Spire Missouri 10-K 15 Nov 18 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2018	Nov. 12, 2018	Mar. 31, 2018
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			$ 3,391,208,752
Entity Emerging Growth	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		50,676,192
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
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 Emerging Growth	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		24,577
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
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 Emerging Growth	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		1,972,052
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Operating Revenues:
Gas Utility	$ 1,888	$ 1,660	$ 1,457.2
Gas Marketing and other	77	80.7	80.1
Total Operating Revenues	1,965	1,740.7	1,537.3
Gas Utility
Natural and propane gas	770.1	570.5	492.2
Other operation and maintenance expenses	455.6	405	377.5
Depreciation and amortization	167	153.5	136.9
Taxes, other than income taxes	152.5	137.8	125.2
Total Gas Utility Operating Expenses	1,545.2	1,266.8	1,131.8
Gas Marketing and other	140.1	152.2	123.2
Total Operating Expenses	1,685.3	1,419	1,255
Operating Income	279.7	321.7	282.3
Other Income, Net	6.4	6.6	8.6
Interest Charges:
Interest on long-term debt	83	76.8	67.6
Other interest charges	15.4	12.3	9.6
Total Interest Charges	98.4	89.1	77.2
Income Before Income Taxes	187.7	239.2	213.7
Income Tax (Benefit) Expense	(26.5)	77.6	69.5
Net Income	214.2	161.6	144.2
Net Income	214.2	161.6	153.9
Other comprehensive income (loss)	2.5	7.4	(2.2)
Comprehensive Income	$ 216.7	$ 169	$ 142
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	49.1	46.9	44.1
Diluted (in shares)	49.3	47	44.3
Basic Earnings Per Share of Common Stock (in dollars per share)	$ 4.35	$ 3.44	$ 3.26
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ 4.33	$ 3.43	$ 3.24
Spire Missouri
Operating Revenues:
Gas Utility	$ 1,285.6	$ 1,171.9	$ 1,087.5
Total Operating Revenues	1,285.6	1,171.9	1,087.5
Gas Utility
Natural and propane gas	636.8	538.3	471.3
Other operation and maintenance expenses	296.3	243.8	244.4
Depreciation and amortization	102.8	93.1	88.6
Taxes, other than income taxes	108.4	99.8	96.3
Total Operating Expenses	1,144.3	975	900.6
Operating Income	141.3	196.9	186.9
Other Income, Net	1.8	2.7	1.8
Interest Charges:
Interest on long-term debt	38.7	32.9	32.9
Other interest charges	7.7	6.2	4.5
Total Interest Charges	46.4	39.1	37.4
Income Before Income Taxes	96.7	160.5	151.3
Income Tax (Benefit) Expense	(32.6)	47.5	45.4
Net Income	129.3	113	105.9
Other comprehensive income (loss)	0.4	0.1	(0.1)
Comprehensive Income	129.7	113.1	105.8
Spire Alabama
Operating Revenues:
Gas Utility	500.7	400.5	368.5
Total Operating Revenues	500.7	400.5	368.5
Gas Utility
Natural and propane gas	176	84.5	67.3
Other operation and maintenance expenses	136.8	130.4	133.5
Depreciation and amortization	53.2	49.9	47.8
Taxes, other than income taxes	36.1	29.9	28.4
Total Operating Expenses	402.1	294.7	277
Operating Income	98.6	105.8	91.5
Other Income, Net	1.6	2.5	7.9
Interest Charges:
Interest on long-term debt	13.5	11.2	11.4
Other interest charges	3.8	3.2	2.4
Total Interest Charges	17.3	14.4	13.8
Income Before Income Taxes	82.9	93.9	85.6
Income Tax (Benefit) Expense	81.6	35.8	32.4
Net Income	$ 1.3	$ 58.1	$ 53.2

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Net income	$ 214.2	$ 161.6	$ 144.2
Net Income	214.2	161.6	153.9
Cash flow hedging derivative instruments:
Net hedging gain (loss) arising during the period	3.9	11.5	(4)
Reclassification adjustment for (income) loss included in net income	(1.5)	0	1.1
Net unrealized gain (loss) on cash flow hedging derivative instruments	2.4	11.5	(2.9)
Defined benefit pension and other postretirement benefit plans:
Amortization of actuarial loss (gain) included in net periodic pension and postretirement benefit cost	0.4	0.4	(0.3)
Net defined benefit pension and other postretirement benefit plans	0.4	0.4	(0.3)
Net unrealized gain (loss) on available-for-sale debt securities	0.3	(0.1)	0
Other Comprehensive Income (Loss), Before Tax	3.1	11.8	(3.2)
Income Tax Expense (Benefit) Related to Items of Other Comprehensive Income (Loss)	0.6	4.4	(1)
Other Comprehensive Income (Loss), Net of Tax	2.5	7.4	(2.2)
Comprehensive Income	216.7	169	142
Spire Missouri
Net income	129.3	113	105.9
Cash flow hedging derivative instruments:
Net hedging gain (loss) arising during the period	0	0.1	0
Reclassification adjustment for (income) loss included in net income	(0.1)	(0.2)	0.5
Net unrealized gain (loss) on cash flow hedging derivative instruments	(0.1)	(0.1)	0.5
Defined benefit pension and other postretirement benefit plans:
Net actuarial gain arising during the period	0	0	0
Amortization of actuarial loss (gain) included in net periodic pension and postretirement benefit cost	0.4	0.3	(0.3)
Net defined benefit pension and other postretirement benefit plans	0.4	0.3	(0.3)
Net unrealized gain (loss) on available-for-sale debt securities	0.2	(0.1)	(0.1)
Other Comprehensive Income (Loss), Before Tax	0.5	0.1	0.1
Income Tax Expense (Benefit) Related to Items of Other Comprehensive Income (Loss)	0.1	0	0.2
Other Comprehensive Income (Loss), Net of Tax	0.4	0.1	(0.1)
Comprehensive Income	$ 129.7	$ 113.1	$ 105.8

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
ASSETS
Utility Plant	$ 5,653.3	$ 5,278.4
Less: Accumulated depreciation and amortization	1,682.8	1,613.2
Net Utility Plant	3,970.5	3,665.2
Non-utility property (net of accumulated depreciation and amortization, $10.4 and $8.6 at September 30, 2018 and 2017, respectively)	174.5	52
Goodwill	1,171.6	1,171.6
Other investments	68.7	64.2
Other Property and Investments	1,414.8	1,287.8
Current Assets:
Cash and cash equivalents	4.4	7.4
Accounts receivable:
Utility	151.9	140.5
Other	167.3	149.2
Allowance for doubtful accounts	(22.4)	(18.3)
Delayed customer billings	6.9	3.4
Inventories:
Natural gas	175.2	194.9
Propane gas	12	12
Materials and supplies	23.1	18.9
Natural gas receivable	1.8	1.9
Derivative instrument assets	13.3	5.9
Unamortized purchased gas adjustments	8.2	102.6
Other regulatory assets	64.6	72.9
Prepayments	31	28
Other	22.3	6.2
Total Current Assets	659.6	725.5
Deferred Charges and Other Assets:
Regulatory assets	669.8	791.1
Other	128.9	77.1
Total Deferred Charges and Other Assets	798.7	868.2
Total Assets	6,843.6	6,546.7
Capitalization:
Shareholders’ equity	2,255.4	1,991.3
Redeemable noncontrolling interest	7.9	0
Long-term debt	1,900.1	1,995
Total Capitalization	4,163.4	3,986.3
Current Liabilities:
Current portion of long-term debt	175.5	100
Notes payable	553.6	477.3
Accounts payable	290.1	257.1
Advance customer billings	22.7	32
Wages and compensation accrued	39.7	38.7
Dividends payable	30	26.6
Customer deposits	35.5	34.9
Interest accrued	15.2	14.6
Taxes accrued	65.4	61
Unamortized purchased gas adjustments	2.9	1
Other regulatory liabilities	32.8	21.6
Other	58.3	33.1
Total Current Liabilities	1,321.7	1,097.9
Deferred Credits and Other Liabilities:
Deferred income taxes	435.8	707.5
Pension and postretirement benefit costs	180.2	237.4
Asset retirement obligations	321.1	296.6
Regulatory liabilities	354.6	157.2
Other	66.8	63.8
Total Deferred Credits and Other Liabilities	1,358.5	1,462.5
Commitments and Contingencies
Total Capitalization and Liabilities	6,843.6	6,546.7
Spire Missouri
ASSETS
Utility Plant	3,331	3,091.8
Less: Accumulated depreciation and amortization	705.8	681.6
Net Utility Plant	2,625.2	2,410.2
Goodwill	210.2	210.2
Other investments	55	59.4
Other Property and Investments	265.2	269.6
Current Assets:
Cash and cash equivalents	2	2.5
Accounts receivable:
Utility	103.9	101.7
Associated companies	2.7	3.3
Other	16.6	15
Allowance for doubtful accounts	(16)	(14.1)
Delayed customer billings	6.9	3.4
Inventories:
Natural gas	127.9	138.2
Propane gas	12	12
Materials and supplies	13.2	11.3
Derivative instrument assets	0	0.1
Unamortized purchased gas adjustments	1	57.4
Other regulatory assets	29.7	38.2
Prepayments	19.1	19.6
Total Current Assets	319	388.6
Deferred Charges and Other Assets:
Regulatory assets	441.1	557.8
Other	50.8	5.3
Total Deferred Charges and Other Assets	491.9	563.1
Total Assets	3,701.3	3,631.5
Capitalization:
Shareholders’ equity	1,259.9	1,171
Long-term debt	824.4	873.9
Total Capitalization	2,084.3	2,044.9
Current Liabilities:
Current portion of long-term debt	50	100
Notes payable – associated companies	345.3	203
Accounts payable	81.7	89.9
Accounts payable – associated companies	5.8	5.4
Advance customer billings	9.5	13.3
Wages and compensation accrued	31.3	29.6
Dividends payable	9	0
Customer deposits	13.1	13.3
Interest accrued	7.8	8
Taxes accrued	32	34.1
Unamortized purchased gas adjustments	1.9	0
Other regulatory liabilities	14.8	2.7
Other	20.1	8.5
Total Current Liabilities	622.3	507.8
Deferred Credits and Other Liabilities:
Deferred income taxes	361	623.8
Pension and postretirement benefit costs	136.9	173
Asset retirement obligations	174.1	158.6
Regulatory liabilities	274.9	81.2
Other	47.8	42.2
Total Deferred Credits and Other Liabilities	994.7	1,078.8
Commitments and Contingencies
Total Capitalization and Liabilities	3,701.3	3,631.5
Spire Alabama
ASSETS
Utility Plant	1,964.3	1,838
Less: Accumulated depreciation and amortization	830.2	782
Net Utility Plant	1,134.1	1,056
Current Assets:
Cash and cash equivalents	0	0.1
Accounts receivable:
Utility	39.6	32
Associated companies	0.5	0
Other	8.5	6.2
Allowance for doubtful accounts	(3.9)	(2.6)
Inventories:
Natural gas	33.9	33.9
Materials and supplies	7.8	6.5
Unamortized purchased gas adjustments	6.4	45.2
Other regulatory assets	19.8	19.4
Prepayments	6	4.9
Other	2.4	1.8
Total Current Assets	121	147.4
Deferred Charges and Other Assets:
Regulatory assets	201.5	197
Deferred income tax	101.8	185.6
Other	57.8	57
Total Deferred Charges and Other Assets	361.1	439.6
Total Assets	1,616.2	1,643
Capitalization:
Shareholders’ equity	808.7	867.4
Long-term debt	322.6	247.8
Total Capitalization	1,131.3	1,115.2
Current Liabilities:
Notes payable – associated companies	142.5	169.9
Accounts payable	48.4	44.4
Accounts payable – associated companies	2.1	1.6
Advance customer billings	13.1	18.6
Wages and compensation accrued	6.7	7.4
Customer deposits	18.6	17.9
Interest accrued	3.9	3.3
Taxes accrued	28.3	23.4
Other regulatory liabilities	7.6	12
Other	3.2	2.9
Total Current Liabilities	274.4	301.4
Deferred Credits and Other Liabilities:
Pension and postretirement benefit costs	35	50.2
Asset retirement obligations	135.7	128.4
Regulatory liabilities	31.3	39.6
Other	8.5	8.2
Total Deferred Credits and Other Liabilities	210.5	226.4
Total Capitalization and Liabilities	$ 1,616.2	$ 1,643

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Assets
Non-utility property, accumulated depreciation and amortization	$ 10.4	$ 8.6

CONSOLIDATED STATEMENTS OF CAPI

CONSOLIDATED STATEMENTS OF CAPITALIZATION - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Common Stock Equity:
Common stock, par value $1 per share	$ 50.7	$ 48.3
Paid-in capital	1,482.7	1,325.6
Retained earnings	715.6	614.2
Accumulated other comprehensive income	6.4	3.2
Total Shareholders’ Equity	2,255.4	1,991.3
Redeemable noncontrolling interest	7.9	0
Long-Term Debt
Total Principal of Long-Term Debt	1,916.5	2,012
Unamortized debt issuance costs	(14)	(15.2)
Unamortized discounts on long-term debt	(2.4)	(1.8)
Total Long-term Debt	1,900.1	1,995
Total Capitalization	4,163.4	3,986.3
3.92% Notes, due January 15, 2048
Long-Term Debt
Total Principal of Long-Term Debt	45	0
4.02% Notes, due January 15, 2058
Long-Term Debt
Total Principal of Long-Term Debt	30	0
Spire | 2.55% Senior Notes, due August 15, 2019
Long-Term Debt
Total Principal of Long-Term Debt	0	125
Spire | 2.52% Senior Notes, due September 1, 2021
Long-Term Debt
Total Principal of Long-Term Debt	35	35
Spire | 3.31% Notes Payable, due December 15, 2022
Long-Term Debt
Total Principal of Long-Term Debt	25	25
Spire | 3.54% Senior Notes, due February 27, 2024
Long-Term Debt
Total Principal of Long-Term Debt	150	150
Spire | 3.13% Senior Notes, due September 1, 2026
Long-Term Debt
Total Principal of Long-Term Debt	130	130
Spire | 3.93% Senior Notes, due March 15, 2027
Long-Term Debt
Total Principal of Long-Term Debt	100	100
Spire | 4.70% Senior Notes, due August 15, 2044
Long-Term Debt
Total Principal of Long-Term Debt	250	250
Spire Missouri
Common Stock Equity:
Common stock, par value $1 per share	0.1	0.1
Paid-in capital	760.3	756.1
Retained earnings	501.1	416.5
Accumulated other comprehensive income	(1.6)	(1.7)
Total Shareholders’ Equity	1,259.9	1,171
Long-Term Debt
Total Principal of Long-Term Debt	830	880
Unamortized debt issuance costs	(4.3)	(4.6)
Unamortized discounts on long-term debt	(1.3)	(1.5)
Total Long-term Debt	824.4	873.9
Total Capitalization	2,084.3	2,044.9
Spire Missouri | 5.5% Series, due May 1, 2019
Long-Term Debt
Total Principal of Long-Term Debt	0	50
Spire Missouri | 3.0% Series, due March 15, 2023
Long-Term Debt
Total Principal of Long-Term Debt	55	55
Spire Missouri | 3.4% Series, due August 15, 2023
Long-Term Debt
Total Principal of Long-Term Debt	250	250
Spire Missouri | 3.4% Series, due March 15, 2028
Long-Term Debt
Total Principal of Long-Term Debt	45	45
Spire Missouri | 7.0% Series, due June 1, 2029
Long-Term Debt
Total Principal of Long-Term Debt	25	25
Spire Missouri | 7.9% Series, due September 15, 2030
Long-Term Debt
Total Principal of Long-Term Debt	30	30
Spire Missouri | 3.68% Series, due September 15, 2032
Long-Term Debt
Total Principal of Long-Term Debt	50	50
Spire Missouri | 6.0% Series, due May 1, 2034
Long-Term Debt
Total Principal of Long-Term Debt	100	100
Spire Missouri | 6.15% Series, due June 1, 2036
Long-Term Debt
Total Principal of Long-Term Debt	55	55
Spire Missouri | 4.625% Series, due August 15, 2043
Long-Term Debt
Total Principal of Long-Term Debt	100	100
Spire Missouri | 4.23% Series, due September 15, 2047
Long-Term Debt
Total Principal of Long-Term Debt	70	70
Spire Missouri | 4.38% Series, due September 15, 2057
Long-Term Debt
Total Principal of Long-Term Debt	50	50
Spire Alabama
Common Stock Equity:
Common stock, par value $1 per share, and paid-in capital	390.9	420.9
Retained earnings	417.8	446.5
Total Shareholders’ Equity	808.7	867.4
Long-Term Debt
Total Principal of Long-Term Debt	325	250
Unamortized debt issuance costs	(2.4)	(2.2)
Total Long-term Debt	322.6	247.8
Total Capitalization	1,131.3	1,115.2
Spire Alabama | 5.2% Notes, due January 15, 2020
Long-Term Debt
Total Principal of Long-Term Debt	40	40
Spire Alabama | 3.86% Notes, due December 22, 2021
Long-Term Debt
Total Principal of Long-Term Debt	50	50
Spire Alabama | 3.21% Notes, due September 15, 2025
Long-Term Debt
Total Principal of Long-Term Debt	35	35
Spire Alabama | 5.9% Notes, due January 15, 2037
Long-Term Debt
Total Principal of Long-Term Debt	45	45
Spire Alabama | 4.31% Notes, due December 1, 2045
Long-Term Debt
Total Principal of Long-Term Debt	80	80
Spire Alabama | 3.92% Notes, due January 15, 2048
Long-Term Debt
Total Principal of Long-Term Debt	45	0
Spire Alabama | 4.02% Notes, due January 15, 2058
Long-Term Debt
Total Principal of Long-Term Debt	30	0
Other | 3.10% Note, due December 30, 2018
Long-Term Debt
Total Principal of Long-Term Debt	0	5
Other | 4.14% First Mortgage Bonds, due September 30, 2021
Long-Term Debt
Total Principal of Long-Term Debt	20	20
Other | 5.00% First Mortgage Bonds, due September 30, 2031
Long-Term Debt
Total Principal of Long-Term Debt	42	42
Other | Non-interest-bearing Note, due December 27, 2022
Long-Term Debt
Total Principal of Long-Term Debt	$ 9.5	$ 0

