	0.3	(0.4)
Designated as Hedging Instrument \| Cash Flow Hedging \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives	11.5	(4)	(5.5)
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	(0.3)	(0.6)	(3.5)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.2	(0.5)
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives	0	(0.6)	(4.3)
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts \| Gas Marketing Operating Revenues
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	(0.4)	4.3	1.7
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.1	0
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts \| Gas Marketing Operating Expenses
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	0.1	(4.9)	(5.2)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.1	(0.5)
Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives	0.1	0	(1.2)
Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Gas Utility Other Operating Expenses
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	0.2	(0.5)	(0.9)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.1	0.1
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest rate swaps \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives	11.4	(3.4)	0
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest rate swaps \| Interest Expense
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	0.1	0	0
Ineffective portion of gain (loss) on derivatives recognized in income	0.5	0	0
Not Designated as Hedging Instrument
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	(3.7)	10.6	(11.1)
Not Designated as Hedging Instrument \| Gasoline and heating oil contracts \| Other Income and (Income Deductions) - Net
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	0	0	(0.2)
Not Designated as Hedging Instrument \| Natural gas commodity contracts \| Gas Marketing Operating Revenues
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	0.7	12.3	(1.3)
Not Designated as Hedging Instrument \| NYMEX / ICE natural gas contracts \| Gas Marketing Operating Revenues
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	(4.4)	(1.7)	(9.6)
Spire Missouri \| Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives	0.1	0	(1.2)
Spire Missouri \| Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Gas Utility Other Operating Expenses
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	0.2	(0.5)	(0.9)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.1	0.1
Spire Missouri \| Not Designated as Hedging Instrument \| Gasoline and heating oil contracts \| Other Income and (Income Deductions) - Net
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	$ 0	$ 0	$ (0.2)

DERIVATIVE INSTRUMENTS AND HE75

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	$ 13	$ 18.4
Fair value of liability derivatives presented above	13.3	12.5
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.7
Fair value of liability derivatives presented above	1.1
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	12.3	15.2
Fair value of liability derivatives presented above	12.2	8.6
Gas Utility: \| Operating Segments \| Gasoline and heating oil contracts \| Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.1	0.3
Fair value of liability derivatives presented above	0	0
Gas Utility: \| Operating Segments \| Natural gas contracts \| Not Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0
Fair value of liability derivatives presented above		0.2
Gas Utility: \| Operating Segments \| Natural gas contracts \| Not Designated as Hedging Instrument \| Accounts Receivable – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	3.4	5.4
Fair value of liability derivatives presented above	1.9	1.6
Gas Marketing: \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		3.2
Fair value of liability derivatives presented above		3.9
Gas Marketing: \| Natural gas contracts \| Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		2.5
Fair value of liability derivatives presented above		0.8
Gas Marketing: \| Interest rate swaps \| Designated as Hedging Instrument \| Current Liabilities – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0
Fair value of liability derivatives presented above	0.9
Gas Marketing: \| Operating Segments \| Natural gas contracts \| Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.3
Fair value of liability derivatives presented above	0.2
Gas Marketing: \| Operating Segments \| Natural gas contracts \| Designated as Hedging Instrument \| Deferred Charges – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.3	0.4
Fair value of liability derivatives presented above	0	0.1
Gas Marketing: \| Operating Segments \| Interest rate swaps \| Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0
Fair value of liability derivatives presented above		3
Gas Marketing: \| Operating Segments \| NYMEX / ICE natural gas contracts \| Not Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	1.7	0.8
Fair value of liability derivatives presented above	1.4	4.1
Gas Marketing: \| Operating Segments \| NYMEX / ICE natural gas contracts \| Not Designated as Hedging Instrument \| Deferred Charges – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.3	0
Fair value of liability derivatives presented above	0.5	0.1
Gas Marketing: \| Operating Segments \| Natural gas commodity contracts \| Not Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	5.3	6.5
Fair value of liability derivatives presented above	0.1	0.2
Gas Marketing: \| Operating Segments \| Natural gas commodity contracts \| Not Designated as Hedging Instrument \| Deferred Charges – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.4	2.1
Fair value of liability derivatives presented above	0	0.3
Gas Marketing: \| Operating Segments \| Natural gas commodity contracts \| Not Designated as Hedging Instrument \| Current Liabilities – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.8	0.2
Fair value of liability derivatives presented above	5	2
Gas Marketing: \| Operating Segments \| Natural gas commodity contracts \| Not Designated as Hedging Instrument \| Deferred Credits – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.4	0.2
Fair value of liability derivatives presented above	3.3	0.1
Spire Missouri
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	3.5	5.7
Fair value of liability derivatives presented above	1.9	1.8
Spire Missouri \| Gas Utility:
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	3.5	5.7
Fair value of liability derivatives presented above	1.9	1.8
Spire Missouri \| Gas Utility: \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0.3
Fair value of liability derivatives presented above		0
Spire Missouri \| Gas Utility: \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		5.4
Fair value of liability derivatives presented above		1.8
Spire Missouri \| Gas Utility: \| Gasoline and heating oil contracts \| Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	0.1
Fair value of liability derivatives presented above	0
Spire Missouri \| Gas Utility: \| Gasoline and heating oil contracts \| Designated as Hedging Instrument \| Accounts Receivable – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0.3
Fair value of liability derivatives presented above		0
Spire Missouri \| Gas Utility: \| Natural gas contracts \| Not Designated as Hedging Instrument \| Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0
Fair value of liability derivatives presented above		0.2
Spire Missouri \| Gas Utility: \| Natural gas contracts \| Not Designated as Hedging Instrument \| Accounts Receivable – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	3.4	5.4
Fair value of liability derivatives presented above	$ 1.9	$ 1.6

DERIVATIVE INSTRUMENTS AND HE76

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Instruments Reconciliation (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Offsetting Derivative Assets [Abstract]
Fair value of asset derivatives presented above	$ 13	$ 18.4
Fair value of cash margin receivables offset with derivatives	(1.5)	2.5
Netting of assets and liabilities with the same counterparty	(5.3)	(7.6)
Derivative asset after the effects of netting	6.2	13.3
Derivative instrument assets	5.9	11.4
Deferred Charges – Other	0.3	1.9
Offsetting Derivative Liabilities [Abstract]
Fair value of liability derivatives presented above	13.3	12.5
Netting of assets and liabilities with the same counterparty	(5.3)	(7.6)
Derivative liability after the effects of netting	8	4.9
Current Liabilities – Other	4.9	4.8
Deferred Credits – Other	3.1	0.1
Spire Missouri
Offsetting Derivative Assets [Abstract]
Fair value of asset derivatives presented above	3.5	5.7
Fair value of cash margin receivables offset with derivatives	(1.5)	0.8
Netting of assets and liabilities with the same counterparty	(1.9)	(1.6)
Derivative asset after the effects of netting	0.1	4.9
Derivative instrument assets	0.1	4.9
Offsetting Derivative Liabilities [Abstract]
Fair value of liability derivatives presented above	1.9	1.8
Netting of assets and liabilities with the same counterparty	(1.9)	(1.6)
Derivative liability after the effects of netting	0	0.2
Current Liabilities – Other	$ 0	$ 0.2

CONCENTRATIONS OF CREDIT RISK (

CONCENTRATIONS OF CREDIT RISK (Details) $ in Millions	Sep. 30, 2017USD ($)counterparty
Concentration Risk [Line Items]
Number of large counterparties for which credit risk is disclosed \| counterparty	5
Energy Producers And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	$ 17.9
Net receivable amount	8.9
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	58.2
Net receivable amount	55.8
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	23.8
Net receivable amount	$ 23.1

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($)	Sep. 30, 2017	Sep. 30, 2016
Tax Credit Carryforward [Line Items]
Federal and state loss carryforwards	$ 478,600,000
Contribution carryforwards	12,100,000
Valuation allowance	500,000	$ 900,000
Tax credit carryforwards	2,500,000
Unrecognized tax benefits affect on the Company's effective tax rate	5,100,000	3,300,000
Income taxes accrued	0	0
income tax penalties accrued	0
Spire Missouri
Tax Credit Carryforward [Line Items]
Federal and state loss carryforwards	166,000,000
Contribution carryforwards	11,200,000
Valuation allowance	500,000	900,000
Tax credit carryforwards	2,000,000
Unrecognized tax benefits affect on the Company's effective tax rate	4,800,000	3,100,000
Income taxes accrued	0	0
income tax penalties accrued	0	$ 0
Spire Alabama
Tax Credit Carryforward [Line Items]
Federal and state loss carryforwards	$ 233,500,000