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares	Sep. 30, 2018	Sep. 30, 2017
Long - Term Debt
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)	50,671,903	48,263,243
Spire Missouri
Long - Term Debt
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 | 5.5% Series, due May 1, 2019
Long - Term Debt
Debt instrument, interest rate, stated percentage	5.50%	5.50%
Spire Missouri | 3.0% Series, due March 15, 2023
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.00%	3.00%
Spire Missouri | 3.4% Series, due August 15, 2023
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.40%	3.40%
Spire Missouri | 3.4% Series, due March 15, 2028
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.40%	3.40%
Spire Missouri | 7.0% Series, due June 1, 2029
Long - Term Debt
Debt instrument, interest rate, stated percentage	7.00%	7.00%
Spire Missouri | 7.9% Series, due September 15, 2030
Long - Term Debt
Debt instrument, interest rate, stated percentage	7.90%	7.90%
Spire Missouri | 6.0% Series, due May 1, 2034
Long - Term Debt
Debt instrument, interest rate, stated percentage	6.00%	6.00%
Spire Missouri | 6.15% Series, due June 1, 2036
Long - Term Debt
Debt instrument, interest rate, stated percentage	6.15%	6.15%
Spire Missouri | 4.625% Series, due August 15, 2043
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.625%	4.625%
Spire Missouri | 3.68% Series, due September 15, 2032
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.68%	3.68%
Spire Missouri | 4.23% Series, due September 15, 2047
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.23%	4.23%
Spire Missouri | 4.38% Series, due September 15, 2057
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.38%	4.38%
Spire Alabama
Long - Term Debt
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
Debt instrument, interest rate, stated percentage	5.20%	5.20%
Spire Alabama | 3.86% Notes, due December 22, 2021
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.86%	3.86%
Spire Alabama | 3.21% Notes, due September 15, 2025
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.21%	3.21%
Spire Alabama | 5.9% Notes, due January 15, 2037
Long - Term Debt
Debt instrument, interest rate, stated percentage	5.90%	5.90%
Spire Alabama | 4.31% Notes, due December 1, 2045
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.31%	4.31%
Spire Alabama | 3.92% Notes, due January 15, 2048
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.92%	3.92%
Spire Alabama | 4.02% Notes, due January 15, 2058
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.02%	4.02%
Other | 3.10% Note, due December 30, 2018
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.10%	3.10%
Other | 4.14% First Mortgage Bonds, due September 30, 2021
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.14%	4.14%
Other | 5.00% First Mortgage Bonds, due September 30, 2031
Long - Term Debt
Debt instrument, interest rate, stated percentage	5.00%	5.00%
Spire | 2.55% Senior Notes, due August 15, 2019
Long - Term Debt
Debt instrument, interest rate, stated percentage	2.55%	2.55%
Spire | 2.52% Senior Notes, due September 1, 2021
Long - Term Debt
Debt instrument, interest rate, stated percentage	2.52%	2.52%
Spire | 3.31% Notes Payable, due December 15, 2022
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.31%	3.31%
Spire | 3.54% Senior Notes, due February 27, 2024
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.54%	3.54%
Spire | 3.13% Senior Notes, due September 1, 2026
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.13%	3.13%
Spire | 3.93% Senior Notes, due March 15, 2027
Long - Term Debt
Debt instrument, interest rate, stated percentage	3.93%	3.93%
Spire | 4.70% Senior Notes, due August 15, 2044
Long - Term Debt
Debt instrument, interest rate, stated percentage	4.70%	4.70%

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF 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, 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										0
Common stock offering	133.2	$ 2.2	131								(29)		(29)
Dividend reinvestment plan (in shares)		22,878
Dividend reinvestment plan	1.4	$ 0	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)		(31.5)			(31.5)
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	8.3		7.4	0.9		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
Net income	214.2			214.2		129.3			129.3		1.3			1.3
Common stock offering (in shares)		2,300,000
Common stock offering	153	$ 2.3	150.7
Dividend reinvestment plan (in shares)		23,023
Dividend reinvestment plan	1.6		1.6
Stock-based compensation costs						4.2		4.2
Stock issued under stock-based compensation plans (in shares)		119,592
Stock issued under stock-based compensation plans	0	$ 0.1	(0.1)	0
Employees’ tax withholding for stock-based compensation (in shares)		(33,955)
Employees’ tax withholding for stock-based compensation	(2.8)		(2.8)
Dividends declared	(112.1)			(112.1)		(45)			(45)		(30)			(30)
Return of capital to Spire											(30)		(30)
Other comprehensive loss, net of tax	2.5				2.5	0.4				0.4
Reclassification of certain income tax effects	0.7			(0.7)	0.7	(0.3)			0.3	(0.3)
BALANCE (in shares) at Sep. 30, 2018		50,671,903					24,577					1,972,052
BALANCE at Sep. 30, 2018	2,255.4	$ 50.7	1,482.7	715.6	$ 6.4	$ 1,259.9	$ 0.1	$ 760.3	$ 501.1	$ (1.6)	$ 808.7	$ 0	$ 390.9	$ 417.8
Stockholders' Equity Rollforward
Stock-based compensation costs (After Adoption)	$ 7.7		$ 7.7	$ 0

CONSOLIDATED STATEMENTS OF SH_2

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement of Stockholders' Equity [Abstract]
Dividends declared, common stock (in dollars per share)	$ 2.25	$ 2.10	$ 1.96

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Operating Activities:
Net income	$ 214.2	$ 161.6	$ 144.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	168.4	154.1	137.5
Deferred income taxes and investment tax credits	(28.7)	77	68.8
Changes in assets and liabilities:
Accounts receivable	(32.7)	(63)	(12.3)
Inventories	15.5	(23.5)	16.5
Unamortized purchased gas adjustments	109	(50.9)	(52.8)
Accounts payable	12.6	51.1	30
Delayed/advance customer billings, net	(12.8)	(40)	26.9
Taxes accrued	6.4	5.8	(0.4)
Other assets and liabilities	(39.5)	11.9	(35)
Other	44.2	4.2	4.9
Net cash provided by operating activities	456.6	288.3	328.3
Investing Activities:
Capital expenditures	(499.4)	(438.1)	(293.3)
Acquisition of Spire EnergySouth (net of $2.0 cash acquired) and final settlement	0	3.8	(317.7)
Other business acquisitions	(28.1)	0	0
Other	(4.2)	0.8	(1.7)
Net cash used in investing activities	(531.7)	(433.5)	(612.7)
Financing Activities:
Issuance of long-term debt	75	420	245
Repayment of long-term debt	(105)	(393.8)	(80)
Issuance of short-term debt, net	76.3	78.6	60.7
Issuance of common stock	154.7	146.9	137.1
Dividends paid	(108.7)	(96.2)	(85.2)
Other	(3.2)	(8.1)	(1.8)
Net cash provided by financing activities	89.1	147.4	275.8
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	14	2.2	(8.6)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	7.4	5.2	13.8
Cash, Cash Equivalents, and Restricted Cash at End of Year	21.4	7.4	5.2
Cash, Cash Equivalents at Beginning of Period	7.4
Cash, Cash Equivalents at End of Period	4.4	7.4
Supplemental disclosure of cash (paid) refunded for:
Interest, net of amounts capitalized	(95.1)	(85.5)	(72.5)
Income taxes	(1.5)	(1.3)	2.9
Spire Missouri
Operating Activities:
Net income	129.3	113	105.9
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	102.8	93.1	88.6
Deferred income taxes and investment tax credits	(32.6)	47.5	45.3
Changes in assets and liabilities:
Accounts receivable	(2)	(20.5)	35.7
Inventories	8.4	(13)	11
Unamortized purchased gas adjustments	71	(11.6)	(18.7)
Accounts payable	(14.8)	16.8	0.9
Delayed/advance customer billings, net	(7.4)	(37.6)	24.9
Taxes accrued	(2.1)	5	4.9
Other assets and liabilities	(13.4)	(11.6)	(29.6)
Other	45	1.6	2.3
Net cash provided by operating activities	284.2	182.7	271.2
Investing Activities:
Capital expenditures	(295.8)	(282.2)	(197.8)
Other	4.8	1.1	1.1
Net cash used in investing activities	(291)	(281.1)	(196.7)
Financing Activities:
Issuance of first mortgage bonds	0	170	0
Issuance of short-term debt, net	(100)	(243.7)	10.7
Borrowings from Spire	142.3	203	0
Dividends paid	(36)	(28.7)	(84.8)
Other	0	(1.8)	0
Net cash provided by financing activities	6.3	98.8	(74.1)
Net (Decrease) Increase in Cash and Cash Equivalents	(0.5)	0.4	0.4
Cash, Cash Equivalents at Beginning of Period	2.5	2.1	1.7
Cash, Cash Equivalents at End of Period	2	2.5	2.1
Supplemental disclosure of cash (paid) refunded for:
Interest, net of amounts capitalized	(45.6)	(38.6)	(35.7)
Income taxes	0	0	2.1
Spire Alabama
Operating Activities:
Net income	1.3	58.1	53.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	53.2	49.9	47.8
Deferred income taxes and investment tax credits	81.6	35.8	33.2
Changes in assets and liabilities:
Accounts receivable	(16.2)	(10)	(11.1)
Inventories	(1.2)	0.1	5.3
Unamortized purchased gas adjustments	38.8	(39.6)	(33.8)
Accounts payable	4.7	8.8	9.1
Delayed/advance customer billings, net	(5.5)	(2.5)	2
Taxes accrued	4.9	1.8	(5.2)
Other assets and liabilities	(15.1)	(16.6)	(3.2)
Other	(0.4)	(1.3)	0.9
Net cash provided by operating activities	146.1	84.5	98.2
Investing Activities:
Capital expenditures	(131.7)	(113.9)	(93.4)
Other	(1.6)	(0.4)	(2.5)
Net cash used in investing activities	(133.3)	(114.3)	(95.9)
Financing Activities:
Issuance of long-term debt	75	0	80
Repayment of long-term debt	0	0	(80)
Issuance of short-term debt, net	0	(82)	51
(Repayments of) borrowings from Spire	(27.4)	169.9	0
Return of capital to Spire	(30)	(31)	(29)
Dividends paid	(30)	(27)	(31.5)
Other	(0.5)	0	0
Net cash provided by financing activities	(12.9)	29.9	(9.5)
Net (Decrease) Increase in Cash and Cash Equivalents	(0.1)	0.1	(7.2)
Cash, Cash Equivalents at Beginning of Period	0.1	0	7.2
Cash, Cash Equivalents at End of Period	0	0.1	0
Supplemental disclosure of cash (paid) refunded for:
Interest, net of amounts capitalized	(15.1)	(12.8)	(12.4)
Income taxes	$ 0	$ 0	$ 0.8

CONSOLIDATED STATEMENTS OF CA_3

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Statement of Cash Flows [Abstract]
Cash acquired from acquisition	$ 2

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Sep. 30, 2018
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, Spire Alabama and the subsidiaries of Spire EnergySouth Inc. (“Spire EnergySouth”) are collectively referred to as “the Utilities.” The subsidiaries of Spire EnergySouth are Spire Gulf Inc. and Spire Mississippi Inc. 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 include the accounts of the Company and all its subsidiaries. One subsidiary acquired an 80% voting interest in a natural gas storage facility in December 2017, and the redeemable noncontrolling interest is shown as temporary equity on the balance sheet. Transactions and balances between consolidated entities have been eliminated from the consolidated financial statements of Spire. 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. NATURE OF OPERATIONS – Spire (NYSE: SR) 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”); Spire Alabama, serving central and northern Alabama; and the subsidiaries of Spire EnergySouth, serving southern Alabama and south-central Mississippi. The Gas Marketing Segment includes Spire’s primary non-utility business, Spire Marketing Inc. (“Spire Marketing”), which provides non-regulated natural gas services. The activities of other subsidiaries are reported as Other and are described in Note 13 , Information by Operating Segment. 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 2018 , 2017 and 2016 , 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 in fiscal years 2018 , 2017 and 2016 was 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 until paid. September 30 2018 2017 2016 Spire $ 62.1 $ 41.0 $ 30.4 Spire Missouri 36.7 28.9 14.8 Spire Alabama 8.9 9.4 6.8 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 2018 2017 2018 2017 2018 2017 Asset retirement obligations, beginning of year $ 296.6 $ 206.4 $ 158.6 $ 75.2 $ 128.4 $ 120.1 Liabilities incurred during the period 5.5 5.5 0.6 0.3 3.5 5.2 Liabilities settled during the period (11.2 ) (4.6 ) (8.9 ) (1.1 ) (1.8 ) (1.9 ) Accretion 12.7 9.1 6.6 3.6 5.6 5.0 Revisions in estimated cash flows 16.9 80.2 17.2 80.6 — — Business combinations 0.6 — — — — — Asset retirement obligations, end of year $ 321.1 $ 296.6 $ 174.1 $ 158.6 $ 135.7 $ 128.4 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 14 , Regulatory Matters. 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, 2018 and September 30, 2017 was less than the LIFO cost by $14.5 and $20.8 , respectively. The carrying value of the Utilities’ inventory is not adjusted to the lower of net realizable value or market prices because, pursuant to Purchased Gas Adjustment (“PGA”) clauses or a Gas Supply Adjustment (“GSA”) rider, 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 – Spire’s acquisitions, including the recent transactions described below, were accounted for 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. Effective September 12, 2016, Spire completed the acquisition of 100% of the common stock of Spire EnergySouth. Total cash consideration paid, net of cash acquired, debt assumed and a working capital settlement payment received, was $313.9 . 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. 2018 2017 2016 Total Operating Revenues $ 102.1 $ 95.5 $ 3.3 Net Income (Loss) 13.8 9.4 (0.2 ) 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 2016. 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. 2018 2017 2016 Total Operating Revenues $ 1,965.0 $ 1,740.7 $ 1,632.4 Net Income 214.2 161.6 153.9 Basic Earnings Per Share $ 4.35 $ 3.44 $ 3.48 Diluted Earnings Per Share 4.33 3.43 3.46 In December 2017, the Company acquired an 80% voting interest in a natural gas storage facility in Wyoming. The transaction was valued at $24.8 , consisting of $16.0 in cash and a $10.0 non-interest-bearing note valued at $8.8 . In October 2018, the Company completed the exercise of its right to call the remaining 20% voting interest in that facility and settled the related note for a combined total of $17.0 . In May 2018, the Company expanded its operations by acquiring 100% of a neighboring natural gas storage facility for $12.2 in cash. Together, these storage operations are referred to herein as “Spire Storage.” 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, 2018, 2017 and 2016, 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, 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 Balance as of September 30, 2018 $ 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, 2018 and 2017 were $29.7 and $30.1 , 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 amount of accrued unbilled revenues for Spire Alabama was $1.9 at both September 30, 2018 and 2017 . 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 their business, certain subsidiaries of the Company enter 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 9 , 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 realized or settled. The effects on deferred tax assets and liabilities of a change in enacted tax rates is recognized in income or loss for non-regulated operations, and in a regulatory asset or regulatory liability for regulated operations. 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. For additional information on the accounting for income taxes, refer to Note 11 , Income Taxes. CASH, CASH EQUIVALENTS, AND RESTRICTED CASH – 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. In Spire’s statements of cash flows, total cash, cash equivalents, and restricted cash included $17.0 of restricted cash reported in “Other” current assets on Spire’s balance sheet as of September 30, 2018 (in addition to amounts shown as “Cash and cash equivalents”). This restricted cash was an escrow deposit for the purchase of the remaining 20% interest in a natural gas storage business and the settlement of the related note payable, and the transaction was completed on October 25, 2018. 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 3 , 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: 2018 2017 2016 Spire $ 98.2 $ 84.6 $ 75.5 Spire Missouri 68.9 60.7 57.4 Spire Alabama 25.4 19.5 17.9 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 they participated in normal intercompany shared services transactions. In addition, Spire Missouri’s other transactions with affiliates included: 2018 2017 2016 Purchases of natural gas from Spire Marketing $ 71.5 $ 74.4 $ 46.3 Sales of natural gas to Spire Marketing 0.3 7.8 1.9 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 Spire Missouri Spire Alabama 2018 2017 2016 2018 2017 2016 2018 2017 2016 Allowance at beginning of year $ 18.3 $ 20.5 $ 14.2 $ 14.1 $ 16.1 $ 10.0 $ 2.6 $ 3.3 $ 4.2 Additions charged to expense 14.6 10.6 6.5 11.9 10.1 6.2 2.1 0.2 0.6 Net deductions (10.5 ) (12.8 ) (0.2 ) (10.0 ) (12.1 ) (0.1 ) (0.8 ) (0.9 ) (1.5 ) Allowance at end of year $ 22.4 $ 18.3 $ 20.5 $ 16.0 $ 14.1 $ 16.1 $ 3.9 $ 2.6 $ 3.3 FINANCE RECEIVABLES – Spire Alabama finances third party contractor sales of merchandise including gas furnaces and appliances. At September 30, 2018 and September 30, 2017 , the Company’s finance receivable totaled approximately $13.1 and $12.5 , 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. 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, 2018 and September 30, 2017 . 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 7 , Fair Value of Financial Instruments, Note 8 , Fair Value Measurements, and Note 12 , Pension Plans and Other Postretirement Benefits. STOCK-BASED COMPENSATION – The Company accounts for share-based compensation arrangements in accordance with ASC Topic 718, Compensation - Stock 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, forfeitures are recognized in the period they occur. Prior to fiscal 2017, forfeitures were estimated at the time of grant and revised, when necessary, in subsequent periods when the actual forfeitures differed from those estimates. Refer to Note 2 , Stock-Based Compensation, for further discussion of the accounting for the Company’s stock-based compensation plans. NEW ACCOUNTING PRONOUNCEMENTS – In November 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-18, Statement of Cash Flows: Restricted Cash . This guidance requires the statement of cash flows to present changes in the total of cash, cash equivalents and restricted cash. Prior to the adoption of this ASU, the relevant accounting guidance did not require the statement of cash flows to include changes in restricted cash. The Company, Spire Missouri and Spire Alabama adopted the standard retrospectively in 2018 with no impact to 2017 or 2016. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . This guidance permits companies to make an election to reclassify stranded income tax effects from the recently enacted Tax Cuts and Jobs Act included in accumulated other comprehensive income or loss (“AOCI”) to retained earnings. ASU 2018-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company, Spire Missouri and Spire Alabama elected to early adopt this guidance in the quarter ended September 30, 2018. The reclassifications from the adoption of this standard are shown on the statements of shareholders’ equity of the Company and Spire Missouri. There was no effect for Spire Alabama. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers . Under the new standard, an entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under previous guidance. ASU No. 2014-09 also requires disclosures that will enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Existing alternative revenue program guidance, though excluded by the FASB in updating specific guidance associated with revenue from contracts with customers, was relocated without substantial modification to accounting guidance for rate-regulated entities. It will require separate presentation of such revenues in the statement of income. Entities have the option of using either a full retrospective or modified retrospective approach in adopting this guidance. In August 2015, the FASB issued ASU No. 2015-14, which made the guidance in ASU No. 2014-09 effective for fiscal years beginning after December 15, 2017, and interim periods within those years. In 2016 and 2017, the FASB issued related ASU Nos. 2016-08, 2016-10, 2016-11, 2016-12, 2016-20, and 2017-14, which further modified the standards for accounting for revenue. The Company, Spire Missouri and Spire Alabama have completed their evaluation of their sources of revenue and related contracts and plan to adopt the new guidance in the first quarter of fiscal 2019 using the modified retrospective approach with no material effect on their financial position, results of operations, or cash flows. In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard requires lessees to recognize a right-of-use asset and lease li