INCOME TAXES - Net Provisions f

INCOME TAXES - Net Provisions for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Federal
Current	$ 0.1	$ 0.1	$ (3.3)
Deferred	67.7	62	58.8
Investment tax credits	(0.2)	(0.2)	(0.2)
State and local
Current	0.5	0.6	0
Deferred	9.5	7	6.9
Total income tax expense	77.6	69.5	62.2
Spire Missouri
Federal
Current	0	0	(2.1)
Deferred	42	37.5	40.9
Investment tax credits	(0.2)	(0.2)	(0.2)
State and local
Current	0	0.1	(0.1)
Deferred	5.7	8	4.7
Total income tax expense	47.5	45.4	43.2
Spire Alabama
Federal
Current	0	(0.8)	0
Deferred	31.6	29.4	25.9
State and local
Current	0	0	0.1
Deferred	4.2	3.8	3.3
Total income tax expense	$ 35.8	$ 32.4	$ 29.3

INCOME TAXES - Effective Income

INCOME TAXES - Effective Income Tax Rate Variation from Stated Tax Rate (Details)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Contingency [Line Items]
Federal income tax statutory rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefits	2.80%	2.80%	3.00%
Certain expenses capitalized on books and deducted on tax return	(2.30%)	(3.40%)	(3.70%)
Taxes related to prior years	(0.90%)	(0.20%)	(0.60%)
Other items – net	(2.20%)	(1.70%)	(2.50%)
Effective income tax rate	32.40%	32.50%	31.20%
Spire Missouri
Income Tax Contingency [Line Items]
Federal income tax statutory rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefits	2.80%	2.80%	2.80%
Certain expenses capitalized on books and deducted on tax return	(3.50%)	(4.80%)	(4.90%)
Taxes related to prior years	(1.40%)	(0.20%)	(0.80%)
Other items – net	(3.30%)	(2.80%)	(3.00%)
Effective income tax rate	29.60%	30.00%	29.10%
Spire Alabama
Income Tax Contingency [Line Items]
Federal income tax statutory rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefits	2.80%	2.80%	2.80%
Other items – net	0.30%	0.10%	0.10%
Effective income tax rate	38.10%	37.90%	37.90%

INCOME TAXES - Significant Item

INCOME TAXES - Significant Items in Net Deferred Tax Liability (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Deferred tax assets:
Reserves not currently deductible	$ 31.5	$ 21.3
Pension and other postretirement benefits	58.6	68.3
Operating losses	169.6	102.3
Other	26	0
Deferred tax assets	285.7	191.9
Less: valuation allowance	0.5	0.9
Total deferred tax assets	285.2	191
Deferred tax liabilities:
Relating to property	728.3	623.1
Regulatory pension and other postretirement benefits	108	106.8
Deferred gas costs	30.6	20
Other	125.8	48.4
Total deferred tax liabilities	992.7	798.3
Net deferred tax liability	707.5	607.3
Spire Missouri
Deferred tax assets:
Reserves not currently deductible		14.9
Pension and other postretirement benefits		56.9
Operating losses		29.9
Deferred tax assets	130	101.7
Less: valuation allowance	0.5	0.9
Total deferred tax assets	129.5	100.8
Deferred tax liabilities:
Relating to property		497
Regulatory pension and other postretirement benefits		106.8
Deferred gas costs		20
Other		33.9
Total deferred tax liabilities	753.3	657.7
Net deferred tax liability	623.8	556.9
Spire Alabama
Deferred tax assets:
Reserves not currently deductible	6	6.3
Pension and other postretirement benefits	4.4	11.4
Goodwill	214.4	233.4
Operating losses	88.3	60.2
Deferred tax assets	313.1	311.3
Deferred tax liabilities:
Relating to property	119.3	87.6
Other	8.2	2.3
Total deferred tax liabilities	127.5	89.9
Net deferred tax asset	$ 185.6	$ 221.4

INCOME TAXES - Unrecognized Tax

INCOME TAXES - Unrecognized Tax Benefit Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, beginning of year	$ 10	$ 7.1	$ 4.6
Increases related to tax positions taken in current year	2.4	3.4	2.9
Reductions due to lapse of applicable statute of limitations	(1.4)	(0.5)	(0.4)
Unrecognized tax benefits, end of year	11	10	7.1
Spire Missouri
Unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, beginning of year	9.7	6.9	4.2
Increases related to tax positions taken in current year	2.4	3.3	2.9
Reductions due to lapse of applicable statute of limitations	(1.4)	(0.5)	(0.2)
Unrecognized tax benefits, end of year	$ 10.7	$ 9.7	$ 6.9

PENSION PLANS AND OTHER POSTR83

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Jan. 01, 2011	Feb. 20, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Extent of Lump-sum payments recognized, percentage	100.00%
Implementation period used to calculate return on plan assets	4 years
Gains or losses includible in cost amortized to extent exceeds benefit obligations or market-related value of plan assets, percentage	10.00%
Anticipated Contributions to pension plans for qualified trust	$ 35.5
Anticipated contributions to pension plans for non-qualified plans	$ 0.5
Medical insurance available until age is reached after early retirement	65 years
Recovery in rates for postretirement benefit				$ 9.5
Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Recovery in rates for the qualified pension plans base allowance				$ 15.5
Other Plans [Abstract]
401(K) plans, cost of defined contributions	$ 8.4	$ 8.2	$ 8
Spire Alabama
Other Plans [Abstract]
401(K) plans, cost of defined contributions	2.7	2.3	3
Spire Missouri West
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Recovery in rates for the qualified pension plans base allowance					$ 10
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement benefits paid	$ 62.2	$ 16.6	71.1
Pension Plans \| Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	100.00%	100.00%
Settlement benefits paid	$ 43.5	$ 0	58.2
Pension Plans \| Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	100.00%	100.00%
Settlement benefits paid	$ 18.7	$ 16.6	$ 12.9
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Anticipated contributions to the postretirement plans for qualified trusts	7.2
Anticipated payment directly to participants in postretirement plan	$ 0.2
Postretirement Plans \| Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	100.00%
Postretirement Plans \| Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	100.00%
Equity markets \| Pension Plans \| Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	56.40%	56.20%
Equity markets \| Pension Plans \| Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	60.00%	60.00%
Equity markets \| Postretirement Plans \| Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	60.00%
Equity markets \| Postretirement Plans \| Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	60.00%
Debt securities \| Pension Plans \| Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	43.60%	43.80%
Debt securities \| Postretirement Plans \| Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	40.00%
Debt securities \| Postretirement Plans \| Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets	40.00%