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The Spire 2015 Equity Incentive Plan (“EIP”) was approved by shareholders of Spire on January 29, 2015 and amended on November 9, 2017. The purpose of the EIP is to encourage directors, officers, and key 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 EIP that may be earned by achieving performance objectives and/or other criteria as determined by the Committee. Under the terms of the EIP, officers and employees of the Company and its subsidiaries, as determined by the Committee, are eligible to be selected for awards. The EIP 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 EIP 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 EIP is 1,000,000 . The Company issues new shares to satisfy employee restricted stock awards and stock option exercises. Restricted Stock Awards During fiscal 2018 , the Company granted 87,960 performance-contingent restricted share units to executive officers and key employees at a weighted average grant date fair value of $79.88 per share. This number represents the target shares that can be earned pursuant to the terms of the awards. The share units have a performance period ending September 30, 2021. 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 maximum amount of shares that can be earned pursuant to the terms of the awards is 200% of the target units granted. The weighted average grant date fair value of performance-contingent restricted share units granted during fiscal years 2017 and 2016 was $58.45 and $62.38 per share, respectively. Fiscal 2018 activity of restricted stock units subject to performance and/or market conditions is presented below: Units Weighted Average Grant Date Fair Value Per Unit Nonvested at September 30, 2017 282,015 $ 56.32 Granted 87,960 $ 79.88 Vested (81,933 ) $ 47.80 Forfeited (21,960 ) $ 56.73 Nonvested at September 30, 2018 266,082 $ 66.69 For the year ended September 30, 2018, the total number of shares that could be issued if all outstanding award grants attain maximum performance payout is 532,164 . During fiscal 2018 , the Company granted 37,980 shares of time-vested restricted stock to executive officers and key employees at a weighted average grant date fair value of $76.60 per share. Unless forfeited based on terms of the agreements, these shares will vest in fiscal 2021. 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 2017 and 2016 was $63.05 and $59.40 per share, respectively. During fiscal 2018 , the Company granted 9,800 shares of time-vested restricted stock to non-employee directors at a weighted average grant date fair value of $63.20 per share. These shares vested in fiscal 2018, six months after the grant date. The weighted average grant date fair value of restricted stock awarded to non-employee directors during fiscal years 2017 and 2016 was $63.45 and $63.93 per share, respectively. Time-vested restricted stock and stock unit activity for fiscal 2018 is presented below: Shares/ Units Weighted Average Grant Date Fair Value Per Share Nonvested at September 30, 2017 110,940 $ 55.85 Granted 47,780 $ 73.85 Vested (47,928 ) $ 53.48 Forfeited (7,192 ) $ 65.25 Nonvested at September 30, 2018 103,600 $ 64.60 For restricted stock and stock units (performance-contingent and time-vested) that vested during fiscal years 2018, 2017, and 2016, the Company withheld 34,922 shares, 35,514 shares and 30,712 shares, respectively, at weighted average prices of $81.65 , $63.83 and $57.29 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 2018 , 2017 , and 2016 was $10.5 , $8.9 , and $6.3 , respectively, and the related tax benefit was $4.0 , $3.3 , and $2.4 , respectively. None of the tax benefits have been realized. Stock Option Awards No stock options were granted during fiscal years 2018 , 2017 and 2016 . There was no stock option activity in fiscal 2018 or 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 . 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 (“U.S.”) 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 2018 , 2017 and 2016 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: 2018 2017 2016 Risk-free interest rate 1.76% 1.39% 1.14% Expected dividend yield of stock — — — Expected volatility of stock 16.0% 16.3% 15.0% Vesting period 2.9 years 2.8 years 2.8 years The risk-free interest rate was based on the yield on U.S. 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: 2018 2017 2016 Total compensation cost $ 6.9 $ 7.4 $ 6.7 Compensation cost capitalized (1.3 ) (3.3 ) (2.2 ) Prior period disallowed stock compensation capitalization $ 6.9 $ — $ — Compensation cost recognized in net income 12.5 4.1 4.5 Income tax benefit recognized in net income (4.0 ) (1.5 ) (1.7 ) Compensation cost recognized in net income, net of income tax $ 8.5 $ 2.6 $ 2.8 As of September 30, 2018 , there was $9.4 of total unrecognized compensation cost related to non-vested share-based compensation arrangements, which 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
	Sep. 30, 2018
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	EARNINGS PER COMMON SHARE 2018 2017 2016 Basic Earnings Per Share: Net Income $ 214.2 $ 161.6 $ 144.2 Less: Income allocated to participating securities 0.5 0.4 0.5 Net Income Available to Common Shareholders $ 213.7 $ 161.2 $ 143.7 Weighted Average Shares Outstanding (in millions) 49.1 46.9 44.1 Basic Earnings Per Share of Common Stock $ 4.35 $ 3.44 $ 3.26 Diluted Earnings per Share: Net Income $ 214.2 $ 161.6 $ 144.2 Less: Income allocated to participating securities 0.5 0.4 0.5 Net Income Available to Common Shareholders $ 213.7 $ 161.2 $ 143.7 Weighted Average Shares Outstanding (in millions) 49.1 46.9 44.1 Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* 0.2 0.1 0.2 Weighted Average Diluted Shares (in millions) 49.3 47.0 44.3 Diluted Earnings Per Share of Common Stock $ 4.33 $ 3.43 $ 3.24 * Calculation excludes certain outstanding shares (shown in millions by period at the right) attributable to stock units subject to performance or market conditions and restricted stock, which could have a dilutive effect in the future 0.4 0.5 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.

SHAREHOLDERS' EQUITY

SHAREHOLDERS' EQUITY	12 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
SHAREHOLDERS' EQUITY	SHAREHOLDERS’ EQUITY Spire 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 April 3, 2017, Spire settled purchase contracts underlying equity units issued in 2014 by issuing 2,504,684 shares of its common stock, generating net cash proceeds of approximately $142.0 . Spire has a shelf registration statement on Form S-3 on file with the U.S. Securities and Exchange Commission (“SEC”) for the issuance of equity and debt securities, which expires September 23, 2019. Under that registration statement, on May 10, 2018, Spire issued and sold 2,300,000 shares of its common stock at a public offering price of $68.75 per share. Spire filed a registration statement on Form S-3 with the 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 221,107 and 216,678 shares at September 30, 2018 and November 12, 2018 , respectively, remaining available for issuance under this Form S-3. At September 30, 2018 and 2017 , 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, 2018 and 2017 , the amount under the mortgage’s formula that was available to pay dividends was $1,097.6 and $1,010.8 , respectively. Thus, all of Spire Missouri’s retained earnings were free from such dividend restrictions as of those dates. Spire Missouri is authorized by the MoPSC to issue registered securities (first mortgage bonds, unsecured debt and preferred stock), issue common stock, and issue private placement debt in an aggregate amount of up to $500.0 for financings placed any time before September 30, 2021. At September 30, 2018 and 2017 , Spire Missouri had authorized 1,480,000 shares of preferred stock, but none were issued and outstanding. Spire Alabama At September 30, 2018 and 2017 , Spire Alabama had authorized 120,000 shares of preferred stock, but none were issued and outstanding. Accumulated Other Comprehensive Income The components of AOCI, 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 Debt Securities Total Spire 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 Other comprehensive income 2.0 0.3 0.2 2.5 Reclassification of certain income tax effects 1.0 (0.3 ) — 0.7 Balance at September 30, 2018 $ 7.9 $ (1.5 ) $ — $ 6.4 Spire Missouri 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 ) Other comprehensive (loss) income (0.1 ) 0.3 0.2 0.4 Reclassification of certain income tax effects — (0.3 ) — (0.3 ) Balance at September 30, 2018 $ — $ (1.6 ) $ — $ (1.6 ) 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 AOCI balances.

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT The composition of long-term debt for Spire, Spire Missouri and Spire Alabama is shown in each registrant’s statements of capitalization. Maturities of long-term debt for Spire on a consolidated basis, Spire Missouri and Spire Alabama for the five fiscal years after September 30, 2018 are as follows: 2019 2020 2021 2022 2023 Spire $ 175.5 $ 43.2 $ 57.0 $ 52.0 $ 332.3 Spire Missouri 50.0 — — — 305.0 Spire Alabama — 40.0 — 50.0 — Spire’s, Spire Missouri’s and Spire Alabama’s long-term debt agreements contain customary covenants and default provisions. As of September 30, 2018 , there were no events of default under these covenants. Spire At September 30, 2018 , including the current portion but excluding unamortized discounts and debt issuance costs, Spire had long-term debt totaling $2,092.0 , of which $880.0 was issued by Spire Missouri, $325.0 was issued by Spire Alabama and $72.0 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. Interest expense shown on Spire’s consolidated statement of income is net of capitalized interest totaling $2.6 , $0.8 and $0.2 for the years ended September 30, 2018, 2017 and 2016, respectively. As indicated in Note 4 , 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. Spire Missouri At September 30, 2018 , including the current portion but excluding unamortized discounts and debt issuance costs, Spire Missouri had long-term debt totaling $880.0 . While these long-term debt issues are fixed-rate, they are subject to changes in fair value as market interest rates change. Interest expense shown on Spire Missouri’s statement of income is net of capitalized interest totaling $0.9 , $0.5 and $0.2 for the years ended September 30, 2018, 2017 and 2016, respectively. Spire Missouri is authorized by the MoPSC to issue registered securities (first mortgage bonds, unsecured debt and preferred stock), issue common stock and issue private placement debt in an aggregate amount of up to $500.0 for financings placed any time before September 30, 2021. As indicated in Note 4 , 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 4 , Shareholders’ Equity. Spire Alabama At September 30, 2018 , excluding unamortized debt issuance costs, Spire Alabama had fixed-rate long-term debt totaling $325.0 . While these long-term debt issues are fixed-rate, they are subject to changes in fair value as market interest rates change. Because Spire Alabama has no standing authority to issue long-term debt, it must petition the APSC for each planned issuance.

NOTES PAYABLE AND CREDIT AGREEM

NOTES PAYABLE AND CREDIT AGREEMENTS	12 Months Ended
	Sep. 30, 2018
Short-term Debt [Abstract]
NOTES PAYABLE AND CREDIT AGREEMENTS	NOTES PAYABLE AND CREDIT AGREEMENTS Spire, Spire Missouri and Spire Alabama have a syndicated revolving credit facility pursuant to a loan agreement with 11 banks, expiring October 31, 2023. 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, with commitment fees applied for each borrower relative to its credit rating. Spire may use its line to provide for the funding needs of various subsidiaries. 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, 2018, total debt was 54% of total capitalization for the consolidated Company, 49% for Spire Missouri and 37% for Spire Alabama. Spire has a commercial paper program (“Program”) pursuant to which it 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. Information about Spire’s consolidated short-term borrowings is presented in the following table. Commercial Paper Borrowings Revolving Credit Facility Borrowings Total Short ‑t erm Borrowings Year Ended September 30, 2018 Weighted average borrowings outstanding $408.5 $0.1 $408.6 Weighted average interest rate 2.0% 2.8% 2.0% Range of borrowings outstanding $146.0 - $632.9 $0.0 - $25.0 $146.0 - $632.9 As of September 30, 2018 Borrowings outstanding $553.6 $— $553.6 Weighted average interest rate 2.4% —% 2.4% As of September 30, 2017 Borrowings outstanding $477.3 $— $477.3 Weighted average interest rate 1.5% —% 1.5% From the total short-term borrowings as of September 30, 2018, Spire used $540.5 to provide funding to the Utilities and Spire Storage. Information about Spire Missouri’s and Spire Alabama’s borrowings from Spire is presented in the following table. Spire Missouri Spire Alabama Year Ended September 30, 2018 Weighted average borrowings outstanding $210.5 $103.9 Weighted average interest rate 2.1% 2.0% Range of borrowings outstanding $101.5 - $345.3 $33.6 - $188.6 As of September 30, 2018 Borrowings outstanding $345.3 $142.5 Weighted average interest rate 2.3% 2.3% As of September 30, 2017 Borrowings outstanding $203.0 $169.9 Weighted average interest rate 1.5% 1.5%

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis were as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Spire As of September 30, 2018 Cash and cash equivalents $ 4.4 $ 4.4 $ 4.4 $ — Short-term debt 553.6 553.6 — 553.6 Long-term debt, including current portion 2,075.6 2,074.0 — 2,074.0 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 Spire Missouri As of September 30, 2018 Cash and cash equivalents $ 2.0 $ 2.0 $ 2.0 $ — Short-term debt 345.3 345.3 — 345.3 Long-term debt, including current portion 874.4 906.6 — 906.6 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 Spire Alabama As of September 30, 2018 Short-term debt $ 142.5 $ 142.5 $ — $ 142.5 Long-term debt 322.6 321.7 — 321.7 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

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Sep. 30, 2018
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, 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, 2018 or 2017 . 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 “Other Property and 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 9 , 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, 2018 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 20.3 $ — $ — $ — $ 20.3 NYMEX/ICE natural gas contracts 2.7 — — (2.7 ) — Gas Marketing: NYMEX/ICE natural gas contracts 0.2 4.0 — (4.2 ) — Natural gas commodity contracts — 17.5 — (1.5 ) 16.0 Other: U.S. stock/bond mutual funds 8.9 — — — 8.9 Interest rate swaps — 3.0 — — 3.0 Total $ 32.1 $ 24.5 $ — $ (8.4 ) $ 48.2 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 0.9 10.5 — (11.4 ) — Natural gas commodity contracts — 7.5 0.2 (1.5 ) 6.2 Total $ 2.8 $ 18.0 $ 0.2 $ (14.8 ) $ 6.2 As of September 30, 2017 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — NYMEX 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 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, 2018 ASSETS U.S. stock/bond mutual funds $ 20.3 $ — $ — $ — $ 20.3 NYMEX/ICE natural gas contracts 2.7 — — (2.7 ) — Total $ 23.0 $ — $ — $ (2.7 ) $ 20.3 LIABILITIES NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — As of September 30, 2017 ASSETS U.S. stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — NYMEX 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 ) $ — Spire Alabama Spire Alabama has 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, and there were no gasoline derivatives outstanding as of September 30, 2018.

DERIVATIVE INSTRUMENTS AND HEDG

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	12 Months Ended
	Sep. 30, 2018
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. 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 (including a wholly owned subsidiary), 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, 2018 , the fair values of 277.7 million MMBtu of non-exchange-traded natural gas commodity contracts were reflected in the Consolidated Balance Sheet. Of these contracts, 196.7 million MMBtu will settle during fiscal 2019 , and 43.1 million MMBtu, 30.5 million MMBtu, 7.3 million MMBtu, and 0.1 million MMBtu will settle during fiscal years 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, 2018 , 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 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 $2.5 mark-to-market gain on this swap as part of other comprehensive income for the year ended September 30, 2018. In August 2018, Spire entered into a three -year interest rate swap with a fixed interest rate of 2.7675% and a notional amount of $100.0 to protect itself against adverse movements in interest rates on future variable interest rate payments. The Company recorded a $0.5 mark-to-market gain on this swap as part of other comprehensive income for the year ended September 30, 2018. 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 and ICE natural gas futures and swap positions at September 30, 2018 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 2019 — $ — 7.87 $ 3.04 Fiscal 2020 — — 2.00 2.93 Fiscal 2021 — — 0.14 2.94 NYMEX/ICE open long futures/swap positions Fiscal 2019 24.12 2.80 9.27 2.89 Fiscal 2020 2.68 2.69 2.11 2.85 Fiscal 2021 — — 0.55 2.87 Fiscal 2022 — — 0.25 2.98 Fiscal 2023 — — 0.01 2.86 ICE open short daily swap positions Fiscal 2019 — — 2.54 2.95 ICE open long daily swap positions Fiscal 2019 — — 0.57 2.92 ICE open short basis swap positions Fiscal 2019 — — 52.48 0.23 Fiscal 2020 — — 3.80 0.25 ICE open long basis swap positions Fiscal 2019 — — 49.99 0.64 Fiscal 2020 — — 3.18 0.68 Fiscal 2022 — — 0.92 0.52 Fiscal 2023 — — 0.16 0.52 At September 30, 2018 , Spire Missouri also had 38.4 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, 2018 , 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 Comprehensive Income Location of Gain (Loss) Recorded in Income 2018 2017 2016 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gas Marketing natural gas contracts $ — $ — $ (0.6 ) Gas Utility gasoline and heating oil contracts — 0.1 — Interest rate swaps 3.9 11.4 (3.4 ) Total $ 3.9 $ 11.5 $ (4.0 ) Effective portion of gain (loss) reclassified from AOCI to income: Natural gas contracts Gas Marketing Operating Revenues $ — $ (0.4 ) $ 4.3 Gas Marketing Operating Expenses — 0.1 (4.9 ) Subtotal — (0.3 ) (0.6 ) Gasoline and heating oil contracts Gas Utility Other Operating Expenses 0.1 0.2 (0.5 ) Interest rate swaps Interest Expense 1.4 0.1 — Total $ 1.5 $ — $ (1.1 ) 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 Subtotal — — 0.2 Gasoline and heating oil contracts Gas Utility Other Operating Expenses — — 0.1 Interest rate swaps Interest Expense — 0.5 — Total $ — $ 0.5 $ 0.3 Derivatives Not Designated as Hedging Instruments* Gain (loss) recognized in income on derivatives: Natural gas commodity contracts Gas Marketing Operating Revenues $ 10.2 $ 0.7 $ 12.3 Gas Marketing Operating Expenses (8.1 ) — — NYMEX / ICE natural gas contracts Gas Marketing Operating Revenues — (4.4 ) (1.7 ) Total $ 2.1 $ (3.7 ) $ 10.6 * 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, 2018 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Other: Interest rate swaps Derivative Instrument Assets 3.0 Derivative Instrument Assets — Subtotal 3.0 — Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Accounts Receivable – Other 2.7 Accounts Receivable – Other 1.9 Gas Marketing: NYMEX / ICE natural gas contracts Derivative Instrument Assets 3.8 Derivative Instrument Assets 10.7 Deferred Charges – Other 0.4 Deferred Charges – Other 0.7 Natural gas commodity Derivative Instrument Assets 10.9 Derivative Instrument Assets 1.0 Deferred Charges – Other 6.3 Deferred Charges – Other 0.2 Current Liabilities – Other 0.3 Current Liabilities – Other 6.3 Deferred Credits – Other — Deferred Credits – Other 0.2 Subtotal 24.4 21.0 Total derivatives $ 27.4 $ 21.0 September 30, 2017 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 Derivative Instrument Assets — Derivative Instrument Assets 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 Deferred Charges – Other 0.4 Deferred Charges – Other — 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 * 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 8 , 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: 2018 2017 Fair value of asset derivatives presented above $ 27.4 $ 13.0 Fair value of cash margin (payable) receivable offset with derivatives 6.4 (1.5 ) Netting of assets and liabilities with the same counterparty (14.8 ) (5.3 ) Total $ 19.0 $ 6.2 Derivative Instrument Assets, per Consolidated Balance Sheets: Derivative instrument assets $ 13.3 $ 5.9 Deferred Charges – Other 5.7 0.3 Total $ 19.0 $ 6.2 Fair value of liability derivatives presented above $ 21.0 $ 13.3 Netting of assets and liabilities with the same counterparty (14.8 ) (5.3 ) Total $ 6.2 $ 8.0 Derivative Instrument Liabilities, per Consolidated Balance Sheets: Current Liabilities – Other $ 6.0 $ 4.9 Deferred Credits – Other 0.2 3.1 Total $ 6.2 $ 8.0 Additionally, at September 30, 2018 and 2017 , the Company had $4.1 and $4.0 , 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. These contracts 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. At September 30, 2018 , Spire Missouri had no gasoline futures contracts outstanding. 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, 2018 , it is expected that an immaterial amount of pre-tax gains will be reclassified into the statements of income during fiscal 2019 . 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, 2018 were as follows: MMBtu (millions) Avg. Price Per MMBtu NYMEX/ICE open long futures/swap positions Fiscal 2019 24.12 $ 2.80 Fiscal 2020 2.68 2.69 At September 30, 2018 , Spire Missouri also had 38.4 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 Comprehensive Income Location of Gain (Loss) Recorded in Income 2018 2017 2016 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gasoline and heating oil contracts $ — $ 0.1 $ — Effective portion of gain (loss) reclassified from AOCI to income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ 0.1 $ 0.2 $ (0.5 ) Ineffective portion of gain (loss) on derivatives recognized in income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ — $ — $ 0.1 * 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 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, 2018 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives not designated as hedging instruments Natural gas contracts Accounts Receivable – Other 2.7 Accounts Receivable – Other 1.9 Total derivatives $ 2.7 $ 1.9 September 30, 2017 Derivatives designated as hedging instruments Gasoline and heating oil contracts Derivative Instrument Assets $ 0.1 Derivative Instrument Assets $ — Subtotal 0.1 — 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 * 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 8 , 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: 2018 2017 Fair value of asset derivatives presented above $ 2.7 $ 3.5 Fair value of cash margin (payable) receivable offset with derivatives (0.8 ) (1.5 ) Netting of assets and liabilities with the same counterparty (1.9 ) (1.9 ) Total $ — $ 0.1 Derivative Instrument Assets, per Balance Sheets: Derivative instrument assets $ — $ 0.1 Total $ — $ 0.1 Fair value of liability derivatives presented above $ 1.9 $ 1.9 Netting of assets and liabilities with the same counterparty (1.9 ) (1.9 ) Total $ — $ — Additionally, at September 30, 2017 and 2016, Spire Missouri had $3.8 and $4.0 , respectively, in cash margin receivables not offset with derivatives, which are presented in Accounts Receivable – Other. Spire Alabama 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. Most of these contracts 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. There were no contracts outstanding as of September 30, 2018, and the fair value of gasoline contracts as of September 30, 2017 was not significant.