PENSION PLANS AND OTHER POSTR84

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Net Periodic Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	$ 20.5	$ 15.3	$ 17.3
Interest cost on projected benefit obligation	27.9	28	29.5
Expected return on plan assets	(38.5)	(34.9)	(37.4)
Amortization of prior service cost	1	0.4	0.5
Amortization of actuarial loss	12.5	8	7.5
Loss on lump-sum settlements and curtailments	17.9	3.3	19.6
Special termination benefits	0.9	1.6	0
Subtotal	42.2	21.7	37
Regulatory adjustment	(2.4)	17.8	(2.1)
Net benefit cost	39.8	39.5	34.9
Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	11	10.9	12.8
Interest cost on projected benefit obligation	8.6	10.2	11.2
Expected return on plan assets	(13.6)	(13.5)	(13.2)
Amortization of prior service cost	0	0.3	0.8
Amortization of actuarial loss	2.5	3.6	5.1
Special termination benefits	0	2.6	0
Subtotal	8.5	14.1	16.7
Regulatory adjustment	(3.2)	(6.6)	(11)
Net benefit cost	5.3	7.5	5.7
Spire Missouri \| Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	12.7	10	11.5
Interest cost on projected benefit obligation	19.5	21.7	23.3
Expected return on plan assets	(28.1)	(26.7)	(29.2)
Amortization of prior service cost	1	0.4	0.5
Amortization of actuarial loss	10.7	7.9	7.5
Loss on lump-sum settlements and curtailments	13.5	0	18
Special termination benefits	0	1.6	0
Subtotal	29.3	14.9	31.6
Regulatory adjustment	(4.1)	11.7	(5.2)
Net benefit cost	25.2	26.6	26.4
Spire Missouri \| Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	10.4	10.6	12.3
Interest cost on projected benefit obligation	6.8	8.1	8.6
Expected return on plan assets	(9)	(8.5)	(8.1)
Amortization of prior service cost	0.2	0.3	0.8
Amortization of actuarial loss	2.6	3.8	5.1
Special termination benefits	0	2.6	0
Subtotal	11	16.9	18.7
Regulatory adjustment	(1.5)	(4.8)	(9.2)
Net benefit cost	9.5	12.1	9.5
Spire Alabama \| Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	6.2	5.3	5.8
Interest cost on projected benefit obligation	6.1	6.3	6.2
Expected return on plan assets	(7.2)	(8.2)	(8.2)
Amortization of prior service cost	0	0	0
Amortization of actuarial loss	1.8	0.1	0
Loss on lump-sum settlements and curtailments	4.6	3.3	1.6
Special termination benefits	0	0	0
Subtotal	11.5	6.8	5.4
Regulatory adjustment	1.8	6.1	3.1
Net benefit cost	13.3	12.9	8.5
Spire Alabama \| Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	0.3	0.3	0.5
Interest cost on projected benefit obligation	1.6	2.1	2.6
Expected return on plan assets	(4.4)	(5)	(5.1)
Amortization of prior service cost	(0.2)	0	0
Amortization of actuarial loss	(0.1)	(0.2)	0
Special termination benefits	0	0	0
Subtotal	(2.8)	(2.8)	(2)
Regulatory adjustment	(1.8)	(1.8)	(1.8)
Net benefit cost	$ (4.6)	$ (4.6)	$ (3.8)

PENSION PLANS AND OTHER POSTR85

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Changes in Plan Assets and Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of actuarial loss	$ (0.4)	$ 0.3	$ (0.4)
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	14.1	46.8	48.3
Amortization of actuarial loss	(12.5)	(8)	(7.5)
Acceleration of loss recognized due to settlement	(18.2)	(3.3)	(19.6)
Current year service cost	0	5	0
Current year prior year service cost	(20.7)	0	0
Amortization of prior service cost	(1)	(0.4)	(0.5)
Subtotal	(38.3)	40.1	20.7
Regulatory adjustment	38	(39.8)	(21.2)
Total recognized in OCI	(0.3)	0.3	(0.5)
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	(34.1)	0.8	(8.5)
Amortization of actuarial loss	(2.5)	(3.6)	(5.1)
Current year prior year service cost	(1.4)	(1.8)	(4.9)
Amortization of prior service cost	0	(0.3)	(0.8)
Subtotal	(38)	(4.9)	(19.3)
Regulatory adjustment	38	4.9	19.3
Total recognized in OCI	0	0	0
Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of actuarial loss	(0.3)	0.3	(0.4)
Spire Missouri \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	14.8	21.6	26
Amortization of actuarial loss	(10.7)	(7.9)	(7.5)
Acceleration of loss recognized due to settlement	(13.5)	0	(18)
Current year service cost	0	5	0
Current year prior year service cost	0	0	0
Amortization of prior service cost	(1)	(0.4)	(0.5)
Subtotal	(10.4)	18.3	0
Regulatory adjustment	10.1	(18)	(0.5)
Total recognized in OCI	(0.3)	0.3	(0.5)
Spire Missouri \| Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	(28.5)	1.4	(2.4)
Amortization of actuarial loss	(2.6)	(3.8)	(5.1)
Current year prior year service cost	0	0	(4.9)
Amortization of prior service cost	(0.2)	(0.3)	(0.8)
Subtotal	(31.3)	(2.7)	(13.2)
Regulatory adjustment	31.3	2.7	13.2
Total recognized in OCI	0	0	0
Spire Alabama \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	3.3	25.2	22.3
Amortization of actuarial loss	(1.8)	(0.1)	0
Acceleration of loss recognized due to settlement	(4.5)	(3.3)	(1.6)
Current year service cost	0	0	0
Current year prior year service cost	(20.7)	0	0
Amortization of prior service cost	0	0	0
Subtotal	(23.7)	21.8	20.7
Regulatory adjustment	23.7	(21.8)	(20.7)
Total recognized in OCI	0	0	0
Spire Alabama \| Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	(4.5)	(0.6)	(6.1)
Amortization of actuarial loss	0.1	0.2	0
Current year prior year service cost	(1.4)	(1.8)	0
Amortization of prior service cost	0.2	0	0
Subtotal	(5.6)	(2.2)	(6.1)
Regulatory adjustment	5.6	2.2	6.1
Total recognized in OCI	$ 0	$ 0	$ 0

PENSION PLANS AND OTHER POSTR86

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Benefit Obligation Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	$ 794.7	$ 652.3
Service cost	20.5	15.3	$ 17.3
Interest cost	27.9	28	29.5
Actuarial (gain) loss	(0.9)	85.8
Plan amendments	(20.7)	5.1
Spire EnergySouth acquisition	0	60.4
Settlement loss	14.6	1.1
Special termination benefits	0.9	1.6
Settlement benefits paid	(62.2)	(16.6)	(71.1)
Regular benefits paid	(26)	(38.3)
Benefit obligation, end of year	748.8	794.7	652.3
Accumulated benefit obligation, end of year	701.4	724.5
Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	259.2	239.2
Service cost	11	10.9	12.8
Interest cost	8.6	10.2	11.2
Actuarial (gain) loss	(22.1)	7.1
Plan amendments	(1.4)	(1.8)
Spire EnergySouth acquisition	0	5.9
Special termination benefits	0	2.6
Curtailments	0.4	0
Retiree drug subsidy program	0.3	0.2
Regular benefits paid	(17.5)	(15.1)
Benefit obligation, end of year	238.5	259.2	239.2
Spire Missouri \| Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	560	497.6
Service cost	12.7	10	11.5
Interest cost	19.5	21.7	23.3
Actuarial (gain) loss	(0.5)	59.2
Plan amendments	0	5.1
Spire EnergySouth acquisition	0	0
Settlement loss	12.2	0
Special termination benefits	0	1.6
Settlement benefits paid	(43.5)	0	(58.2)
Regular benefits paid	(20.8)	(35.2)
Benefit obligation, end of year	539.6	560	497.6
Accumulated benefit obligation, end of year	500.4	517.7
Spire Missouri \| Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	207.9	191.9
Service cost	10.4	10.6	12.3
Interest cost	6.8	8.1	8.6
Actuarial (gain) loss	(20.9)	6.7
Plan amendments	0	0
Spire EnergySouth acquisition	0	0
Special termination benefits	0	2.6
Curtailments	0	0
Retiree drug subsidy program	0.3	0
Regular benefits paid	(12)	(12)
Benefit obligation, end of year	192.5	207.9	191.9
Spire Alabama \| Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	174.3	154.7
Service cost	6.2	5.3	5.8
Interest cost	6.1	6.3	6.2
Actuarial (gain) loss	1.6	26.6
Plan amendments	(20.7)	0
Spire EnergySouth acquisition	0	0
Settlement loss	2.4	1.1
Special termination benefits	0	0
Settlement benefits paid	(18.7)	(16.6)	(12.9)
Regular benefits paid	(3)	(3.1)
Benefit obligation, end of year	148.2	174.3	154.7
Accumulated benefit obligation, end of year	142.8	149.8
Spire Alabama \| Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	45.4	47.3
Service cost	0.3	0.3	0.5
Interest cost	1.6	2.1	2.6
Actuarial (gain) loss	0	0.4
Plan amendments	(1.4)	(1.8)
Spire EnergySouth acquisition	0	0
Special termination benefits	0	0
Curtailments	0	0
Retiree drug subsidy program	0	0.2
Regular benefits paid	(5.3)	(3.1)
Benefit obligation, end of year	$ 40.6	$ 45.4	$ 47.3