CONCENTRATIONS OF CREDIT RISK

CONCENTRATIONS OF CREDIT RISK	12 Months Ended
	Sep. 30, 2018
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 guaranties. 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 $11.2 at September 30, 2018 ( $3.7 reflecting netting arrangements). Spire Marketing’s accounts receivable attributable to utility companies and their marketing affiliates comprised $96.1 of total accounts receivable at September 30, 2018 ( $89.7 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, 2018 , the amounts included in accounts receivable from Spire Marketing’s five largest counterparties (in terms of net accounts receivable exposure) totaled $51.3 ( $50.6 reflecting netting arrangements). Three of these five counterparties are investment-grade rated integrated utilities. The fourth is an investment-grade rated wholesale power provider. The fifth is not rated, but each of its owners is investment-grade.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Spire The Company’s provision (benefit) for income taxes during the fiscal years ended September 30, 2018 , 2017 , and 2016 was as follows: 2018 2017 2016 Federal Current $ — $ 0.1 $ 0.1 Deferred (22.7 ) 67.7 62.0 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current 2.2 0.5 0.6 Deferred (5.8 ) 9.5 7.0 Total income tax (benefit) expense $ (26.5 ) $ 77.6 $ 69.5 The Company’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2018 2017 2016 Federal income tax statutory rate 24.5 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 3.4 2.8 2.8 Certain expenses capitalized on books and deducted on tax return (2.3 ) (2.3 ) (3.4 ) Taxes related to prior years (0.4 ) (0.9 ) (0.2 ) Tax law changes (35.9 ) — — Amortization of excess deferred taxes (1.8 ) — — Other items – net * (1.6 ) (2.2 ) (1.7 ) Effective income tax rate (14.1 )% 32.4 % 32.5 % * 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 were as follows: 2018 2017 Deferred tax assets: Reserves not currently deductible $ 25.9 $ 31.5 Pension and other postretirement benefits 75.6 58.6 Operating losses 162.7 169.6 Regulatory amount due to customers, net 41.8 — Other 8.2 26.0 Deferred tax assets 314.2 285.7 Less: valuation allowance 1.4 0.5 Total deferred tax assets 312.8 285.2 Deferred tax liabilities: Relating to property 518.3 728.3 Regulatory pension and other postretirement benefits 117.1 108.0 Deferred gas costs 2.3 30.6 Other** 110.9 125.8 Total deferred tax liabilities 748.6 992.7 Net deferred tax liability $ 435.8 $ 707.5 ** Other consists primarily of Goodwill related liabilities. The Tax Cuts and Jobs Act (“TCJA”) was signed into law on December 22, 2017, with an effective date of January 1, 2018, for substantially all of the provisions. This comprehensive act includes significant reform of the current income tax code including changes in the calculation for business entities and a reduction in the corporate federal income tax rate from 35% to 21%. The specific provisions related to regulated public utilities in the TCJA generally allow for the continued deductibility of interest expense, the elimination of full expensing for tax purposes of certain property acquired in tax years beginning after January 1, 2018, and the continuation of certain rate normalization requirements for accelerated depreciation benefits. Missouri Senate Bill (“S.B.”) 884 was signed into law on June 1, 2018. S.B. 884 reduces the corporate income tax rate from 6.25% to 4.0% for tax years beginning on or after January 1, 2020, among other legislative changes. The impact of S.B. 884 is not material to the consolidated financial statements. ASC Topic 740, Income Taxes, requires that the effects of changes in tax laws be recognized in the period in which the new law is enacted. It also requires deferred tax assets and liabilities to be measured at the enacted tax rate expected to apply when temporary differences are to be realized or settled. For the Company’s regulated entities, the changes in deferred taxes related to the regulated operations are recorded as either an offset to or creation of a regulatory asset or liability and may be subject to refund to customers in future periods. The changes in deferred taxes that are not associated with rate making (including all changes for the Company’s non-regulated operations) are recorded as adjustments to deferred tax expense or benefit. The Company has recorded TCJA impacts and reflected those amounts in the September 30, 2018 financial statements. The amounts recorded are based on information known and reasonable estimates used as of that date, but are subject to change based on further actions of regulators. The items recorded include the impact of the federal income tax rate reduction and the revaluation of the deferred tax assets and liabilities. In fiscal 2018, the MoPSC Amended Report and Order took effect and the estimated excess accumulated deferred income tax began to be returned to customers in rates. The amount being returned is estimated with a tracker established to defer the difference from the estimated amounts to the actual amounts once the actual amounts have been calculated. During fiscal 2018, excess accumulated deferred taxes of $3.5 were returned. The total amounts recorded, before reduction for amounts returned to customers, for the year ended September 30, 2018, are presented in the table below. Adjustment to deferred tax liabilities $ (318.3 ) Adjustment to deferred income tax expense (75.0 ) Adjustment to regulatory assets (75.9 ) Adjustment to regulatory liabilities 167.4 As indicated in Note 1 , Summary of Significant Accounting Policies, the Company’s regulated operations accounting for income taxes is impacted by ASC Topic 980, Regulated Operations . Reductions in deferred income tax balances due to the reduction in the corporate income tax rate will result in amounts previously collected from utility customers for these deferred taxes to be refundable to such customers, generally through reductions in future rates. The TCJA includes provisions that stipulate how these excess deferred taxes are to be passed back to customers for certain accelerated tax depreciation benefits. Potential refunds of other deferred taxes will be determined by state regulators. 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 had federal and state loss carryforwards of approximately $711.9 at September 30, 2018 . The Company also had contribution carryforwards of approximately $12.9 at September 30, 2018 . 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 2019. The Company had a valuation allowance of $1.4 , 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 $2.4 that begin to expire in 2020, as well as a capital loss carryforward of $0.4 that expires in 2022. 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 to the extent the recognition of the benefit would impact the operating loss carryforward, pursuant to ASU 2013-11. In addition, pursuant to the TCJA, the deferred tax asset for a net operating loss carryforward was revalued based on the federal tax law change. The following table presents a reconciliation of the beginning and ending balances of the Company’s unrecognized tax benefits: 2018 2017 2016 Unrecognized tax benefits, beginning of year $ 11.0 $ 10.0 $ 7.1 Decrease related to tax law changes (4.0 ) — — Increases related to tax positions taken in current year 1.2 2.4 3.4 Reductions due to lapse of applicable statute of limitations (0.1 ) (1.4 ) (0.5 ) Unrecognized tax benefits, end of year $ 8.1 $ 11.0 $ 10.0 The amount of unrecognized tax benefits which, if recognized, would affect the Company’s effective tax rate were $3.9 and $5.1 as of September 30, 2018 and 2017 , 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, 2018 and 2017 , interest accrued associated with the Company’s uncertain tax positions was de minimis, and no penalties were accrued. The Company is subject to 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 Spire EnergySouth acquisition, tax returns for calendar years 2014 and 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 (benefit) for income taxes during the fiscal years ended September 30, 2018 , 2017 , and 2016 was as follows: 2018 2017 2016 Federal Current $ — $ — $ — Deferred (26.1 ) 42.0 37.5 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current — — 0.1 Deferred (6.3 ) 5.7 8.0 Total income tax (benefit) expense $ (32.6 ) $ 47.5 $ 45.4 Spire Missouri’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2018 2017 2016 Federal income tax statutory rate 24.5 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 3.4 2.8 2.8 Certain expenses capitalized on books and deducted on tax return (4.6 ) (3.5 ) (4.8 ) Taxes related to prior years (0.7 ) (1.4 ) (0.2 ) Tax law changes (50.3 ) — — Amortization of excess deferred taxes (3.6 ) — — Other items – net * (2.5 ) (3.3 ) (2.8 ) Effective income tax rate (33.8 )% 29.6 % 30.0 % * 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 were as follows: 2018 2017 Deferred tax assets: Reserves not currently deductible $ 20.0 $ 25.3 Pension and other postretirement benefits 71.9 52.7 Deferred gas costs 0.5 — Operating losses 65.2 52.0 Regulatory amount due to customers 38.0 — Deferred tax assets 195.6 130.0 Less: valuation allowance 1.4 0.5 Total deferred tax assets 194.2 129.5 Deferred tax liabilities: Relating to utility property 372.6 563.2 Regulatory pension and other postretirement benefits 113.4 108.0 Deferred gas costs — 25.0 Other 69.2 57.1 Total deferred tax liabilities 555.2 753.3 Net deferred tax liability $ 361.0 $ 623.8 Spire files a consolidated federal income tax 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. Spire Missouri has recorded TCJA impacts and reflected those amounts in the September 30, 2018 financial statements. The amounts recorded are based on information known and reasonable estimates used as of that date, but are subject to change based on further actions of regulators. The items recorded include the impact of the federal income tax rate reduction and the revaluation of the deferred tax assets and liabilities. In fiscal 2018, the MoPSC Amended Report and Order took effect and the estimated excess accumulated deferred income tax began to be returned to customers in rates. The amount being returned is estimated with a tracker established to defer the difference from the estimated amounts to the actual amounts once the actual amounts have been calculated. During fiscal 2018, excess accumulated deferred taxes of $3.5 were returned. S.B. 884, signed into law on June 1, 2018, reduces the corporate income tax rate from 6.25% to 4.0% for tax years beginning on or after January 1, 2020, among other legislative changes. The impact of S.B. 884 is not material to the financial statements. The total amounts recorded, before reduction for amounts returned to customers, for the year ended September 30, 2018, are presented in the table below. Adjustment to deferred tax liabilities $ (285.3 ) Adjustment to deferred income tax expense (57.0 ) Adjustment to regulatory assets (78.1 ) Adjustment to regulatory liabilities 150.2 As indicated in Note 1 , Summary of Significant Accounting Policies, the Company’s regulated operations accounting for income taxes is impacted by ASC Topic 980, Regulated Operations . Reductions in deferred income tax balances due to the reduction in the corporate income tax rate will result in amounts previously collected from utility customers for these deferred taxes to be refundable to such customers, generally through reductions in future rates. The TCJA includes provisions that stipulate how these excess deferred taxes are to be passed back to customers for certain accelerated tax depreciation benefits. Potential refunds of other deferred taxes will be determined by state regulators. 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 had federal and state loss carryforwards of approximately $309.2 at September 30, 2018 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 had contribution carryforwards of approximately $10.9 at September 30, 2018 . The loss carryforwards begin to expire in fiscal 2035 for federal and state purposes. The contribution carryforwards begin to expire in fiscal 2019. Spire Missouri had a valuation allowance of $1.4 , 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, pursuant to ASU 2013-11. In addition, pursuant to the TCJA, the deferred tax asset for a net operating loss carryforward was revalued based on the federal tax law change. The following table presents a reconciliation of the beginning and ending balances of Spire Missouri unrecognized tax benefits: 2018 2017 2016 Unrecognized tax benefits, beginning of year $ 10.7 $ 9.7 $ 6.9 Decrease related to tax law changes (4.0 ) — — Increases related to tax positions taken in current year 1.1 2.4 3.3 Reductions due to lapse of applicable statute of limitations — (1.4 ) (0.5 ) Unrecognized tax benefits, end of year $ 7.8 $ 10.7 $ 9.7 The amount of unrecognized tax benefits, which, if recognized, would affect Spire Missouri’s effective tax rate were $3.6 and $4.8 as of September 30, 2018 and 2017 , 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, 2018 and 2017 , no interest or penalties were accrued associated with Spire Missouri’s uncertain tax positions. Spire Missouri is subject to 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, 2018 , 2017 , and 2016 , was as follows: 2018 2017 2016 Federal Current $ — $ — $ (0.8 ) Deferred 81.5 31.6 29.4 State and local Current — — — Deferred 0.1 4.2 3.8 Total income tax expense $ 81.6 $ 35.8 $ 32.4 Spire Alabama’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2018 2017 2016 Federal income tax statutory rate 24.5 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 3.8 2.8 2.8 Tax law change 70.0 — — Other items – net 0.1 0.3 0.1 Effective income tax rate 98.4 % 38.1 % 37.9 % Spire Alabama’s significant items comprising the net deferred tax asset reported in the Balance Sheets as of September 30 were as follows: 2018 2017 Deferred tax assets: Reserves not currently deductible $ 5.3 $ 6.0 Pension and other postretirement benefits — 4.4 Goodwill 129.6 214.4 Operating losses 86.0 88.3 Total deferred tax assets 220.9 313.1 Deferred tax liabilities: Relating to utility property 111.9 119.3 Pension and other postretirement benefits 1.8 — Other 5.4 8.2 Total deferred tax liabilities 119.1 127.5 Net deferred tax asset $ 101.8 $ 185.6 Spire files a consolidated federal income tax 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. Spire Alabama has recorded TCJA impacts and reflected those amounts in the September 30, 2018 financial statements. The amounts recorded are based on information known and reasonable estimates used as of that date, but are subject to change based on further actions of regulators. The items recorded include the impact of the federal income tax rate reduction and the revaluation of the deferred tax assets and liabilities. The total amounts recorded, before reduction for amounts returned to customers, for the year ended September 30, 2018, are presented in the table below. Adjustment to deferred tax assets $ (61.0 ) Adjustment to deferred income tax expense 58.8 Adjustment to regulatory assets 2.2 As indicated in Note 1 , Summary of Significant Accounting Policies, the Company’s regulated operations accounting for income taxes is impacted by ASC Topic 980, Regulated Operations . Reductions in deferred income tax balances due to the reduction in the corporate income tax rate will result in amounts previously collected from utility customers for these deferred taxes to be refundable to such customers, generally through reductions in future rates. The TCJA includes provisions that stipulate how these excess deferred taxes are to be passed back to customers for certain accelerated tax depreciation benefits. Potential refunds of other deferred taxes will be determined by state regulators. 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 had federal and state loss carryforwards of approximately $342.6 at September 30, 2018 . 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 2018, 2017, and 2016. Spire Alabama is subject to federal income tax as well as income tax in various state and local jurisdictions. Energen’s tax return for 2014, which includes Spire Alabama, remains open to the statute of limitations for federal purposes as a result of an IRS examination. No state tax returns for periods in which Spire Alabama was owned by Energen are open to the statute of limitations. The impact of any adjustments made to this return by the IRS would be addressed by the indemnification provisions of the 2014 stock purchase agreement with Energen.