PENSION PLANS AND OTHER POSTR87

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Pension Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	$ 540.5	$ 448.9
Actual return on plan assets	38	75.1
Employer contributions	41.3	26.6
Spire EnergySouth acquisition	0	44.8
Settlement benefits paid	(62.2)	(16.6)	$ (71.1)
Regular benefits paid	(26)	(38.3)
Fair value of plan assets, end of year	531.6	540.5	448.9
Funded status of plans, end of year	(217.2)	(254.2)
Postretirement Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	246.4	223.3
Actual return on plan assets	26.2	19.9
Employer contributions	10.4	14.3
Spire EnergySouth acquisition	0	4
Regular benefits paid	(17.5)	(15.1)
Fair value of plan assets, end of year	265.5	246.4	223.3
Funded status of plans, end of year	27	(12.8)
Spire Missouri \| Pension Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	395.7	339.9
Actual return on plan assets	25.1	64.4
Employer contributions	29.4	26.6
Spire EnergySouth acquisition	0	0
Settlement benefits paid	(43.5)	0	(58.2)
Regular benefits paid	(20.8)	(35.2)
Fair value of plan assets, end of year	385.9	395.7	339.9
Funded status of plans, end of year	(153.7)	(164.3)
Spire Missouri \| Postretirement Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	159.7	143.6
Actual return on plan assets	16.8	13.8
Employer contributions	10.4	14.3
Spire EnergySouth acquisition	0	0
Regular benefits paid	(12)	(12)
Fair value of plan assets, end of year	174.9	159.7	143.6
Funded status of plans, end of year	(17.6)	(48.2)
Spire Alabama \| Pension Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	100	109
Actual return on plan assets	7.7	10.7
Employer contributions	11.9	0
Spire EnergySouth acquisition	0	0
Settlement benefits paid	(18.7)	(16.6)	(12.9)
Regular benefits paid	(3)	(3.1)
Fair value of plan assets, end of year	97.9	100	109
Funded status of plans, end of year	(50.3)	(74.3)
Spire Alabama \| Postretirement Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	82.8	79.7
Actual return on plan assets	8.9	6.2
Employer contributions	0	0
Spire EnergySouth acquisition	0	0
Regular benefits paid	(5.3)	(3.1)
Fair value of plan assets, end of year	86.4	82.8	$ 79.7
Funded status of plans, end of year	$ 45.8	$ 37.4

PENSION PLANS AND OTHER POSTR88

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent liabilities	$ (237.4)	$ (303.7)
Pension Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.5)	(0.6)
Noncurrent liabilities	(216.7)	(253.6)
Total	(217.2)	(254.2)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	163	179.4
Prior service (credit) cost	(13.4)	8.2
Subtotal	149.6	187.6
Adjustments for amounts included in regulatory assets	(147.1)	(184.8)
Total	2.5	2.8
Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.4)	(0.4)
Noncurrent liabilities	(21)	(50.1)
Total	27	(12.8)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	1.5	38
Prior service (credit) cost	(6.6)	(5.2)
Subtotal	(5.1)	32.8
Adjustments for amounts included in regulatory assets	5.1	(32.8)
Total	0	0
Spire Missouri
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent liabilities	(173)	(211.8)
Spire Missouri \| Pension Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.5)	(0.6)
Noncurrent liabilities	(153.2)	(163.7)
Total	(153.7)	(164.3)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	126.2	135.5
Prior service (credit) cost	7.3	8.2
Subtotal	133.5	143.7
Adjustments for amounts included in regulatory assets	(131)	(140.9)
Total	2.5	2.8
Spire Missouri \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.4)	(0.4)
Noncurrent liabilities	(19.8)	(48.1)
Total	(17.6)	(48.2)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	12.3	43.4
Prior service (credit) cost	(3.7)	(3.4)
Subtotal	8.6	40
Adjustments for amounts included in regulatory assets	(8.6)	(40)
Total	0	0
Spire Alabama
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent liabilities	(50.2)	(74.3)
Spire Alabama \| Pension Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	0	0
Noncurrent liabilities	(50.3)	(74.3)
Total	(50.3)	(74.3)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	40.9	43.9
Prior service (credit) cost	(20.7)	0
Subtotal	20.2	43.9
Adjustments for amounts included in regulatory assets	(20.2)	(43.9)
Total	0	0
Spire Alabama \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	0	0
Noncurrent liabilities	0	0
Total	45.8	37.4
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	(9.7)	(5.4)
Prior service (credit) cost	(2.9)	(1.8)
Subtotal	(12.6)	(7.2)
Adjustments for amounts included in regulatory assets	12.6	7.2
Total	0	0
Current Asset [Member] \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	1.4	0.3
Current Asset [Member] \| Spire Missouri \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	1.4	0.3
Current Asset [Member] \| Spire Alabama \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	0	0
Noncurrent Asset [Member] \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	47	37.4
Noncurrent Asset [Member] \| Spire Missouri \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	1.2	0
Noncurrent Asset [Member] \| Spire Alabama \| Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	$ 45.8	$ 37.4

PENSION PLANS AND OTHER POSTR89

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Pre-tax Amortization from AOCI (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017USD ($)
Pension Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	$ 12.6
Amortization of prior service (credit) cost	(0.9)
Subtotal	11.7
Regulatory adjustment	(11.4)
Total	0.3
Postretirement Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	0.9
Amortization of prior service (credit) cost	(0.1)
Subtotal	0.8
Regulatory adjustment	(0.8)
Total	0
Spire Missouri \| Pension Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	10.5
Amortization of prior service (credit) cost	0.9
Subtotal	11.4
Regulatory adjustment	(11.1)
Total	0.3
Spire Missouri \| Postretirement Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	0.9
Amortization of prior service (credit) cost	0.3
Subtotal	1.2
Regulatory adjustment	(1.2)
Total	0
Spire Alabama \| Pension Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	2.1
Amortization of prior service (credit) cost	(1.8)
Subtotal	0.3
Regulatory adjustment	(0.3)
Total	0
Spire Alabama \| Postretirement Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	0
Amortization of prior service (credit) cost	(0.4)
Subtotal	(0.4)
Regulatory adjustment	0.4
Total	$ 0

PENSION PLANS AND OTHER POSTR90

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Assumptions Used to Calculate Net Periodic Cost and Benefit Obligations (Details)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Spire Alabama \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%	2.92%
Expected long-term rate of return on plan assets	7.25%	7.50%
Spire Alabama \| Pension Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.45%	4.25%	4.15%
Expected long-term rate of return on plan assets			7.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.65%	3.45%
Spire Alabama \| Pension Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.50%	4.30%	4.25%
Expected long-term rate of return on plan assets			7.25%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.70%	3.50%
Spire Alabama \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.60%	4.50%	4.40%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.80%	3.60%
Spire Alabama \| Postretirement Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	4.00%	4.50%	4.75%
Spire Alabama \| Postretirement Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	6.25%	7.25%	7.50%
Spire Missouri \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.50%	4.40%	4.30%
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Expected long-term rate of return on plan assets	7.75%	7.75%	7.75%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.75%	3.50%
Spire Missouri \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.15%	4.00%	4.15%
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.60%	3.15%
Weighted average rate of future compensation increase	3.00%	3.00%
Spire Missouri \| Postretirement Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	5.75%	6.00%	6.25%
Spire Missouri \| Postretirement Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	7.75%	7.75%	7.75%
Missouri Gas Energy (MGE) \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.50%	4.50%	4.45%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.70%	3.50%
Missouri Gas Energy (MGE) \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.45%	4.30%	4.40%
Expected long-term rate of return on plan assets	5.50%	4.75%	5.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	3.60%	3.45%
Missouri Gas Energy (MGE) \| Postretirement Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets			3.75%
Missouri Gas Energy (MGE) \| Postretirement Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets			5.75%
Laclede Gas, Alabama Gas Company, And Missouri Gas Energy \| Pension Plans
Assumptions used to calculate benefit obligations [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%

PENSION PLANS AND OTHER POSTR91

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Projected Benefit Obligation (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 748.8	$ 794.7
Accumulated benefit obligation	701.4	724.5
Fair value of plan assets	531.6	540.5
Spire Missouri
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	539.6	560
Accumulated benefit obligation	500.4	517.7
Fair value of plan assets	385.9	395.7
Spire Alabama
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	148.2	174.3
Accumulated benefit obligation	142.8	149.8
Fair value of plan assets	$ 97.9	$ 100

PENSION PLANS AND OTHER POSTR92

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Targeted and Actual Plan Assets by Category (Details)	Sep. 30, 2017	Sep. 30, 2016
Spire Alabama \| Pension Plans
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	100.00%	100.00%
Actual allocation of plan assets	100.00%	100.00%
Spire Alabama \| Pension Plans \| Equity markets
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	60.00%	60.00%
Actual allocation of plan assets	58.50%	59.20%
Spire Alabama \| Pension Plans \| Commodity Contract [Member]
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	29.00%	29.00%
Actual allocation of plan assets	28.70%	28.80%
Spire Alabama \| Pension Plans \| Real Estate [Member]
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	11.00%	11.00%
Actual allocation of plan assets	12.80%	12.00%
Spire Alabama \| Postretirement Plans
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	100.00%
Actual allocation of plan assets	100.00%	100.00%
Spire Alabama \| Postretirement Plans \| Equity markets
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	60.00%
Actual allocation of plan assets	60.10%	60.50%
Spire Alabama \| Postretirement Plans \| Debt securities
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	40.00%
Actual allocation of plan assets	39.90%	39.50%
Spire Missouri \| Pension Plans
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	100.00%	100.00%
Actual allocation of plan assets	100.00%	100.00%
Spire Missouri \| Pension Plans \| Equity markets
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	56.40%	56.20%
Actual allocation of plan assets	56.80%	56.90%
Spire Missouri \| Pension Plans \| Debt securities
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	43.60%	43.80%
Actual allocation of plan assets	42.00%	43.10%
Spire Missouri \| Pension Plans \| Other
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	0.00%	0.00%
Actual allocation of plan assets	1.20%	0.00%
Spire Missouri \| Postretirement Plans
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	100.00%
Actual allocation of plan assets	100.00%	100.00%
Spire Missouri \| Postretirement Plans \| Equity markets
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	60.00%
Actual allocation of plan assets	59.00%	59.10%
Spire Missouri \| Postretirement Plans \| Debt securities
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	40.00%
Actual allocation of plan assets	39.40%	39.40%
Spire Missouri \| Postretirement Plans \| Other
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	0.00%
Actual allocation of plan assets	1.60%	1.50%

PENSION PLANS AND OTHER POSTR93

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Expected Future Benefit Payments (Details) $ in Millions	Sep. 30, 2017USD ($)
Pension Plans
Expected benefit payments [Abstract]
2,017	$ 63.5
2,018	63.2
2,019	63.2
2,020	58.1
2,021	57.9
2022 - 2026	281.1
Postretirement Plans
Expected benefit payments [Abstract]
2,017	15
2,018	16
2,019	17.1
2,020	18.3
2,021	18.9
2022 - 2026	101.3
Spire Missouri \| Pension Plans
Expected benefit payments [Abstract]
2,017	50.7
2,018	49.5
2,019	49.1
2,020	43.5
2,021	42.1
2022 - 2026	198.1
Spire Missouri \| Postretirement Plans
Expected benefit payments [Abstract]
2,017	11.8
2,018	12.8
2,019	14
2,020	15.2
2,021	15.9
2022 - 2026	86.5
Spire Alabama \| Pension Plans
Expected benefit payments [Abstract]
2,017	10.3
2,018	11.1
2,019	11.5
2,020	11.9
2,021	13
2022 - 2026	67.8
Spire Alabama \| Postretirement Plans
Expected benefit payments [Abstract]
2,017	2.8
2,018	2.8
2,019	2.8
2,020	2.8
2,021	2.7
2022 - 2026	$ 13

PENSION PLANS AND OTHER POSTR94

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Assumed Medical Cost Trend Rates and Effect of 1% Changed (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate)	5.00%	5.00%
Year the rate reaches the ultimate trend	2,023	2,023
Assumed 1% change in the assumed medical cost trend rate [Abstract]
Effect of 1% increase on net periodic postretirement benefit cost	$ 1.7
Effect of 1% decrease on net periodic postretirement benefit cost	(1.4)
Effect of 1% increase on accumulated postretirement benefit obligation	10
Effect of 1% decrease on accumulated postretirement benefit obligation	$ (9.2)
Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Medical cost trend assumed for next year	7.25%	7.50%
Assumed 1% change in the assumed medical cost trend rate [Abstract]
Effect of 1% increase on net periodic postretirement benefit cost	$ 1.6
Effect of 1% decrease on net periodic postretirement benefit cost	(1.3)
Effect of 1% increase on accumulated postretirement benefit obligation	8
Effect of 1% decrease on accumulated postretirement benefit obligation	$ (7.4)
Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Medical cost trend assumed for next year	7.25%	7.50%
Assumed 1% change in the assumed medical cost trend rate [Abstract]
Effect of 1% increase on net periodic postretirement benefit cost	$ 0.1
Effect of 1% decrease on net periodic postretirement benefit cost	(0.1)
Effect of 1% increase on accumulated postretirement benefit obligation	1.4
Effect of 1% decrease on accumulated postretirement benefit obligation	$ (1.3)

PENSION PLANS AND OTHER POSTR95

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Fair Value Measurements of Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	$ 531.6	$ 540.5	$ 448.9
Pension Plans \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.3	51.2
Pension Plans \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	67.5	126.1
Pension Plans \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	48.6
Pension Plans \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	102.9	149
Pension Plans \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.7	45.1
Pension Plans \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	183.7	137.4
Pension Plans \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.2	6.3
Pension Plans \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	52.3	25.3
Pension Plans \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(2.6)	0.1
Pension Plans \| Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	414.8	383.6
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.3	51.2
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	42.1	99.3
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.4
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	34.4	23
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	33.2	42.1
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	183.7	137.4
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.2	6.3
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	45.1	25.3
Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(2.6)	(1)
Pension Plans \| Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	116.8	156.8
Pension Plans \| Significant Observable Inputs (Level 2) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	25.4	26.7
Pension Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	11.2
Pension Plans \| Significant Observable Inputs (Level 2) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	68.5	126
Pension Plans \| Significant Observable Inputs (Level 2) \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.5	3
Pension Plans \| Significant Observable Inputs (Level 2) \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Observable Inputs (Level 2) \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Observable Inputs (Level 2) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	7.2	0
Pension Plans \| Significant Observable Inputs (Level 2) \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	1.1
Pension Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0.1
Pension Plans \| Significant Unobservable Inputs (Level 3) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0.1
Pension Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Pension Plans \| Significant Unobservable Inputs (Level 3) \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	265.5	246.4	223.3
Postretirement Plans \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4	4.8
Postretirement Plans \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	245.8	226.4
Postretirement Plans \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	15.7	15.2
Postretirement Plans \| Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	179.1	163.6
Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4	4.8
Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	174.1	157.9
Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	1	0.9
Postretirement Plans \| Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	86.4	82.8
Postretirement Plans \| Significant Observable Inputs (Level 2) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Postretirement Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	71.7	68.5
Postretirement Plans \| Significant Observable Inputs (Level 2) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	14.7	14.3
Postretirement Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	385.9	395.7	339.9
Spire Missouri \| Pension Plans \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	31.7	46.5
Spire Missouri \| Pension Plans \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	11.9	14.9
Spire Missouri \| Pension Plans \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	5.7
Spire Missouri \| Pension Plans \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	68.5	120.2
Spire Missouri \| Pension Plans \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.7	45.1
Spire Missouri \| Pension Plans \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	183.7	137.4
Spire Missouri \| Pension Plans \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.2	6.3
Spire Missouri \| Pension Plans \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	45.1	25.2
Spire Missouri \| Pension Plans \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets		0.1
Spire Missouri \| Pension Plans \| Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(2.6)
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	295.3	256.5
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	31.7	46.5
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	33.2	42.1
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	183.7	137.4
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.2	6.3
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	45.1	25.2
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets		(1)
Spire Missouri \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(2.6)
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	90.6	139.1
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	11.9	14.8
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	5.7
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	68.5	120.2
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.5	3
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets		1.1
Spire Missouri \| Pension Plans \| Significant Observable Inputs (Level 2) \| Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0.1
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0.1
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| US government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| US corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| US municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Derivative instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets		0
Spire Missouri \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Missouri \| Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	174.9	159.7	143.6
Spire Missouri \| Postretirement Plans \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.9	4.6
Spire Missouri \| Postretirement Plans \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	171	155.1
Spire Missouri \| Postretirement Plans \| Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	174.9	159.7
Spire Missouri \| Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.9	4.6
Spire Missouri \| Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	171	155.1
Spire Missouri \| Postretirement Plans \| Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Postretirement Plans \| Significant Observable Inputs (Level 2) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Postretirement Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Postretirement Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Missouri \| Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	97.9	100	109
Spire Alabama \| Pension Plans \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.4	0.4
Spire Alabama \| Pension Plans \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.5	70.9
Spire Alabama \| Pension Plans \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	28.9
Spire Alabama \| Pension Plans \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	23.2	28.7
Spire Alabama \| Pension Plans \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.9
Spire Alabama \| Pension Plans \| Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	80.2	82.4
Spire Alabama \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.4	0.4
Spire Alabama \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	28.4	59
Spire Alabama \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	25.2
Spire Alabama \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	23.2	23
Spire Alabama \| Pension Plans \| Quoted Prices in Active Markets (Level 1) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Alabama \| Pension Plans \| Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	17.7	17.6
Spire Alabama \| Pension Plans \| Significant Observable Inputs (Level 2) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Pension Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	9.1	11.9
Spire Alabama \| Pension Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.7
Spire Alabama \| Pension Plans \| Significant Observable Inputs (Level 2) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	5.7
Spire Alabama \| Pension Plans \| Significant Observable Inputs (Level 2) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.9
Spire Alabama \| Pension Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - international
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Alabama \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| US bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Pension Plans \| Significant Unobservable Inputs (Level 3) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Spire Alabama \| Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	86.4	82.8	$ 79.7
Spire Alabama \| Postretirement Plans \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	71.7	68.5
Spire Alabama \| Postretirement Plans \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	14.7	14.3
Spire Alabama \| Postretirement Plans \| Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Postretirement Plans \| Quoted Prices in Active Markets (Level 1) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Postretirement Plans \| Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	86.4	82.8
Spire Alabama \| Postretirement Plans \| Significant Observable Inputs (Level 2) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	71.7	68.5
Spire Alabama \| Postretirement Plans \| Significant Observable Inputs (Level 2) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	14.7	14.3
Spire Alabama \| Postretirement Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| Equity mutual funds - domestic
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama \| Postretirement Plans \| Significant Unobservable Inputs (Level 3) \| International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	$ 0	$ 0