PENSION PLANS AND OTHER POSTRET

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS	12 Months Ended
	Sep. 30, 2018
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 covering employees 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, the employees of Spire Alabama and 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 U.S. 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 U.S. 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 2018 2017 2016 2018 2017 2016 2018 2017 2016 Service cost – benefits earned during the period $ 20.2 $ 20.5 $ 15.3 $ 12.7 $ 12.7 $ 10.0 $ 6.4 $ 6.2 $ 5.3 Interest cost on projected benefit obligation 27.4 27.9 28.0 19.5 19.5 21.7 5.5 6.1 6.3 Expected return on plan assets (37.0 ) (38.5 ) (34.9 ) (27.2 ) (28.1 ) (26.7 ) (6.5 ) (7.2 ) (8.2 ) Amortization of prior service cost (credit) (0.9 ) 1.0 0.4 0.9 1.0 0.4 (1.8 ) — — Amortization of actuarial loss 10.9 12.5 8.0 9.4 10.7 7.9 1.5 1.8 0.1 Loss on lump-sum settlements and curtailments 18.6 17.9 3.3 16.1 13.5 — 2.4 4.6 3.3 Special termination benefits — 0.9 1.6 — — 1.6 — — — Subtotal 39.2 42.2 21.7 31.4 29.3 14.9 7.5 11.5 6.8 Regulatory adjustment 37.4 (2.4 ) 17.8 32.1 (4.1 ) 11.7 4.5 1.8 6.1 Net pension cost $ 76.6 $ 39.8 $ 39.5 $ 63.5 $ 25.2 $ 26.6 $ 12.0 $ 13.3 $ 12.9 Other changes in plan assets and pension benefit obligations recognized in other comprehensive income or loss include the following: Spire Spire Missouri Spire Alabama 2018 2017 2016 2018 2017 2016 2018 2017 2016 Current year actuarial (gain) loss $ (1.4 ) $ 14.1 $ 46.8 $ 2.2 $ 14.8 $ 21.6 $ (0.6 ) $ 3.3 $ 25.2 Amortization of actuarial loss (10.9 ) (12.5 ) (8.0 ) (9.4 ) (10.7 ) (7.9 ) (1.5 ) (1.8 ) (0.1 ) Acceleration of loss recognized due to settlement (18.5 ) (18.2 ) (3.3 ) (16.1 ) (13.5 ) — (2.4 ) (4.5 ) (3.3 ) Current year service (credit) cost (0.1 ) — 5.0 — — 5.0 — — — Current year prior year service cost — (20.7 ) — — — — — (20.7 ) — Transfer due to merger 0.1 — — 0.1 — — — — — Amortization of prior service cost (2.9 ) (1.0 ) (0.4 ) (0.9 ) (1.0 ) (0.4 ) — — — Amortization of transition asset 1.8 — — — — — 1.8 — — Subtotal (31.9 ) (38.3 ) 40.1 (24.1 ) (10.4 ) 18.3 (2.7 ) (23.7 ) 21.8 Regulatory adjustment 31.6 38.0 (39.8 ) 23.8 10.1 (18.0 ) 2.7 23.7 (21.8 ) Total recognized in OCI $ (0.3 ) $ (0.3 ) $ 0.3 $ (0.3 ) $ (0.3 ) $ 0.3 $ — $ — $ — 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 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, 2018 , requiring re-measurement of the obligation under those plans using updated census data and assumptions for discount rate and mortality. For the remeasurements, the discount rates for the Missouri plans were updated to 4.20% and 4.15% at June 30, 2018 (from 3.70% and 3.75% at September 30, 2017), and the discount rate for the Alabama plan was updated to 4.20% (from 3.65% ). Lump-sum payments recognized as settlements during fiscal years 2018 , 2017 , and 2016 were $82.8 ( $65.5 attributable to Spire Missouri and $17.3 to Spire Alabama), $62.2 ( $43.5 attributable to Spire Missouri and $18.7 to Spire Alabama), and $16.6 (attributable 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. Up to April 18, 2018, the recovery in rates for Spire Missouri East’s qualified pension plan was based on an annual allowance of $15.5 effective January 1, 2011. The recovery in rates for Spire Missouri West’s qualified pension plan was based on an annual allowance of approximately $9.9 effective February 20, 2010. Effective April 19, 2018, the pension cost for Spire Missouri West included in customer rates was reduced from $9.9 to $5.5 per year, the pension cost included in the Spire Missouri East customer rates was increased from $15.5 to $29.0 per year. Over an amortization period of eight years , Spire Missouri East rates will also include the amortization of $173.0 of assets for pension and other postretirement benefits, and Spire Missouri West rates will be reduced by the amortization of a $26.2 net liability for pension and other postretirement benefits. These changes are discussed further in Note 14 , Regulatory Matters. 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 2018 2017 2018 2017 2018 2017 Benefit obligation, beginning of year $ 748.8 $ 794.7 $ 539.6 $ 560.0 $ 148.2 $ 174.3 Service cost 20.2 20.5 12.7 12.7 6.4 6.2 Interest cost 27.4 27.9 19.5 19.5 5.5 6.1 Actuarial (gain) loss (34.9 ) (0.9 ) (26.0 ) (0.5 ) (3.8 ) 1.6 Plan amendments (2.0 ) (20.7 ) — — — (20.7 ) Plan mergers — — (0.3 ) — — — Settlement loss 7.6 14.6 7.6 12.2 — 2.4 Special termination benefits — 0.9 — — — — Settlement benefits paid (82.8 ) (62.2 ) (65.5 ) (43.5 ) (17.3 ) (18.7 ) Regular benefits paid (19.7 ) (26.0 ) (14.3 ) (20.8 ) (2.7 ) (3.0 ) Benefit obligation, end of year $ 664.6 $ 748.8 $ 473.3 $ 539.6 $ 136.3 $ 148.2 Accumulated benefit obligation, end of year $ 636.0 $ 701.4 $ 446.5 $ 500.4 $ 134.5 $ 142.8 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 2018 2017 2018 2017 2018 2017 Fair value of plan assets, beginning of year $ 531.6 $ 540.5 $ 385.9 $ 395.7 $ 97.9 $ 100.0 Actual return on plan assets 11.2 38.0 6.4 25.1 3.3 7.7 Employer contributions 58.9 41.3 36.9 29.4 20.1 11.9 Divestitures — — (0.3 ) — — — Settlement benefits paid (82.8 ) (62.2 ) (65.5 ) (43.5 ) (17.3 ) (18.7 ) Regular benefits paid (19.7 ) (26.0 ) (14.3 ) (20.8 ) (2.7 ) (3.0 ) Fair value of plan assets, end of year $ 499.2 $ 531.6 $ 349.1 $ 385.9 $ 101.3 $ 97.9 Funded status of plans, end of year $ (165.4 ) $ (217.2 ) $ (124.2 ) $ (153.7 ) $ (35.0 ) $ (50.3 ) The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2018 2017 2018 2017 2018 2017 Current liabilities $ (0.6 ) $ (0.5 ) $ (0.6 ) $ (0.5 ) $ — $ — Noncurrent liabilities (164.8 ) (216.7 ) (123.6 ) (153.2 ) (35.0 ) (50.3 ) Total $ (165.4 ) $ (217.2 ) $ (124.2 ) $ (153.7 ) $ (35.0 ) $ (50.3 ) 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 2018 2017 2018 2017 2018 2017 Net actuarial loss $ 132.1 $ 163.0 $ 102.8 $ 126.2 $ 36.4 $ 40.9 Prior service (credit) cost (14.4 ) (13.4 ) 6.4 7.3 (18.8 ) (20.7 ) Subtotal 117.7 149.6 109.2 133.5 17.6 20.2 Adjustments for amounts included in regulatory assets (115.5 ) (147.1 ) (107.0 ) (131.0 ) (17.6 ) (20.2 ) Total $ 2.2 $ 2.5 $ 2.2 $ 2.5 $ — $ — At September 30, 2018 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic pension cost during fiscal 2019 : Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ 9.2 $ 8.6 $ 0.8 Amortization of prior service (credit) cost (0.9 ) 0.9 (1.8 ) Subtotal 8.3 9.5 (1.0 ) Regulatory adjustment (8.1 ) (9.3 ) 1.0 Total $ 0.2 $ 0.2 $ — The assumptions used to calculate net periodic pension costs for Spire Missouri are as follows: 2018 2017 2016 Weighted average discount rate - Spire Missouri East plan 3.75% 3.50% 4.40% Weighted average discount rate - Spire Missouri West plan 3.70% 3.50% 4.50% 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: 2018 2017 2016 Weighted average discount rate 3.65%/3.70% 3.45%/3.50% 4.25%/4.30% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 7.25% 7.25% 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 benefit obligations are as follows: 2018 2017 Weighted average discount rate - Spire Missouri East plan 4.30% 3.75% Weighted average discount rate - Spire Missouri West plan 4.35% 3.70% Weighted average discount rate - Spire Alabama plans 4.35% 3.65%/3.70% 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 2018 2017 2018 2017 2018 2017 Projected benefit obligation $ 664.6 $ 748.8 $ 473.3 $ 539.6 $ 136.3 $ 148.2 Accumulated benefit obligation 636.0 701.4 446.5 500.4 134.5 142.8 Fair value of plan assets 499.2 531.6 349.1 385.9 101.3 97.9 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 2018 2018 2017 2017 Equity markets 56.4 % 55.3 % 56.4 % 56.8 % Debt securities 43.6 % 42.4 % 43.6 % 42.0 % Cash equivalents — % 2.3 % — % 1.2 % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Alabama 2018 2018 2017 2017 Equity markets 60.0 % 59.4 % 60.0 % 58.5 % Debt securities 29.0 % 28.6 % 29.0 % 28.7 % Other* 11.0 % 12.0 % 11.0 % 12.8 % 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, U.S. 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: 2019 2020 2021 2022 2023 2024- 2028 Spire $ 63.0 $ 63.6 $ 60.0 $ 58.4 $ 57.1 $ 266.4 Spire Missouri 50.3 50.2 46.0 43.8 41.9 184.8 Spire Alabama 10.0 10.7 11.2 11.8 12.3 65.5 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 2019 are anticipated to be $27.1 into the qualified trusts, and $0.5 into the non-qualified plans. Spire Alabama had no required contributions to the qualified pension plans during 2018 or 2017, and 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 2018 and 2017, Spire Alabama made discretionary contributions to the qualified pension plans totaling $20.1 and $11.9 , respectively; none are expected in fiscal 2019. 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 2018 2017 2016 2018 2017 2016 2018 2017 2016 Service cost – benefits earned during the period $ 9.4 $ 11.0 $ 10.9 $ 9.0 $ 10.4 $ 10.6 $ 0.2 $ 0.3 $ 0.3 Interest cost on accumulated postretirement benefit obligation 8.6 8.6 10.2 6.9 6.8 8.1 1.5 1.6 2.1 Expected return on plan assets (13.9 ) (13.6 ) (13.5 ) (9.6 ) (9.0 ) (8.5 ) (4.1 ) (4.4 ) (5.0 ) Amortization of prior service cost (credit) (0.1 ) — 0.3 0.3 0.2 0.3 (0.4 ) (0.2 ) — Amortization of actuarial loss (gain) 0.8 2.5 3.6 0.9 2.6 3.8 (0.1 ) (0.1 ) (0.2 ) Special termination benefits — — 2.6 — — 2.6 — — — Subtotal 4.8 8.5 14.1 7.5 11.0 16.9 (2.9 ) (2.8 ) (2.8 ) Regulatory adjustment 2.2 (3.2 ) (6.6 ) 3.9 (1.5 ) (4.8 ) (1.8 ) (1.8 ) (1.8 ) Net postretirement benefit cost $ 7.0 $ 5.3 $ 7.5 $ 11.4 $ 9.5 $ 12.1 $ (4.7 ) $ (4.6 ) $ (4.6 ) Other changes in plan assets and postretirement benefit obligations recognized in OCI include the following: Spire Spire Missouri Spire Alabama 2018 2017 2016 2018 2017 2016 2018 2017 2016 Current year actuarial (gain) loss $ (45.1 ) $ (34.1 ) $ 0.8 $ (47.1 ) $ (28.5 ) $ 1.4 $ 1.6 $ (4.5 ) $ (0.6 ) Amortization of actuarial (loss) gain (0.8 ) (2.5 ) (3.6 ) (0.9 ) (2.6 ) (3.8 ) 0.1 0.1 0.2 Current year prior service credit — (1.4 ) (1.8 ) — — — — (1.4 ) (1.8 ) Amortization of prior service (cost) credit 0.1 — (0.3 ) (0.3 ) (0.2 ) (0.3 ) 0.4 0.2 — Subtotal (45.8 ) (38.0 ) (4.9 ) (48.3 ) (31.3 ) (2.7 ) 2.1 (5.6 ) (2.2 ) Regulatory adjustment 45.8 38.0 4.9 48.3 31.3 2.7 (2.1 ) 5.6 2.2 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. Up to April 18, 2018, the recovery in rates for Spire Missouri’s postretirement benefit plans is based on an annual allowance of $9.5 effective January 1, 2011. Effective April 19, 2018, the allowance was reduced to $8.6 . This change is discussed further in Note 14 , Regulatory Matters. 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 2018 2017 2018 2017 2018 2017 Benefit obligation, beginning of year $ 238.5 $ 259.2 $ 192.5 $ 207.9 $ 40.6 $ 45.4 Service cost 9.4 11.0 9.0 10.4 0.2 0.3 Interest cost 8.6 8.6 6.9 6.8 1.5 1.6 Actuarial (gain) loss (37.5 ) (22.1 ) (41.1 ) (20.9 ) 3.1 — Plan amendments — (1.4 ) — — — (1.4 ) Curtailments — 0.4 — — — — Retiree drug subsidy program 0.2 0.3 0.1 0.3 0.1 — Benefits paid (11.1 ) (17.5 ) (8.6 ) (12.0 ) (2.4 ) (5.3 ) Benefit obligation, end of year $ 208.1 $ 238.5 $ 158.8 $ 192.5 $ 43.1 $ 40.6 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 2018 2017 2018 2017 2018 2017 Fair value of plan assets at beginning of year $ 265.5 $ 246.4 $ 174.9 $ 159.7 $ 86.4 $ 82.8 Actual return on plan assets 21.5 26.2 15.6 16.8 5.6 8.9 Employer contributions 7.6 10.4 7.6 10.4 — — Benefits paid (11.1 ) (17.5 ) (8.6 ) (12.0 ) (2.4 ) (5.3 ) Fair value of plan assets, end of year $ 283.5 $ 265.5 $ 189.5 $ 174.9 $ 89.6 $ 86.4 Funded status of plans, end of year $ 75.4 $ 27.0 $ 30.7 $ (17.6 ) $ 46.5 $ 45.8 The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2018 2017 2018 2017 2018 2017 Current assets $ — $ 1.4 $ — $ 1.4 $ — $ — Noncurrent assets 92.0 47.0 45.5 1.2 46.5 45.8 Current liabilities (0.5 ) (0.4 ) (0.5 ) (0.4 ) — — Noncurrent liabilities (16.1 ) (21.0 ) (14.3 ) (19.8 ) — — Total $ 75.4 $ 27.0 $ 30.7 $ (17.6 ) $ 46.5 $ 45.8 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 2018 2017 2018 2017 2018 2017 Net actuarial loss (gain) $ (44.4 ) $ 1.5 $ (35.7 ) $ 12.3 $ (8.0 ) $ (9.7 ) Prior service credit (6.6 ) (6.6 ) (4.0 ) (3.7 ) (2.6 ) (2.9 ) Subtotal (51.0 ) (5.1 ) (39.7 ) 8.6 (10.6 ) (12.6 ) Adjustments for amounts included in regulatory assets 51.0 5.1 39.7 (8.6 ) 10.6 12.6 Total $ — $ — $ — $ — $ — $ — At September 30, 2018 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic postretirement benefit cost during fiscal 2019: Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ (0.5 ) $ (0.5 ) $ — Amortization of prior service (credit) cost (0.1 ) 0.3 (0.4 ) Subtotal (0.6 ) (0.2 ) (0.4 ) Regulatory adjustment 0.6 0.2 0.4 Total $ — $ — $ — The assumptions used to calculate net periodic postretirement benefit costs for Spire Missouri are as follows: 2018 2017 2016 Weighted average discount rate - Spire Missouri East plans 3.60% 3.15% 4.00% Weighted average discount rate - Spire Missouri West plans 3.60% 3.45% 4.30% 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% 5.75%/7.75% 6.00%/7.75% Expected long-term rate of return on plan assets - Spire Missouri West plans 5.75% 5.50% 4.75% The assumptions used to calculate net periodic postretirement benefit costs for Spire Alabama are as follows: 2018 2017 2016 Weighted average discount rate 3.80% 3.60% 4.50% Expected long-term rate of return on plan assets 3.75%/6.00% 4.00%/6.25% 4.50%/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 accumulated postretirement benefit obligations are as follows: 2018 2017 Weighted average discount rate - Spire Alabama plans 4.30% 3.80% Weighted average discount rate - Spire Missouri East plans 4.30% 3.60% Weighted average discount rate - Spire Missouri West plans 4.30% 3.60% 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: 2018 2017 Medical cost trend assumed for next year - Spire Missouri 7.00% 7.25% Medical cost trend assumed for next year - Spire Alabama 7.00% 7.25% 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 2025 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 $ 1.4 $ (1.3 ) $ 1.2 $ (1.1 ) $ 0.1 $ (0.1 ) Accumulated postretirement benefit obligation 8.4 (7.7 ) 6.0 (5.6 ) 1.6 (1.5 ) 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 2018 Actual 2017 Actual Equity securities 60.0 % 58.8 % 59.0 % Debt securities 40.0 % 39.1 % 39.4 % Other (cash and cash equivalents held to make benefit payments) — % 2.1 % 1.6 % Total 100.0 % 100.0 % 100.0 % Spire Alabama Target 2018 Actual 2017 Actual Equity securities 60.0 % 60.0 % 60.1 % Debt securities 40.0 % 40.0 % 39.9 % 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. The Utilities 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 U.S. 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: 2019 2020 2021 2022 2023 2024- 2028 Spire $ 14.2 $ 15.3 $ 16.3 $ 16.9 $ 17.9 $ 93.9 Spire Missouri 10.8 11.8 12.8 13.4 14.3 76.4 Spire Alabama 3.0 3.1 3.1 3.1 3.2 15.1 The Utilities’ 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 2019 are anticipated to be $1.9 to the qualified trusts and $0.5 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 2019 . Other Plans Spire Services Inc. sponsors a 401(k) plan that cover substantially all employees of Spire Inc. and its subsidiaries. The plan allows employees to contribute a portion of their base pay in accordance with specific guidelines. The cost of the defined contribution plan for Spire Inc. totaled $12.2 , $11.5 , and $10.5 for fiscal years 2018 , 2017 , and 2016 , respectively. Spire Missouri provides a match of such contributions within specific limits. The cost of the defined contribution plan for Spire Missouri amounted to $9.0 , $8.4 , and $8.2 for fiscal years 2018 , 2017 , and 2016 , respectively. Spire Alabama also provides a match of employee contributions within specific limits. The cost of the defined contribution plan for Spire Alabama amounted to $3.0 , $2.7 , and $2.3 for fiscal years 2018 , 2017 , and 2016 , 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, 2018 Cash and cash equivalents $ 50.6 $ — $ — $ 50.6 Equity mutual funds - U.S. 42.7 21.2 — 63.9 Equity mutual funds - international 20.7 4.1 — 24.8 Debt securities: U.S. bond mutual funds 35.8 64.9 — 100.7 U.S. government 31.7 5.6 — 37.3 U.S. corporate 152.1 — — 152.1 U.S. municipal 3.6 3.0 — 6.6 International 43.9 7.0 — 50.9 Derivatives and margin (payable) (0.8 ) — — (0.8 ) 103-12 Direct Filing Entities — 13.1 — 13.1 Total $ 380.3 $ 118.9 $ — $ 499.2 As of September 30, 2017 Cash and cash equivalents $ 37.3 $ — $ — $ 37.3 Equity mutual funds - U.S. 42.1 25.4 — 67.5 Equity mutual funds - international 37.4 11.2 — 48.6 Debt securities: U.S. bond mutual funds 34.4 68.5 — 102.9 U.S. government 33.2 4.5 — 37.7 U.S. corporate 183.7 — — 183.7 U.S. 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 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, 2018 Cash and cash equivalents $ 3.7 $ — $ — $ 3.7 U.S. stock/bond mutual funds 190.2 74.5 — 264.7 International fund — 15.1 — 15.1 Total $ 193.9 $ 89.6 $ — $ 283.5 As of September 30, 2017 Cash and cash equivalents $ 4.0 $ — $ — $ 4.0 U.S. 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 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, 2018 Cash and cash equivalents $ 35.2 $ — $ — $ 35.2 Equity mutual funds - U.S. — 8.4 — 8.4 Equity mutual funds - international — 4.1 — 4.1 Debt securities: U.S. bond mutual funds — 64.9 — 64.9 U.S. government 31.7 3.0 — 34.7 U.S. corporate 152.1 — — 152.1 U.S. municipal 3.6 3.0 — 6.6 International 43.9 — — 43.9 Derivatives and margin (payable) (0.8 ) — — (0.8 ) Total $ 265.7 $ 83.4 $ — $ 349.1 As of September 30, 2017 Cash and cash equivalents $ 31.7 $ — $ — $ 31.7 Equity mutual funds - U.S. — 11.9 — 11.9 Equity mutual funds - international — 5.7 — 5.7 Debt securities: U.S. bond mutual funds — 68.5 — 68.5 U.S. government 33.2 4.5 — 37.7 U.S. corporate 183.7 — — 183.7 U.S. 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 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, 2018 Cash and cash equivalents $ 3.5 $ — $ — $ 3.5 U.S. stock/bond mutual funds 186.0 — — 186.0 Total $ 189.5 $ — $ — $ 189.5 As of September 30, 2017 Cash and cash equivalents $ 3.9 $ — $ — $ 3.9 U.S. stock/bond mutual funds 171.0 — — 171.0 Total $ 174.9 $ — $ — $ 174.9 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) Sig

INFORMATION BY OPERATING SEGMEN

INFORMATION BY OPERATING SEGMENT	12 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
INFORMATION BY OPERATING SEGMENT	INFORMATION BY OPERATING SEGMENT 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, including utilizing 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 the construction and operation of a 65-mile FERC-regulated pipeline to deliver natural gas into eastern Missouri; • Spire Storage, providing physical natural gas storage services; 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. 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 fair value accounting and timing adjustments associated with energy-related transactions, the impacts of acquisition, divestiture and restructuring activities, and the largely non-cash impacts of other non-recurring or unusual items such as certain regulatory, legislative or GAAP standard-setting actions. In fiscal 2018, these items include the revaluation of deferred tax assets and liabilities due to the Tax Cuts and Jobs Act and the write-off of certain long-standing assets as a result of disallowances in our Missouri rate proceedings. Gas Utility Gas Marketing Other Eliminations Consolidated 2018 Revenues from external customers $ 1,888.0 $ 71.6 $ 5.4 $ — $ 1,965.0 Intersegment revenues 0.4 — 11.1 (11.5 ) — Total Operating Revenues 1,888.4 71.6 16.5 (11.5 ) 1,965.0 Operating Expenses Gas Utility Natural and propane gas 842.6 — — (72.5 ) 770.1 Other operation and maintenance 464.1 — — (8.5 ) 455.6 Depreciation and amortization 167.0 — — — 167.0 Taxes, other than income taxes 152.5 — — — 152.5 Total Gas Utility Operating Expenses 1,626.2 — — (81.0 ) 1,545.2 Gas Marketing and Other * — 37.8 32.8 69.5 140.1 Total Operating Expenses 1,626.2 37.8 32.8 (11.5 ) 1,685.3 Operating Income (Loss) $ 262.2 $ 33.8 $ (16.3 ) $ — $ 279.7 Net Economic Earnings (Loss) $ 183.1 $ 22.9 $ (22.3 ) $ — $ 183.7 Capital Expenditures $ 457.7 $ — $ 41.7 $ — $ 499.4 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 * Operating Expenses for “Gas Marketing and Other” include depreciation and amortization for Gas Marketing ( $0.0 for 2018 , $0.1 for 2017 , and $0.1 for 2016 ) and for Other ( $1.4 for 2018 , $0.5 for 2017 , and $0.5 for 2016 ). Total Assets at End of Year 2018 2017 2016 Gas Utility $ 5,606.7 $ 5,551.2 $ 5,184.7 Gas Marketing 295.3 246.2 205.0 Other 2,508.0 2,239.5 1,836.6 Eliminations (1,566.4 ) (1,490.2 ) (1,161.9 ) Total Assets $ 6,843.6 $ 6,546.7 $ 6,064.4 Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings 2018 2017 2016 Net Income $ 214.2 $ 161.6 $ 144.2 Adjustments, pre-tax: Missouri regulatory adjustments 30.6 — — Unrealized (gain) loss on energy-related derivatives (4.0 ) 6.0 (0.1 ) Lower of cost or market inventory adjustments — — 0.2 Realized gain on economic hedges prior to the sale of the physical commodity (0.3 ) (0.3 ) (1.6 ) Acquisition, divestiture and restructuring activities 13.6 4.0 9.2 Income tax effect of adjustments (10.3 ) (3.7 ) (2.8 ) Effect of the Tax Cuts and Jobs Act (60.1 ) — — Net Economic Earnings $ 183.7 $ 167.6 $ 149.1

REGULATORY MATTERS

REGULATORY MATTERS	12 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
REGULATORY MATTERS	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. The following regulatory assets and regulatory liabilities were reflected in the Balance Sheets as of September 30, 2018 and 2017 . 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 2018 2017 2018 2017 2018 2017 Regulatory Assets: Current: Pension and postretirement benefit costs $ 30.2 $ 42.2 $ 21.9 $ 34.9 $ 7.3 $ 7.2 Unamortized purchased gas adjustments 8.2 102.6 1.0 57.4 6.4 45.2 Other 34.4 30.7 7.8 3.3 12.5 12.2 Total Current Regulatory Assets 72.8 175.5 30.7 95.6 26.2 64.6 Noncurrent: Future income taxes due from customers 96.3 170.5 94.4 170.5 — — Pension and postretirement benefit costs 364.9 404.7 292.5 322.7 64.8 72.6 Cost of removal 133.4 123.3 — — 133.4 123.3 Unamortized purchased gas adjustments — 9.9 — 9.9 — — Energy efficiency 32.8 29.0 32.8 29.0 — — Other 42.4 53.7 21.4 25.7 3.3 1.1 Total Noncurrent Regulatory Assets 669.8 791.1 441.1 557.8 201.5 197.0 Total Regulatory Assets $ 742.6 $ 966.6 $ 471.8 $ 653.4 $ 227.7 $ 261.6 Regulatory Liabilities: Current: Rate Stabilization and Equalization (“RSE”) adjustment $ — $ 1.4 $ — $ — $ — $ 1.4 Refundable negative salvage 5.2 8.2 — — 5.2 8.2 Unamortized purchased gas adjustments 2.9 1.0 1.9 — — — Other 27.6 12.0 14.8 2.7 2.4 2.4 Total Current Regulatory Liabilities 35.7 22.6 16.7 2.7 7.6 12.0 Noncurrent: Deferred taxes due to customers 178.3 — 161.1 — — — Pension and postretirement benefit costs 27.8 32.2 — — 27.8 32.2 Refundable negative salvage — 4.1 — — — 4.1 Accrued cost of removal 63.6 83.8 39.8 54.5 — — Unamortized purchased gas adjustments 4.7 1.9 4.7 1.9 — — Other 80.2 35.2 69.3 24.8 3.5 3.3 Total Noncurrent Regulatory Liabilities 354.6 157.2 274.9 81.2 31.3 39.6 Total Regulatory Liabilities $ 390.3 $ 179.8 $ 291.6 $ 83.9 $ 38.9 $ 51.6 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 2018 2017 2018 2017 Pension and postretirement benefit costs $ 148.4 $ 170.5 $ 148.4 $ 170.5 Future income taxes due from customers 96.3 198.5 94.4 198.5 Other 15.1 11.3 15.1 11.3 Total Regulatory Assets Not Earning a Return $ 259.8 $ 380.3 $ 257.9 $ 380.3 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 other postretirement benefit costs could be as long as 20 years or longer, 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 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. • 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 Comprehensive 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. 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. Before April 19, 2018, the customer share of such income was 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, the customer share was 100%. 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% In the latest rate cases (discussed in the following paragraphs), the multiple sharing tiers and percentages were eliminated in favor of a single sharing percentage under which customers receive 75% (and Spire Missouri East and Spire Missouri West receive 25% ) of the net margins achieved as a result of such off-system sales and capacity releases. On March 7, 2018, the MoPSC issued an Amended Report and Order (the “Order”) in two general rate cases (docketed as GR-2017-0215 and GR-2017-0216) approving a base rate revenue requirement increase of $18.0 for Spire Missouri East and $15.2 for Spire Missouri West. The annualized Infrastructure System Replacement Surcharge (“ISRS”) amounts of $32.6 for Spire Missouri East and $16.4 for Spire Missouri West were reset to zero , resulting in a net decrease in revenues of $14.6 and $1.2 , respectively. These net amounts reflect decreases totaling approximately $33.0 resulting from the TCJA’s federal income tax rate reduction and a related allowance to return excess accumulated deferred income taxes to customers in accordance with Internal Revenue Service normalization requirements. Tariffs reflecting the Order went into effect on April 19, 2018. Included in the Order were updates to the treatment of pension and other postretirement benefits. Effective April 19, 2018, the pension cost for Spire Missouri West included in customer rates was reduced from $9.9 to $5.5 per year, the pension cost included in the Spire Missouri East customer rates was increased from $15.5 to $29.0 per year, and the annual allowance for health care postretirement plans for Spire Missouri East was reduced from $9.5 to $8.6 . Over a period of eight years , Spire Missouri East rates will also include the amortization of $173.0 of assets for pension and other postretirement benefits, and Spire Missouri West rates were reduced by the amortization of a $26.2 net liability for pension and other postretirement benefits. Certain provisions of the Order allow less future recovery of certain deferred or capitalized costs than estimated based upon previous rate proceedings. The Order denied recovery of $28.8 regulatory asset related to certain pension costs incurred prior to 1997. The Order also excluded from rate base certain incentive compensation costs totaling $6.9 , along with $1.8 of assets related to real estate sold in 2014. Rate case expenses totaling $0.9 were also disallowed. On April 25, 2018, Spire Missouri filed an appeal of the MoPSC’s decisions on the pension asset, the real estate sale, and rate case expense to Missouri’s Southern District Court of Appeals. Spire Missouri filed its initial brief in that court on October 17, 2018. Though the appeal is pending on these issues, management determined that the related assets, along with the incentive compensation exclusion, should be written down or off in connection with the preparation of the financial statements for the second quarter of 2018. For both Spire and Spire Missouri, the charges totaled $38.4 for the year ended September 30, 2018, and are included primarily in operation and maintenance expense on the statements of income and in other cash flows from operating activities on the statements of cash flows. The after-tax reduction to net income and earnings per share was $23.6 and $0.49 , respectively. The charges related to the long-standing pension and real estate assets, totaling $30.6 , are excluded in the determination of net economic earnings, as shown in Note 13 , Information by Operating Segment. On September 30, 2016, Spire Missouri filed ISRS cases for both Spire Missouri East and Spire Missouri West (the “2016 ISRS Cases”) and rates of $4.5 and $3.2 , respectively, became effective January 28, 2017. The Missouri Office of the Public Counsel (“OPC”) appealed the MoPSC’s decisions on the 2016 ISRS Cases to Missouri’s Western District Court of Appeals, arguing that a portion of these costs were ineligible because some plastic pipe was replaced along with the cast iron and bare steel. On February 3, 2017, Spire Missouri filed to increase its ISRS revenues in both its East and West service territories (the “2017 ISRS Cases”). The parties agreed to apply the outcome of the appeal in the 2016 ISRS Cases to the 2017 ISRS Cases, and $3.0 in rates for each of the two service territories became effective June 1, 2017. On November 21, 2017, the court reversed the MoPSC’s decision in the 2016 ISRS Cases to the extent costs were incurred to replace ISRS-ineligible plastic pipe and remanded the case to the MoPSC for further proceedings. On June 7, 2018, Spire Missouri filed to establish new ISRS rates in both its East and West divisions (the “2018 ISRS Cases”), requesting a $4.8 and $7.1 increase, respectively. On August 27, 2018, the MoPSC held a hearing on the plastics issue related to all of the above noted ISRS cases. On September 20, 2018, the MoPSC issued orders finding that Spire Missouri’s ISRS petitions in all three ISRS cases included ineligible costs related to the replacement of plastic pipe components. However, the MoPSC found that it lacked statutory authority to refund ineligible costs in the 2016 and 2017 ISRS Cases. On September 28, 2018 the MoPSC approved rates in the 2018 ISRS Cases of $2.6 for Spire Missouri East and $5.4 for Spire Missouri West, which became effective October 8, 2018. Spire Missouri and the OPC have both filed applications for rehearing in all of these ISRS cases. The MoPSC denied the rehearing for the 2016 and 2017 ISRS Cases on October 17, 2018, which OPC has appealed to the Western District Court. The MoPSC has not yet made a determination in the 2018 ISRS Cases. On September 20, 2018, the MoPSC approved financing authority for Spire Missouri in the amount of $500.0 , effective October 1, 2018, through September 30, 2021. Spire Alabama Spire Alabama’s rate schedules for natural gas distribution charges contain a GSA rider, established by the APSC 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. The APSC established the RSE rate-setting process in 1983. Effective January 1, 2014, Spire Alabama’s allowed range of return on average common equity was 10.5% to 10.95% with an adjusting point of 10.8% . Spire Alabama was 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. In October 2018, the APSC approved the renewal of RSE through September 30, 2022, with several modifications. Effective October 1, 2018, Spire Alabama’s allowed range of return on average common equity is 10.15% to 10.65% with an adjusting point of 10.4% . Spire Alabama is eligible to receive a performance-based adjustment of +/- 10 basis point to the return on equity adjusting point, based upon the terms of the newly approved Accelerated Infrastructure Modernization Program tariff. The 5-basis point adjustment for certain customer satisfaction criteria has been removed. Other modifications include an equity limitation as a percent of total capitalization from 56.5% to 55.5% and adjustments to the Cost Control Measure (“CCM”) as noted below. The RSE reduction for the September 30, 2017 quarterly point of test was $2.7 to bring the expected rate of return on average common equity at the end of the year to within the allowed range of return, effective December 1, 2017. As part of the annual update for RSE, on November 30, 2017, Spire Alabama filed an increase for rate year 2018 of $8.5 , which also became effective December 1, 2017. There was no RSE reduction in 2018 for the January 31, April 30, July 31 or September 30 quarterly points of test. Effective February 1, 2018, Spire Alabama rates were reduced by $12.8 to reflect the impact of tax reform under the TCJA on current income taxes. The inflation-based CCM, established by the APSC, allows for annual increases to operation and maintenance (“O&M”) expense. For the three years ended September 30, 2018, the CCM range was Spire Alabama’s 2007 actual rate year O&M expense inflation-adjusted using an index range based on the June Consumer Price Index For All Urban Consumers (“CPI-U”) each rate year plus or minus 1.75% . 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, 2018, Spire Alabama recorded a CCM benefit of $9.7 for rate year 2018, which will be reflected in rates effective December 1, 2018. The CCM benefit was $10.7 for rate year 2017 and $7.8 for rate year 2016. Effective October 1, 2018, the CCM will be calculated based upon O&M expense per customer and the O&M base year will be Spire Alabama’s actual 2018 O&M expense with an adjustment to that base in 2019 of 2/3 of the 2018 CCM differential (amount below the CCM range in 2018) and an adjustment in 2020 of 1/3 of the 2018 CCM differential , with no adjustment to the base in 2021 and 2022. Spire Alabama’s 2018 actual rate year O&M expense will be inflation adjusted using a new index range based on the June CPI-U each rate year plus or minus 1.50% . On June 28, 2010, the APSC approved a reduction in depreciation rates, effective June 1, 2010, and a regulatory liability to be recorded for Spire Alabama. Refunds from such negative salvage liability are being 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 2018, 2017, and 2016, NSR amounts returned to customers were approximately $7.2 , $6.3 , and $8.3 , respectively. As of September 30, 2018, $5.2 remains to be refunded through rate reductions effective December 1, 2018, through March 31, 2019. The APSC approved an ESR in 1998, which was subsequently modified and expanded in 2010. As currently approved, the ESR provides deferred treatment and recovery for the following: (1) extraordinary O&M expenses related to environmental response costs; (2) extraordinary O&M expenses related to self-insurance costs that exceed $1.0 per occurrence; (3) extraordinary O&M expenses, other than environmental response costs and self-insurance costs, resulting from a single force majeure event or multiple force majeure events greater than $0.3 and $0.4 , respectively, during a rate year; and (4) negative individual large commercial and industrial customer budget revenue variances that exceed $0.4 during a rate year. Charges to the ESR are subject to certain limitations which may disallow deferred treatment and which prescribe the timing of recovery. Funding to the ESR is provided as a reduction to the refundable negative salvage balance over its nine -year term beginning December 1, 2010. Subsequent to the nine -year period and subject to APSC authorization, Spire Alabama expects to be able to recover underfunded ESR balances over a five -year amortization period with an annual limitation of $0.7 . Amounts in excess of this limitation are deferred for recovery in future years. 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 October 2, 2018, the APSC approved an application for up to $90.0 of long-term debt financing. Spire In addition to those discussed above for Spire Missouri and Spire Alabama, Spire is affected by the following regulatory matters. Spire Gulf has similar rate regulation to Spire Alabama. The RSE allowed range of return on average common equity is 10.45% to 10.95% with an adjusting point of 10.7% . The CCM has the same return and similar recovery provisions when expenses exceed or are under a band of +/- 1.50% around the CPI-U inflated O&M per customer expense level from September 30, 2017, excluding expenses for pensions and gas bad debt. Additionally, it has a Cast Iron Main Replacement factor that provides an enhanced return on the pro-rata costs associated with cast iron main replacement for miles over 10 miles per year based on a 75% weighting for the equity content. Spire Gulf also has an ESR for negative revenue variances over $0.1 or a force majeure event expense of $0.1 (or two events that exceed $0.15 ), a Self Insurance Reserve for general liability coverage, and an Environmental Cost Recovery Factor that recovers 90% of prudently incurred costs for compliance with environmental laws, rules and regulations. It also has an APSC-approved intercompany revolving credit agreement with Spire to borrow in a principal amount not to exceed $50.0 , and to loan up to $25.0 . Spire Gulf’s rates were reduced $1.9 effective February 1, 2018, to reflect lower income taxes resulting from the TCJA. Spire Mississippi utilizes a formula rate-making process under the Rate Stabilization Adjustment (“RSA”) Rider. It is based on a formulaically derived return on equity (currently 9.34% ), and is updated on an annual basis if the equity return on an end of period rate base is beyond the allowed return on equity by 1.0% , with 75% of any shortfall back to the midpoint being put into a rate increase and 50% of any excess back to the midpoint resulting in a rate decrease. Updates may include known and measurable adjustments to historic costs from the 12 months ended June 30, submitted September 15 for an effective date of November 1, unless disputed by the Mississippi Public Utilities Staff, with any disputes to be resolved by the MSPSC by January 15 of the following year. In December 2015, a Supplemental Growth Rider (“SGR”) was approved for a 3 -year period to provide recovery of certain system expansion projects. On September 4, 2018, the SGR was extended to October 15, 2021. On April 10, 2018, the MSPSC approved an agreement between Spire Mississippi and the Mississippi Public Utility Staff settling its Rates Stabilization and Adjustments filing that was made on September 15, 2017, and included adjusting the federal income tax rate for the TCJA resulting in a $0.2 reduction in the annualized revenue requirement. New rates were effective May 1, 2018. In August 2018, FERC approved an order issuing a Certificate of Public Convenience and Necessity for the Spire STL Pipeline, and in November 2018, FERC issued a Notice to Proceed, allowing construction to begin. In fiscal 2018, the Company acquired and began integrating two neighboring natural gas storage facilities in Wyoming. Both storage facilities fall under FERC jurisdiction, and on July 9, 2018, the Company submitted an application with the FERC to abandon the cost-based tariff of the second facility and combine the operations under one FERC certificate with the market-based tariff of the first facility.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Sep. 30, 2018
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 2032, for the storage, transportation, and supply of natural gas. Minimum payments required under the contracts in place at September 30, 2018 are estimated at $1,240.9 , $572.4 and $286.5 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 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. Spire Missouri, Spire Alabama, Spire Marketing, and other Spire subsidiaries have other relatively minor rental arrangements that require minimum rental payments. 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 2018 2017 2016 2019 2020 2021 2022 2023 Later Total Spire $ 10.0 $ 9.7 $ 11.9 $ 9.7 $ 7.8 $ 6.7 $ 6.5 $ 6.5 $ 41.3 $ 78.5 Spire Missouri 3.6 4.8 4.3 1.3 0.6 0.3 0.1 — — 2.3 Spire Alabama 4.7 4.6 3.7 4.1 2.9 2.1 2.1 2.1 0.7 14.0 Amounts in the table above have not been reduced for sublease rentals. For Spire Alabama and Spire, annual sublease rentals were $2.1 for fiscal years 2018, 2017, and 2016, and minimum future rentals to be received in fiscal years 2019 and 2020 are $2.1 and $0.5 , respectively. Contingencies The Company and the Utilities account for contingencies, including environmental liabilities, 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. In addition to matters noted below, the Company and the Utilities are involved in other litigation, claims, and investigations arising in the normal course of business. Management, after discussion with counsel, believes 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. 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 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. To the extent costs are incurred associated with environmental remediation activities, the Utilities would request authority from their respective regulators to defer such costs (less any amounts received from insurance proceeds or as contributions from other potentially responsible parties (“PRPs”)) and collect them through future rates. Spire Missouri Spire Missouri has identified three former MGP sites in the city of St. Louis, Missouri (the “City”) where costs have been incurred and claims have been asserted. Spire Missouri has enrolled two of the sites in the Missouri Department of Natural Resources (“MDNR”) Brownfields/Voluntary Cleanup Program (“BVCP”). The third site is the result of a relatively new claim assertion by the United States Environmental Protection Agency (“EPA”) and such claim is currently being investigated. In conjunction with redevelopment of one of the sites, Spire Missouri and another former owner of the site entered into an agreement (the “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 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 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 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. To date, MDNR has not approved the agreement, so remedial investigation has not yet occurred. 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 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 requested more information from the EPA, some of which would 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 retains the right to seek potential reimbursements from them. On March 10, 2015, Spire Missouri received a Section 104(e) information request under CERCLA 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, including 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 Missouri Utilities’ 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, 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. 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 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, some of which remain pending. Spire Alabama 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 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 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 condition 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. Spire In addition to those discussed above for Spire Missouri and Spire Alabama, Spire is aware of the following contingent matters. Since April 2012, a total of 14 lawsuits encompassing more than 1,600 plaintiffs 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. All of the lawsuits have been substantially settled, with the exception of 13 individuals who rejected their settlement offers and whose claims remain pending. Those remaining claims allege nuisance, fraud and negligence causes of actions, and seek unspecified compensatory and punitive damages. A claim has been made against the insurance carriers requesting reimbursement for costs accrued in respect to this spill, and a related receivable has been recorded. 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. In February 2018, the Company was made aware of a complaint filed with the U.S. Department of Housing and Urban Development (“HUD”) by the South Alabama Center for Fair Housing and the National Community Reinvestment Coalition. The complaint alleges that the Company discriminated against unspecified residents of Eight Mile, Alabama, on the basis of race in violation of the Fair Housing Act by failing to adequately address the odorant release that occurred in 2008. The Company believes there is no basis for the complaint, HUD has no jurisdiction in the matter, and there will be no material impact on its future financial condition or results of operations.