INFORMATION BY OPERATING SEGM96

INFORMATION BY OPERATING SEGMENT - Schedule of Operating Segment Information (Details) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2017USD ($)operating_segment	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of operating segments \| operating_segment									2
Operating Segment Information [Abstract]
Total Operating Revenues	$ 258.7	$ 323.5	$ 663.4	$ 495.1	$ 279.3	$ 249.3	$ 609.3	$ 399.4	$ 1,740.7	$ 1,537.3	$ 1,976.4
Gas Utility
Natural and propane gas									570.5	492.2	882.4
Other operation and maintenance expenses									405	377.5	390.6
Depreciation and amortization									153.5	136.9	129.9
Taxes, other than income taxes									137.8	125.2	142.1
Total Gas Utility Operating Expenses									1,266.8	1,131.8	1,545
Gas Marketing and other									152.2	123.2	158.9
Total Operating Expenses									1,419	1,255	1,703.9
Operating Income	1.9	$ 50.3	$ 180.4	$ 89.1	(7.7)	$ 35.3	$ 167.7	$ 87	321.7	282.3	272.5
Net Economic Earnings									167.6	149.1	138.3
Capital Expenditures									438.1	293.3	289.8
ASSETS
Total Assets	6,546.7				6,064.4				6,546.7	6,064.4	5,277.6
Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									(14.2)	(5.4)	(76.5)
Gas Utility
Natural and propane gas									(75.4)	(47.5)	(75.2)
Other operation and maintenance expenses									(4.1)	(1.8)	(1)
Depreciation and amortization									0	0	0
Taxes, other than income taxes									0	0	0
Total Gas Utility Operating Expenses									(79.5)	(49.3)	(76.2)
Gas Marketing and other									65.3	43.9	(0.3)
Total Operating Expenses									(14.2)	(5.4)	(76.5)
Operating Income									0	0	0
Net Economic Earnings									0	0	0
Capital Expenditures									0	0	0
ASSETS
Total Assets	(1,490.2)				(1,161.9)				(1,490.2)	(1,161.9)	(1,116.8)
Other
Operating Segment Information [Abstract]
Total Operating Revenues									1.4	1.6	1.7
Gas Utility
Depreciation and amortization expense									0.5	0.5	0.6
ASSETS
Total Assets	2,239.5				1,836.6				2,239.5	1,836.6	1,554.5
Corporate Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									6.3	3.2	2
Corporate And Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									7.7	4.8	3.7
Gas Utility
Natural and propane gas									0	0	0
Other operation and maintenance expenses									0	0	0
Depreciation and amortization									0	0	0
Taxes, other than income taxes									0	0	0
Total Gas Utility Operating Expenses									0	0	0
Gas Marketing and other									12.8	12.6	12.6
Total Operating Expenses									12.8	12.6	12.6
Operating Income									(5.1)	(7.8)	(8.9)
Net Economic Earnings									(20.7)	(17.6)	(16.3)
Capital Expenditures									25.5	1.6	5.4
Gas Utility:
Operating Segment Information [Abstract]
Total Operating Revenues									1,660	1,457.2	1,891.8
Gas Utility: \| Operating Segments
Operating Segment Information [Abstract]
Total Operating Revenues									1,667.9	1,459.4	1,895.8
Gas Utility
Natural and propane gas									645.9	539.7	957.6
Other operation and maintenance expenses									409.1	379.3	391.6
Depreciation and amortization									153.5	136.9	129.9
Taxes, other than income taxes									137.8	125.2	142.1
Total Gas Utility Operating Expenses									1,346.3	1,181.1	1,621.2
Gas Marketing and other									0	0	0
Total Operating Expenses									1,346.3	1,181.1	1,621.2
Operating Income									321.6	278.3	274.6
Net Economic Earnings									181.5	160.3	150.4
Capital Expenditures									412.6	291.7	284.4
ASSETS
Total Assets	5,551.2				5,184.7				5,551.2	5,184.7	4,679.3
Gas Utility: \| Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									7.9	2.2	4
Gas Marketing:
Operating Segment Information [Abstract]
Total Operating Revenues									79.3	78.5	82.9
Gas Marketing: \| Operating Segments
Operating Segment Information [Abstract]
Total Operating Revenues									79.3	78.5	153.4
Gas Utility
Natural and propane gas									0	0	0
Other operation and maintenance expenses									0	0	0
Depreciation and amortization									0	0	0
Taxes, other than income taxes									0	0	0
Total Gas Utility Operating Expenses									0	0	0
Gas Marketing and other									74.1	66.7	146.6
Total Operating Expenses									74.1	66.7	146.6
Operating Income									5.2	11.8	6.8
Net Economic Earnings									6.8	6.4	4.2
Capital Expenditures									0	0	0
Depreciation and amortization expense									0.1	0.1	0.3
ASSETS
Total Assets	$ 246.2				$ 205				246.2	205	160.6
Gas Marketing: \| Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									$ 0	$ 0	$ 70.5

INFORMATION BY OPERATING SEGM97

INFORMATION BY OPERATING SEGMENT - Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting [Abstract]
Net Income	$ (13.3)	$ 21.7	$ 108	$ 45.2	$ (14.2)	$ 10.7	$ 100.8	$ 46.9	$ 161.6	$ 144.2	$ 136.9
Unrealized loss (gain) on energy-related derivatives									6	(0.1)	(2.8)
Lower of cost or market inventory adjustments									0	0.2	0.4
Realized (gain) loss on economic hedges prior to the sale of the physical commodity									(0.3)	(1.6)	2.4
Acquisition, divestiture and restructuring activities									4	9.2	9.8
Gain on sale of property									0	0	(7.6)
Income tax effect of adjustments									(3.7)	(2.8)	(0.8)
Net Economic Earnings									$ 167.6	$ 149.1	$ 138.3