INTERIM FINANCIAL INFORMATION (

INTERIM FINANCIAL INFORMATION (UNAUDITED)	12 Months Ended
	Sep. 30, 2018
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 2018 and 2017 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 2018 Total Operating Revenues $ 561.8 $ 813.4 $ 350.6 $ 239.2 Operating Income (Loss) 105.1 141.8 52.4 (19.6 ) Net Income (Loss) 116.0 98.2 25.9 (25.9 ) Basic Earnings (Loss) Per Share of Common Stock $ 2.40 $ 2.03 $ 0.52 $ (0.51 ) Diluted Earnings (Loss) Per Share of Common Stock $ 2.39 $ 2.03 $ 0.52 $ (0.51 ) 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 ) Spire Missouri In the opinion of Spire Missouri, the quarterly information presented below for fiscal years 2018 and 2017 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 2018 Total Operating Revenues $ 392.3 $ 533.2 $ 215.5 $ 144.6 Operating Income (Loss) 74.8 52.1 21.0 (6.6 ) Net Income (Loss) 89.4 38.4 11.5 (10.0 ) 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 Spire Alabama In the opinion of Spire Alabama, the quarterly information presented below for fiscal years 2018 and 2017 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 2018 Total Operating Revenues $ 120.8 $ 218.3 $ 100.3 $ 61.3 Operating Income (Loss) 19.0 78.2 12.3 (10.9 ) Net Income (Loss) (49.6 ) 55.6 6.3 (11.0 ) 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 )

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Sep. 30, 2018
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, Spire Alabama and the subsidiaries of Spire EnergySouth Inc. (“Spire EnergySouth”) are collectively referred to as “the Utilities.” The subsidiaries of Spire EnergySouth are Spire Gulf Inc. and Spire Mississippi Inc. 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 include the accounts of the Company and all its subsidiaries. One subsidiary acquired an 80% voting interest in a natural gas storage facility in December 2017, and the redeemable noncontrolling interest is shown as temporary equity on the balance sheet. Transactions and balances between consolidated entities have been eliminated from the consolidated financial statements of Spire. 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.
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”).
PROPERTY, PLANT, AND EQUIPMENT	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 2018 , 2017 and 2016 , 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 in fiscal years 2018 , 2017 and 2016 was 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.
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 14 , Regulatory Matters.
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, 2018 and September 30, 2017 was less than the LIFO cost by $14.5 and $20.8 , respectively. The carrying value of the Utilities’ inventory is not adjusted to the lower of net realizable value or market prices because, pursuant to Purchased Gas Adjustment (“PGA”) clauses or a Gas Supply Adjustment (“GSA”) rider, 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 – Spire’s acquisitions, including the recent transactions described below, were accounted for 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, 2018, 2017 and 2016, 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, 2018 and 2017 were $29.7 and $30.1 , 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 amount of accrued unbilled revenues for Spire Alabama was $1.9 at both September 30, 2018 and 2017 . 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 their business, certain subsidiaries of the Company enter 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 9 , 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 realized or settled. The effects on deferred tax assets and liabilities of a change in enacted tax rates is recognized in income or loss for non-regulated operations, and in a regulatory asset or regulatory liability for regulated operations. 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. For additional information on the accounting for income taxes, refer to Note 11 , Income Taxes.
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	CASH, CASH EQUIVALENTS, AND RESTRICTED CASH – 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	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. 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	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: 2018 2017 2016 Spire $ 98.2 $ 84.6 $ 75.5 Spire Missouri 68.9 60.7 57.4 Spire Alabama 25.4 19.5 17.9 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. Spire Missouri and Spire Alabama borrowed funds from the Company and incurred related interest, as reflected in their separate financial statements, and they participated in normal intercompany shared services transactions.
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 accounts for share-based compensation arrangements in accordance with ASC Topic 718, Compensation - Stock 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, forfeitures are recognized in the period they occur. Prior to fiscal 2017, 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 PRONOUNCEMENTS	NEW ACCOUNTING PRONOUNCEMENTS – In November 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-18, Statement of Cash Flows: Restricted Cash . This guidance requires the statement of cash flows to present changes in the total of cash, cash equivalents and restricted cash. Prior to the adoption of this ASU, the relevant accounting guidance did not require the statement of cash flows to include changes in restricted cash. The Company, Spire Missouri and Spire Alabama adopted the standard retrospectively in 2018 with no impact to 2017 or 2016. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . This guidance permits companies to make an election to reclassify stranded income tax effects from the recently enacted Tax Cuts and Jobs Act included in accumulated other comprehensive income or loss (“AOCI”) to retained earnings. ASU 2018-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company, Spire Missouri and Spire Alabama elected to early adopt this guidance in the quarter ended September 30, 2018. The reclassifications from the adoption of this standard are shown on the statements of shareholders’ equity of the Company and Spire Missouri. There was no effect for Spire Alabama. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers . Under the new standard, an entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under previous guidance. ASU No. 2014-09 also requires disclosures that will enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Existing alternative revenue program guidance, though excluded by the FASB in updating specific guidance associated with revenue from contracts with customers, was relocated without substantial modification to accounting guidance for rate-regulated entities. It will require separate presentation of such revenues in the statement of income. Entities have the option of using either a full retrospective or modified retrospective approach in adopting this guidance. In August 2015, the FASB issued ASU No. 2015-14, which made the guidance in ASU No. 2014-09 effective for fiscal years beginning after December 15, 2017, and interim periods within those years. In 2016 and 2017, the FASB issued related ASU Nos. 2016-08, 2016-10, 2016-11, 2016-12, 2016-20, and 2017-14, which further modified the standards for accounting for revenue. The Company, Spire Missouri and Spire Alabama have completed their evaluation of their sources of revenue and related contracts and plan to adopt the new guidance in the first quarter of fiscal 2019 using the modified retrospective approach with no material effect on their financial position, results of operations, or cash flows. In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard requires lessees to recognize a right-of-use asset and lease liability for almost all lease contracts based on the present value of lease payments. There is an exemption for short-term leases. The ASU provides new guidelines for identifying and classifying a lease, and classification affects the pattern and income statement line item for the related expense. ASU Nos. 2018-01, 2018-10, and 2018-11, issued in January and July of 2018, amended several aspects of the new lease guidance, including providing an additional practical expedient, an additional transition method, and clarification of the related transition and accounting for land easements. The updates may be applied using a modified retrospective transition approach for leases existing at, or entered into after, the beginning of (1) the earliest comparative period presented in the financial statements or (2) the period of adoption. The ASUs are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company, Spire Missouri and Spire Alabama are currently assessing the impacts of adopting these standards in the first quarter of fiscal 2020. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments . The standard introduces new guidance for the accounting for credit losses on instruments within its scope, including trade receivables. It is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and may be adopted a year earlier. The new guidance will be initially applied through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The Company, Spire Missouri and Spire Alabama are currently assessing the timing and impacts of adopting this standard, which must be adopted by the first quarter of fiscal 2021. In March 2017, the FASB issued ASU No. 2017-07, Compensation – Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The amended guidance requires that the service cost component of pension and postretirement benefit costs be presented within the same line item in the income statement as other compensation costs (except for the amount being capitalized), while other components are to be presented outside the subtotal of operating income and are no longer eligible for capitalization. The ASU is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. The amended guidance will be applied retrospectively for income statement presentation and prospectively for capitalization. The Company, Spire Missouri and Spire Alabama will adopt this standard in the first quarter of fiscal 2019 using a practical expedient permitting the use of the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements. They will continue to capitalize the non-service cost components as allowed for regulatory reporting, but those capitalized amounts will be reported as regulatory assets rather than plant. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities . The amendments in this ASU more closely align the results of hedge accounting with risk management activities through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results in the financial statements. They are effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, and early application is permitted. The Company, Spire Missouri and Spire Alabama are currently assessing the effects of this new guidance, as well as the timing of adoption. In August 2018, the FASB issued ASU No. 2018-15, Intangibles – Goodwill and Other – Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . Previous GAAP did not specifically address the accounting for implementation costs of a hosting arrangement that is a service contract. The amendments in this update clarify that accounting and align the accounting for implementation costs for hosting arrangements, regardless of whether they convey a license to the hosted software. The amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period. The amendments in this ASU may be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company, Spire Missouri and Spire Alabama are still assessing the effects of this new guidance but currently expect early adoption.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Schedule of capital expenditures 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 until paid. September 30 2018 2017 2016 Spire $ 62.1 $ 41.0 $ 30.4 Spire Missouri 36.7 28.9 14.8 Spire Alabama 8.9 9.4 6.8
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 2018 2017 2018 2017 2018 2017 Asset retirement obligations, beginning of year $ 296.6 $ 206.4 $ 158.6 $ 75.2 $ 128.4 $ 120.1 Liabilities incurred during the period 5.5 5.5 0.6 0.3 3.5 5.2 Liabilities settled during the period (11.2 ) (4.6 ) (8.9 ) (1.1 ) (1.8 ) (1.9 ) Accretion 12.7 9.1 6.6 3.6 5.6 5.0 Revisions in estimated cash flows 16.9 80.2 17.2 80.6 — — Business combinations 0.6 — — — — — Asset retirement obligations, end of year $ 321.1 $ 296.6 $ 174.1 $ 158.6 $ 135.7 $ 128.4
Schedule of Pro Forma Information	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. 2018 2017 2016 Total Operating Revenues $ 102.1 $ 95.5 $ 3.3 Net Income (Loss) 13.8 9.4 (0.2 ) 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 2016. 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. 2018 2017 2016 Total Operating Revenues $ 1,965.0 $ 1,740.7 $ 1,632.4 Net Income 214.2 161.6 153.9 Basic Earnings Per Share $ 4.35 $ 3.44 $ 3.48 Diluted Earnings Per Share 4.33 3.43 3.46
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, 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 Balance as of September 30, 2018 $ 210.2 $ — $ 961.4 $ 1,171.6
Schedule of gross receipts taxes	The following table presents gross receipts taxes recorded as revenues: 2018 2017 2016 Spire $ 98.2 $ 84.6 $ 75.5 Spire Missouri 68.9 60.7 57.4 Spire Alabama 25.4 19.5 17.9
Schedule of inter-company transactions	In addition, Spire Missouri’s other transactions with affiliates included: 2018 2017 2016 Purchases of natural gas from Spire Marketing $ 71.5 $ 74.4 $ 46.3 Sales of natural gas to Spire Marketing 0.3 7.8 1.9 Transportation services received from Spire NGL Inc. 1.0 1.0 1.0
Schedule of allowance for doubtful accounts	Spire Spire Missouri Spire Alabama 2018 2017 2016 2018 2017 2016 2018 2017 2016 Allowance at beginning of year $ 18.3 $ 20.5 $ 14.2 $ 14.1 $ 16.1 $ 10.0 $ 2.6 $ 3.3 $ 4.2 Additions charged to expense 14.6 10.6 6.5 11.9 10.1 6.2 2.1 0.2 0.6 Net deductions (10.5 ) (12.8 ) (0.2 ) (10.0 ) (12.1 ) (0.1 ) (0.8 ) (0.9 ) (1.5 ) Allowance at end of year $ 22.4 $ 18.3 $ 20.5 $ 16.0 $ 14.1 $ 16.1 $ 3.9 $ 2.6 $ 3.3

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Restricted stock and restricted stock unit activity	Fiscal 2018 activity of restricted stock units subject to performance and/or market conditions is presented below: Units Weighted Average Grant Date Fair Value Per Unit Nonvested at September 30, 2017 282,015 $ 56.32 Granted 87,960 $ 79.88 Vested (81,933 ) $ 47.80 Forfeited (21,960 ) $ 56.73 Nonvested at September 30, 2018 266,082 $ 66.69 Time-vested restricted stock and stock unit activity for fiscal 2018 is presented below: Shares/ Units Weighted Average Grant Date Fair Value Per Share Nonvested at September 30, 2017 110,940 $ 55.85 Granted 47,780 $ 73.85 Vested (47,928 ) $ 53.48 Forfeited (7,192 ) $ 65.25 Nonvested at September 30, 2018 103,600 $ 64.60
Significant assumptions used in the Monte Carlo simulations	The significant assumptions used in the Monte Carlo simulations are as follows: 2018 2017 2016 Risk-free interest rate 1.76% 1.39% 1.14% Expected dividend yield of stock — — — Expected volatility of stock 16.0% 16.3% 15.0% Vesting period 2.9 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: 2018 2017 2016 Total compensation cost $ 6.9 $ 7.4 $ 6.7 Compensation cost capitalized (1.3 ) (3.3 ) (2.2 ) Prior period disallowed stock compensation capitalization $ 6.9 $ — $ — Compensation cost recognized in net income 12.5 4.1 4.5 Income tax benefit recognized in net income (4.0 ) (1.5 ) (1.7 ) Compensation cost recognized in net income, net of income tax $ 8.5 $ 2.6 $ 2.8