REGULATORY MATTERS - Schedule

REGULATORY MATTERS - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Regulatory Assets [Line Items]
Regulatory assets, current	$ 175.5	$ 93.9
Regulatory assets, non current	791.1	838
Total Regulatory Assets	966.6	931.9
Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets, current	42.2	27
Regulatory assets, non current	404.7	487.9
Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, current	102.6	49.7
Future income taxes due from customers
Regulatory Assets [Line Items]
Regulatory assets, non current	170.5	151.3
Accrued cost of removal
Regulatory Assets [Line Items]
Regulatory assets, non current	123.3	130.6
Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, non current	9.9	12.6
Energy efficiency
Regulatory Assets [Line Items]
Regulatory assets, non current	29	25.5
Other
Regulatory Assets [Line Items]
Regulatory assets, current	30.7	17.2
Regulatory assets, non current	53.7	30.1
Spire Missouri
Regulatory Assets [Line Items]
Regulatory assets, current	95.6	67
Regulatory assets, non current	557.8	589.8
Total Regulatory Assets	653.4	656.8
Spire Missouri \| Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets, current	34.9	20.2
Regulatory assets, non current	322.7	375.7
Spire Missouri \| Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, current	57.4	43.1
Spire Missouri \| Future income taxes due from customers
Regulatory Assets [Line Items]
Regulatory assets, non current	170.5	151.3
Spire Missouri \| Accrued cost of removal
Regulatory Assets [Line Items]
Regulatory assets, non current	0	0
Spire Missouri \| Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, non current	9.9	12.6
Spire Missouri \| Energy efficiency
Regulatory Assets [Line Items]
Regulatory assets, non current	29	25.5
Spire Missouri \| Other
Regulatory Assets [Line Items]
Regulatory assets, current	3.3	3.7
Regulatory assets, non current	25.7	24.7
Spire Alabama
Regulatory Assets [Line Items]
Regulatory assets, current	64.6	20.5
Regulatory assets, non current	197	230.7
Total Regulatory Assets	261.6	251.2
Spire Alabama \| Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets, current	7.2	6.8
Regulatory assets, non current	72.6	98.9
Spire Alabama \| Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, current	45.2	5.6
Spire Alabama \| Future income taxes due from customers
Regulatory Assets [Line Items]
Regulatory assets, non current	0	0
Spire Alabama \| Accrued cost of removal
Regulatory Assets [Line Items]
Regulatory assets, non current	123.3	130.6
Spire Alabama \| Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, non current	0	0
Spire Alabama \| Energy efficiency
Regulatory Assets [Line Items]
Regulatory assets, non current	0	0
Spire Alabama \| Other
Regulatory Assets [Line Items]
Regulatory assets, current	12.2	8.1
Regulatory assets, non current	$ 1.1	$ 1.2

REGULATORY MATTERS - Schedule o

REGULATORY MATTERS - Schedule of Regulatory Assets Not Earnings a Return (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	$ 380.3	$ 404.8
Future income taxes due from customers
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	170.5	151.3
Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	198.5	240.6
Other
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	11.3	12.9
Spire Missouri
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	380.3	404.8
Spire Missouri \| Future income taxes due from customers
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	170.5	151.3
Spire Missouri \| Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	198.5	240.6
Spire Missouri \| Other
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	$ 11.3	$ 12.9

REGULATORY MATTERS - Narrative

REGULATORY MATTERS - Narrative (Details) - USD ($)	Sep. 30, 2017	Jul. 31, 2017	Apr. 30, 2017	Apr. 11, 2017	Apr. 04, 2017	Feb. 03, 2017	Jan. 31, 2017	Jan. 18, 2017	Nov. 30, 2016	Nov. 29, 2016	Sep. 30, 2016	Jul. 31, 2016	Jan. 01, 2014	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2018	Sep. 18, 2017	May 30, 2017	Apr. 15, 2016	Feb. 10, 2016	Dec. 01, 2015
Public Utilities, General Disclosures [Line Items]
Remaining Recovery Period of Certain Regulatory Assets for which No Return on Investment During Recovery Period is Provided															20 years
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided															15 years
Total Current Regulatory Liabilities	$ 22,600,000										$ 30,600,000			$ 22,600,000	$ 22,600,000	$ 30,600,000
Regulatory Liabilities	179,800,000										161,300,000			179,800,000	179,800,000	161,300,000
Spire Missouri
Public Utilities, General Disclosures [Line Items]
Regulatory preferred stock and debt securities issuance, amount requested				$ 25,500,000																	$ 550,000,000
Regulatory preferred stock and debt securities issuance, amount authorized	300,000,000													300,000,000	300,000,000					$ 300,000,000		$ 300,000,000
Approved return rate on equity				10.35%
Total Current Regulatory Liabilities	2,700,000										1,300,000			2,700,000	2,700,000	1,300,000
Regulatory Liabilities	83,900,000										68,600,000			83,900,000	83,900,000	68,600,000
Missouri Gas Energy (MGE)
Public Utilities, General Disclosures [Line Items]
Regulatory preferred stock and debt securities issuance, amount requested				$ 34,000,000
Approved return rate on equity				10.35%
Spire Alabama
Public Utilities, General Disclosures [Line Items]
Regulatory preferred stock and debt securities issuance, amount authorized	75,000,000													75,000,000	75,000,000
Total Current Regulatory Liabilities	12,000,000										22,700,000			12,000,000	12,000,000	22,700,000
Regulatory Liabilities	51,600,000										64,400,000			51,600,000	$ 51,600,000	64,400,000
Potential Performance-Based Adjustment, Percent															0.05%
Spire Alabama \| Line of Credit
Public Utilities, General Disclosures [Line Items]
Line of credit facility borrowing capacity	200,000,000													200,000,000	$ 200,000,000
Line of Credit Facility, Maximum Amount Outstanding During Period														$ 25,000,000
APSC \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount	$ 2,700,000	$ 0	$ 0				$ 0		$ 2,500,000		2,700,000	$ 4,800,000			$ 10,700,000	7,800,000	$ 4,700,000
Rate increase (decrease), margin of index range	1.75%													1.75%	1.75%
Bond purchase agreement amount																			$ 75,000,000
Approved return rate on equity													10.80%
Maximum return on equity, percentage of prior year revenues																							4.00%
Infrastructure System Replacement Surcharge \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Approved rate increase, annualized revenue				$ 32,600,000
Regulatory preferred stock and debt securities issuance, amount requested				58,100,000
Infrastructure System Replacement Surcharge \| Missouri Gas Energy (MGE)
Public Utilities, General Disclosures [Line Items]
Approved rate increase, annualized revenue				16,400,000
Regulatory preferred stock and debt securities issuance, amount requested				$ 50,400,000
Infrastructure System Replacement Surcharge \| MoPSC \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Requested rate increase						$ 3,300,000					5,000,000
Approved rate increase, annualized revenue								$ 4,500,000
Approved rate increase (decrease) amount					$ 32,600,000			29,500,000
Infrastructure System Replacement Surcharge \| MoPSC \| Missouri Gas Energy (MGE)
Public Utilities, General Disclosures [Line Items]
Requested rate increase						$ 2,900,000					3,400,000
Recommended rate increase (decrease) amount					3,000,000					$ 3,400,000
Approved rate increase, annualized revenue								3,200,000
Approved rate increase (decrease) amount					16,400,000			$ 13,400,000
Updated filings \| MoPSC \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Recommended rate increase (decrease) amount					$ 3,000,000					$ 4,500,000
Bond purchase agreement \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Bond purchase agreement amount																				$ 170,000,000
Minimum \| APSC \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity													10.50%
Maximum \| APSC \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity													10.95%
Amount subject to refund
Public Utilities, General Disclosures [Line Items]
Total Current Regulatory Liabilities	$ 8,200,000										9,300,000			$ 8,200,000	$ 8,200,000	9,300,000
Amount subject to refund \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Total Current Regulatory Liabilities	0										0			0	0	0
Amount subject to refund \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Total Current Regulatory Liabilities	8,200,000										$ 9,300,000			8,200,000	8,200,000	$ 9,300,000
Amount subject to refund \| APSC \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Total Current Regulatory Liabilities	6,300,000													6,300,000	6,300,000
Regulatory Liabilities	$ 12,300,000													$ 12,300,000	$ 12,300,000
Scenario, Forecast \| Amount subject to refund \| APSC \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Total Current Regulatory Liabilities																		$ 8,200,000

REGULATORY MATTERS - Schedul101

REGULATORY MATTERS - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	$ 22.6	$ 30.6
Total Noncurrent Regulatory Liabilities	157.2	130.7
Total Regulatory Liabilities	179.8	161.3
RSE adjustment
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	1.4	7.5
Pension and postretirement costs
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	8.2	9.3
Total Noncurrent Regulatory Liabilities	4.1	9.4
Unbilled service margin
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	5.9
Unamortized purchased gas adjustments
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	1	1.7
Other
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	12	6.2
Total Noncurrent Regulatory Liabilities	37.1	17.6
Pension and postretirement benefit costs
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	32.2	28.9
Accrued cost of removal
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	83.8	74.8
Spire Missouri
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	2.7	1.3
Total Noncurrent Regulatory Liabilities	81.2	67.3
Total Regulatory Liabilities	83.9	68.6
Spire Missouri \| RSE adjustment
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Spire Missouri \| Pension and postretirement costs
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Total Noncurrent Regulatory Liabilities	0	0
Spire Missouri \| Unbilled service margin
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Spire Missouri \| Unamortized purchased gas adjustments
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Spire Missouri \| Other
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	2.7	1.3
Total Noncurrent Regulatory Liabilities	26.7	12.2
Spire Missouri \| Pension and postretirement benefit costs
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	0	0
Spire Missouri \| Accrued cost of removal
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	54.5	55.1
Spire Alabama
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	12	22.7
Total Noncurrent Regulatory Liabilities	39.6	41.7
Total Regulatory Liabilities	51.6	64.4
Spire Alabama \| RSE adjustment
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	1.4	5
Spire Alabama \| Pension and postretirement costs
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	8.2	9.3
Total Noncurrent Regulatory Liabilities	4.1	9.4
Spire Alabama \| Unbilled service margin
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	5.9
Spire Alabama \| Unamortized purchased gas adjustments
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Spire Alabama \| Other
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	2.4	2.5
Total Noncurrent Regulatory Liabilities	3.3	3.4
Spire Alabama \| Pension and postretirement benefit costs
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	32.2	28.9
Spire Alabama \| Accrued cost of removal
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	$ 0	$ 0

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Commitments (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017USD ($)
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	$ 1,281.8
Spire Missouri
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	563.9
Spire Missouri \| Purchase Commitment \| Subsidiary of Common Parent
Long-term Purchase Commitment [Line Items]
Annual purchase commitment	$ 1
Commitment termination minimum required notification period	6 months
Spire Alabama
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	$ 285.6

COMMITMENTS AND CONTINGENCIE103

COMMITMENTS AND CONTINGENCIES - Leases and Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Loss Contingencies [Line Items]
Aggregate rental expense	$ 9.7	$ 11.9	$ 14.1
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum rental commitments - in fiscal year 2017	10.1
Minimum rental commitments - due in fiscal year 2018	9.3
Minimum rental commitments - due in fiscal year 2019	7.8
Minimum rental commitments - due in fiscal year 2020	6.1
Minimum rental commitments - due in fiscal year 2021	6
Minimum rental commitments - due later	44.4
Minimum rental commitments - total	83.7
Sublease rentals	2.1	2.1	0.2
Minimum future sublease rentals to be received - fiscal year 2017	2.1
Minimum future sublease rentals to be received - fiscal year 2018	2.1
Minimum future sublease rentals to be received - fiscal year 2019	2.1
Minimum future sublease rentals to be received - fiscal year 2020	0.5
Outstanding mortgage loans incurred in connection with various real estate ventures with general partners	1.3
Spire Missouri
Loss Contingencies [Line Items]
Aggregate rental expense	4.8	4.3	7.6
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum rental commitments - in fiscal year 2017	2.1
Minimum rental commitments - due in fiscal year 2018	1.3
Minimum rental commitments - due in fiscal year 2019	0.2
Minimum rental commitments - due in fiscal year 2020	0.2
Minimum rental commitments - due in fiscal year 2021	0
Minimum rental commitments - due later	0
Minimum rental commitments - total	3.8
Spire Alabama
Loss Contingencies [Line Items]
Aggregate rental expense	4.6	3.7	4
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum rental commitments - in fiscal year 2017	4
Minimum rental commitments - due in fiscal year 2018	4.1
Minimum rental commitments - due in fiscal year 2019	3.8
Minimum rental commitments - due in fiscal year 2020	2.1
Minimum rental commitments - due in fiscal year 2021	2.1
Minimum rental commitments - due later	2.8
Minimum rental commitments - total	18.9
Sublease rentals	2.1	$ 2.1	$ 2.1
Minimum future sublease rentals to be received - fiscal year 2018	2.1
Minimum future sublease rentals to be received - fiscal year 2019	2.1
Minimum future sublease rentals to be received - fiscal year 2020	$ 0.5

COMMITMENTS AND CONTINGENCIE104

COMMITMENTS AND CONTINGENCIES - Contingencies (Details)	Dec. 17, 2013fatality	Sep. 30, 2017plaintiffsitelawsuit	Sep. 30, 2016lawsuit	Sep. 30, 2015site
Site Contingency [Line Items]
Number of incident fatalities \| fatality	1
Spire Missouri
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP) sites in Shrewsbury, Missouri		1
Number of former manufactured gas plant (MGP) sites in the City of St. Louis		2
Spire Missouri \| Previous Ownership
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)				19
Missouri Gas Energy (MGE) \| Previous Ownership
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)		7
Spire Alabama
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)		9
Number of former manufactured gas distribution		5
Spire Alabama \| Current Ownership
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)		4
Number of former manufactured gas distribution		1
Mobile Gas
Site Contingency [Line Items]
Number of lawsuits \| lawsuit			14
Number of lawsuits settled \| lawsuit			11
Number of lawsuits pending \| lawsuit		3
Mobile Gas \| Pending Litigation
Site Contingency [Line Items]
Number of plaintiffs \| plaintiff		270
Mobile Gas \| Previous Ownership
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)				1

INTERIM FINANCIAL INFORMATIO105

INTERIM FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Quarterly Financial Information [Line Items]
Total Operating Revenues	$ 258.7	$ 323.5	$ 663.4	$ 495.1	$ 279.3	$ 249.3	$ 609.3	$ 399.4	$ 1,740.7	$ 1,537.3	$ 1,976.4
Operating Income	1.9	50.3	180.4	89.1	(7.7)	35.3	167.7	87	321.7	282.3	272.5
Net Income (Loss)	$ (13.3)	$ 21.7	$ 108	$ 45.2	$ (14.2)	$ 10.7	$ 100.8	$ 46.9	$ 161.6	$ 144.2	$ 136.9
Basic Earnings Per Share of Common Stock (in dollars per share)	$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ (0.31)	$ 0.24	$ 2.32	$ 1.08	$ 3.44	$ 3.26	$ 3.16
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ (0.31)	$ 0.24	$ 2.31	$ 1.08	$ 3.43	$ 3.24	$ 3.16
Spire Missouri
Quarterly Financial Information [Line Items]
Total Operating Revenues	$ 162.6	$ 198.5	$ 447.2	$ 363.6	$ 144.3	$ 179.3	$ 446.7	$ 317.2	$ 1,171.9	$ 1,087.5	$ 1,416.6
Operating Income	11.7	30.5	90.2	64.5	5.4	29.4	87	65.1	196.9	186.9	185.4
Net Income (Loss)	2.5	15.5	57	38	(1.7)	13.9	54.3	39.4	113	105.9	105.3
Spire Alabama
Quarterly Financial Information [Line Items]
Total Operating Revenues	64.5	90.5	158.8	86.7	46.2	74	166	82.3	400.5	368.5	479.2
Operating Income	(8.4)	15.5	78.9	19.8	(17.1)	9.3	80.4	18.9	105.8	91.5	89.2
Net Income (Loss)	$ (7.2)	$ 7.4	$ 47.6	$ 10.3	$ (8.8)	$ 4	$ 48.1	$ 9.9	$ 58.1	$ 53.2	$ 48

Uncategorized Items - lg-201709

Label	Element	Value
Spire Alabama Inc [Member]
Dividends, Common Stock, Cash	us-gaap_DividendsCommonStockCash	$ 31,500,000
Retained Earnings [Member]
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	0
Retained Earnings [Member] \| Spire Alabama Inc [Member]
Dividends, Common Stock, Cash	us-gaap_DividendsCommonStockCash	$ 31,500,000