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	12 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	2018 2017 2016 Basic Earnings Per Share: Net Income $ 214.2 $ 161.6 $ 144.2 Less: Income allocated to participating securities 0.5 0.4 0.5 Net Income Available to Common Shareholders $ 213.7 $ 161.2 $ 143.7 Weighted Average Shares Outstanding (in millions) 49.1 46.9 44.1 Basic Earnings Per Share of Common Stock $ 4.35 $ 3.44 $ 3.26 Diluted Earnings per Share: Net Income $ 214.2 $ 161.6 $ 144.2 Less: Income allocated to participating securities 0.5 0.4 0.5 Net Income Available to Common Shareholders $ 213.7 $ 161.2 $ 143.7 Weighted Average Shares Outstanding (in millions) 49.1 46.9 44.1 Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* 0.2 0.1 0.2 Weighted Average Diluted Shares (in millions) 49.3 47.0 44.3 Diluted Earnings Per Share of Common Stock $ 4.33 $ 3.43 $ 3.24 * Calculation excludes certain outstanding shares (shown in millions by period at the right) attributable to stock units subject to performance or market conditions and restricted stock, which could have a dilutive effect in the future 0.4 0.5 0.3

SHAREHOLDERS' EQUITY (Tables)

SHAREHOLDERS' EQUITY (Tables)	12 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Schedule of accumulated other comprehensive income (loss)	The components of AOCI, 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 Debt Securities Total Spire 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 Other comprehensive income 2.0 0.3 0.2 2.5 Reclassification of certain income tax effects 1.0 (0.3 ) — 0.7 Balance at September 30, 2018 $ 7.9 $ (1.5 ) $ — $ 6.4 Spire Missouri 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 ) Other comprehensive (loss) income (0.1 ) 0.3 0.2 0.4 Reclassification of certain income tax effects — (0.3 ) — (0.3 ) Balance at September 30, 2018 $ — $ (1.6 ) $ — $ (1.6 )

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
	Sep. 30, 2018
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 after September 30, 2018 are as follows: 2019 2020 2021 2022 2023 Spire $ 175.5 $ 43.2 $ 57.0 $ 52.0 $ 332.3 Spire Missouri 50.0 — — — 305.0 Spire Alabama — 40.0 — 50.0 —

NOTES PAYABLE AND CREDIT AGRE_2

NOTES PAYABLE AND CREDIT AGREEMENTS (Tables)	12 Months Ended
	Sep. 30, 2018
Short-term Debt [Line Items]
Short-term borrowings	Information about Spire’s consolidated short-term borrowings is presented in the following table. Commercial Paper Borrowings Revolving Credit Facility Borrowings Total Short ‑t erm Borrowings Year Ended September 30, 2018 Weighted average borrowings outstanding $408.5 $0.1 $408.6 Weighted average interest rate 2.0% 2.8% 2.0% Range of borrowings outstanding $146.0 - $632.9 $0.0 - $25.0 $146.0 - $632.9 As of September 30, 2018 Borrowings outstanding $553.6 $— $553.6 Weighted average interest rate 2.4% —% 2.4% As of September 30, 2017 Borrowings outstanding $477.3 $— $477.3 Weighted average interest rate 1.5% —% 1.5% From the total short-term borrowings as of September 30, 2018, Spire used $540.5 to provide funding to the Utilities and Spire Storage. Information about Spire Missouri’s and Spire Alabama’s borrowings from Spire is presented in the following table. Spire Missouri Spire Alabama Year Ended September 30, 2018 Weighted average borrowings outstanding $210.5 $103.9 Weighted average interest rate 2.1% 2.0% Range of borrowings outstanding $101.5 - $345.3 $33.6 - $188.6 As of September 30, 2018 Borrowings outstanding $345.3 $142.5 Weighted average interest rate 2.3% 2.3% As of September 30, 2017 Borrowings outstanding $203.0 $169.9 Weighted average interest rate 1.5% 1.5%

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Sep. 30, 2018
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 were as follows: Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Spire As of September 30, 2018 Cash and cash equivalents $ 4.4 $ 4.4 $ 4.4 $ — Short-term debt 553.6 553.6 — 553.6 Long-term debt, including current portion 2,075.6 2,074.0 — 2,074.0 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
Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments	Spire Missouri As of September 30, 2018 Cash and cash equivalents $ 2.0 $ 2.0 $ 2.0 $ — Short-term debt 345.3 345.3 — 345.3 Long-term debt, including current portion 874.4 906.6 — 906.6 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
Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments	Spire Alabama As of September 30, 2018 Short-term debt $ 142.5 $ 142.5 $ — $ 142.5 Long-term debt 322.6 321.7 — 321.7 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

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Sep. 30, 2018
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, 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, 2018 or 2017 . 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 “Other Property and 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 9 , 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, 2018 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 20.3 $ — $ — $ — $ 20.3 NYMEX/ICE natural gas contracts 2.7 — — (2.7 ) — Gas Marketing: NYMEX/ICE natural gas contracts 0.2 4.0 — (4.2 ) — Natural gas commodity contracts — 17.5 — (1.5 ) 16.0 Other: U.S. stock/bond mutual funds 8.9 — — — 8.9 Interest rate swaps — 3.0 — — 3.0 Total $ 32.1 $ 24.5 $ — $ (8.4 ) $ 48.2 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 0.9 10.5 — (11.4 ) — Natural gas commodity contracts — 7.5 0.2 (1.5 ) 6.2 Total $ 2.8 $ 18.0 $ 0.2 $ (14.8 ) $ 6.2 As of September 30, 2017 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — NYMEX 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
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, 2018 ASSETS U.S. stock/bond mutual funds $ 20.3 $ — $ — $ — $ 20.3 NYMEX/ICE natural gas contracts 2.7 — — (2.7 ) — Total $ 23.0 $ — $ — $ (2.7 ) $ 20.3 LIABILITIES NYMEX/ICE natural gas contracts $ 1.9 $ — $ — $ (1.9 ) $ — As of September 30, 2017 ASSETS U.S. stock/bond mutual funds $ 18.3 $ 4.1 $ — $ — $ 22.4 NYMEX/ICE natural gas contracts 3.4 — — (3.4 ) — NYMEX 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 ) $ —

DERIVATIVE INSTRUMENTS AND HE_2

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)	12 Months Ended
	Sep. 30, 2018
Derivative [Line Items]
Derivative instruments and hedging activities	Open NYMEX and ICE natural gas futures and swap positions at September 30, 2018 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 2019 — $ — 7.87 $ 3.04 Fiscal 2020 — — 2.00 2.93 Fiscal 2021 — — 0.14 2.94 NYMEX/ICE open long futures/swap positions Fiscal 2019 24.12 2.80 9.27 2.89 Fiscal 2020 2.68 2.69 2.11 2.85 Fiscal 2021 — — 0.55 2.87 Fiscal 2022 — — 0.25 2.98 Fiscal 2023 — — 0.01 2.86 ICE open short daily swap positions Fiscal 2019 — — 2.54 2.95 ICE open long daily swap positions Fiscal 2019 — — 0.57 2.92 ICE open short basis swap positions Fiscal 2019 — — 52.48 0.23 Fiscal 2020 — — 3.80 0.25 ICE open long basis swap positions Fiscal 2019 — — 49.99 0.64 Fiscal 2020 — — 3.18 0.68 Fiscal 2022 — — 0.92 0.52 Fiscal 2023 — — 0.16 0.52
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 Comprehensive Income Location of Gain (Loss) Recorded in Income 2018 2017 2016 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gas Marketing natural gas contracts $ — $ — $ (0.6 ) Gas Utility gasoline and heating oil contracts — 0.1 — Interest rate swaps 3.9 11.4 (3.4 ) Total $ 3.9 $ 11.5 $ (4.0 ) Effective portion of gain (loss) reclassified from AOCI to income: Natural gas contracts Gas Marketing Operating Revenues $ — $ (0.4 ) $ 4.3 Gas Marketing Operating Expenses — 0.1 (4.9 ) Subtotal — (0.3 ) (0.6 ) Gasoline and heating oil contracts Gas Utility Other Operating Expenses 0.1 0.2 (0.5 ) Interest rate swaps Interest Expense 1.4 0.1 — Total $ 1.5 $ — $ (1.1 ) 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 Subtotal — — 0.2 Gasoline and heating oil contracts Gas Utility Other Operating Expenses — — 0.1 Interest rate swaps Interest Expense — 0.5 — Total $ — $ 0.5 $ 0.3 Derivatives Not Designated as Hedging Instruments* Gain (loss) recognized in income on derivatives: Natural gas commodity contracts Gas Marketing Operating Revenues $ 10.2 $ 0.7 $ 12.3 Gas Marketing Operating Expenses (8.1 ) — — NYMEX / ICE natural gas contracts Gas Marketing Operating Revenues — (4.4 ) (1.7 ) Total $ 2.1 $ (3.7 ) $ 10.6 * 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, 2018 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Other: Interest rate swaps Derivative Instrument Assets 3.0 Derivative Instrument Assets — Subtotal 3.0 — Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Accounts Receivable – Other 2.7 Accounts Receivable – Other 1.9 Gas Marketing: NYMEX / ICE natural gas contracts Derivative Instrument Assets 3.8 Derivative Instrument Assets 10.7 Deferred Charges – Other 0.4 Deferred Charges – Other 0.7 Natural gas commodity Derivative Instrument Assets 10.9 Derivative Instrument Assets 1.0 Deferred Charges – Other 6.3 Deferred Charges – Other 0.2 Current Liabilities – Other 0.3 Current Liabilities – Other 6.3 Deferred Credits – Other — Deferred Credits – Other 0.2 Subtotal 24.4 21.0 Total derivatives $ 27.4 $ 21.0 September 30, 2017 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 Derivative Instrument Assets — Derivative Instrument Assets 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 Deferred Charges – Other 0.4 Deferred Charges – Other — 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 * 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 8 , 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: 2018 2017 Fair value of asset derivatives presented above $ 27.4 $ 13.0 Fair value of cash margin (payable) receivable offset with derivatives 6.4 (1.5 ) Netting of assets and liabilities with the same counterparty (14.8 ) (5.3 ) Total $ 19.0 $ 6.2 Derivative Instrument Assets, per Consolidated Balance Sheets: Derivative instrument assets $ 13.3 $ 5.9 Deferred Charges – Other 5.7 0.3 Total $ 19.0 $ 6.2 Fair value of liability derivatives presented above $ 21.0 $ 13.3 Netting of assets and liabilities with the same counterparty (14.8 ) (5.3 ) Total $ 6.2 $ 8.0 Derivative Instrument Liabilities, per Consolidated Balance Sheets: Current Liabilities – Other $ 6.0 $ 4.9 Deferred Credits – Other 0.2 3.1 Total $ 6.2 $ 8.0
Spire Missouri
Derivative [Line Items]
Derivative instruments and hedging activities	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, 2018 were as follows: MMBtu (millions) Avg. Price Per MMBtu NYMEX/ICE open long futures/swap positions Fiscal 2019 24.12 $ 2.80 Fiscal 2020 2.68 2.69
Effect of derivative instruments on the Statements of Consolidated Income and Statements of Consolidated Comprehensive Income	Effect of Derivative Instruments on the Statements of Comprehensive Income Location of Gain (Loss) Recorded in Income 2018 2017 2016 Derivatives in Cash Flow Hedging Relationships Effective portion of gain (loss) recognized in OCI on derivatives: Gasoline and heating oil contracts $ — $ 0.1 $ — Effective portion of gain (loss) reclassified from AOCI to income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ 0.1 $ 0.2 $ (0.5 ) Ineffective portion of gain (loss) on derivatives recognized in income: Gasoline and heating oil contracts Gas Utility Other Operating Expenses $ — $ — $ 0.1 * 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 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, 2018 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives not designated as hedging instruments Natural gas contracts Accounts Receivable – Other 2.7 Accounts Receivable – Other 1.9 Total derivatives $ 2.7 $ 1.9 September 30, 2017 Derivatives designated as hedging instruments Gasoline and heating oil contracts Derivative Instrument Assets $ 0.1 Derivative Instrument Assets $ — Subtotal 0.1 — 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 * 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 8 , 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: 2018 2017 Fair value of asset derivatives presented above $ 2.7 $ 3.5 Fair value of cash margin (payable) receivable offset with derivatives (0.8 ) (1.5 ) Netting of assets and liabilities with the same counterparty (1.9 ) (1.9 ) Total $ — $ 0.1 Derivative Instrument Assets, per Balance Sheets: Derivative instrument assets $ — $ 0.1 Total $ — $ 0.1 Fair value of liability derivatives presented above $ 1.9 $ 1.9 Netting of assets and liabilities with the same counterparty (1.9 ) (1.9 ) Total $ — $ —

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Sep. 30, 2018
Income Tax Contingency [Line Items]
Net provision for income tax	The Company’s provision (benefit) for income taxes during the fiscal years ended September 30, 2018 , 2017 , and 2016 was as follows: 2018 2017 2016 Federal Current $ — $ 0.1 $ 0.1 Deferred (22.7 ) 67.7 62.0 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current 2.2 0.5 0.6 Deferred (5.8 ) 9.5 7.0 Total income tax (benefit) expense $ (26.5 ) $ 77.6 $ 69.5
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: 2018 2017 2016 Federal income tax statutory rate 24.5 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 3.4 2.8 2.8 Certain expenses capitalized on books and deducted on tax return (2.3 ) (2.3 ) (3.4 ) Taxes related to prior years (0.4 ) (0.9 ) (0.2 ) Tax law changes (35.9 ) — — Amortization of excess deferred taxes (1.8 ) — — Other items – net * (1.6 ) (2.2 ) (1.7 ) Effective income tax rate (14.1 )% 32.4 % 32.5 % * 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 were as follows: 2018 2017 Deferred tax assets: Reserves not currently deductible $ 25.9 $ 31.5 Pension and other postretirement benefits 75.6 58.6 Operating losses 162.7 169.6 Regulatory amount due to customers, net 41.8 — Other 8.2 26.0 Deferred tax assets 314.2 285.7 Less: valuation allowance 1.4 0.5 Total deferred tax assets 312.8 285.2 Deferred tax liabilities: Relating to property 518.3 728.3 Regulatory pension and other postretirement benefits 117.1 108.0 Deferred gas costs 2.3 30.6 Other** 110.9 125.8 Total deferred tax liabilities 748.6 992.7 Net deferred tax liability $ 435.8 $ 707.5 ** Other consists primarily of Goodwill related liabilities. The total amounts recorded, before reduction for amounts returned to customers, for the year ended September 30, 2018, are presented in the table below. Adjustment to deferred tax liabilities $ (318.3 ) Adjustment to deferred income tax expense (75.0 ) Adjustment to regulatory assets (75.9 ) Adjustment to regulatory liabilities 167.4
Unrecognized Tax Benefit Reconciliation	The following table presents a reconciliation of the beginning and ending balances of the Company’s unrecognized tax benefits: 2018 2017 2016 Unrecognized tax benefits, beginning of year $ 11.0 $ 10.0 $ 7.1 Decrease related to tax law changes (4.0 ) — — Increases related to tax positions taken in current year 1.2 2.4 3.4 Reductions due to lapse of applicable statute of limitations (0.1 ) (1.4 ) (0.5 ) Unrecognized tax benefits, end of year $ 8.1 $ 11.0 $ 10.0
Spire Missouri
Income Tax Contingency [Line Items]
Net provision for income tax	Spire Missouri’s provision (benefit) for income taxes during the fiscal years ended September 30, 2018 , 2017 , and 2016 was as follows: 2018 2017 2016 Federal Current $ — $ — $ — Deferred (26.1 ) 42.0 37.5 Investment tax credits (0.2 ) (0.2 ) (0.2 ) State and local Current — — 0.1 Deferred (6.3 ) 5.7 8.0 Total income tax (benefit) expense $ (32.6 ) $ 47.5 $ 45.4
Effective income tax rate variation from stated tax rate	Spire Missouri’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2018 2017 2016 Federal income tax statutory rate 24.5 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 3.4 2.8 2.8 Certain expenses capitalized on books and deducted on tax return (4.6 ) (3.5 ) (4.8 ) Taxes related to prior years (0.7 ) (1.4 ) (0.2 ) Tax law changes (50.3 ) — — Amortization of excess deferred taxes (3.6 ) — — Other items – net * (2.5 ) (3.3 ) (2.8 ) Effective income tax rate (33.8 )% 29.6 % 30.0 % * Other consists primarily of property adjustments.
Significant items in net deferred tax liability	Spire Missouri’s significant items comprising the net deferred tax liability reported in the Balance Sheets as of September 30 were as follows: 2018 2017 Deferred tax assets: Reserves not currently deductible $ 20.0 $ 25.3 Pension and other postretirement benefits 71.9 52.7 Deferred gas costs 0.5 — Operating losses 65.2 52.0 Regulatory amount due to customers 38.0 — Deferred tax assets 195.6 130.0 Less: valuation allowance 1.4 0.5 Total deferred tax assets 194.2 129.5 Deferred tax liabilities: Relating to utility property 372.6 563.2 Regulatory pension and other postretirement benefits 113.4 108.0 Deferred gas costs — 25.0 Other 69.2 57.1 Total deferred tax liabilities 555.2 753.3 Net deferred tax liability $ 361.0 $ 623.8 The total amounts recorded, before reduction for amounts returned to customers, for the year ended September 30, 2018, are presented in the table below. Adjustment to deferred tax liabilities $ (285.3 ) Adjustment to deferred income tax expense (57.0 ) Adjustment to regulatory assets (78.1 ) Adjustment to regulatory liabilities 150.2
Unrecognized Tax Benefit Reconciliation	The following table presents a reconciliation of the beginning and ending balances of Spire Missouri unrecognized tax benefits: 2018 2017 2016 Unrecognized tax benefits, beginning of year $ 10.7 $ 9.7 $ 6.9 Decrease related to tax law changes (4.0 ) — — Increases related to tax positions taken in current year 1.1 2.4 3.3 Reductions due to lapse of applicable statute of limitations — (1.4 ) (0.5 ) Unrecognized tax benefits, end of year $ 7.8 $ 10.7 $ 9.7
Spire Alabama
Income Tax Contingency [Line Items]
Net provision for income tax	Spire Alabama’s provision for income taxes charged during the fiscal years ended September 30, 2018 , 2017 , and 2016 , was as follows: 2018 2017 2016 Federal Current $ — $ — $ (0.8 ) Deferred 81.5 31.6 29.4 State and local Current — — — Deferred 0.1 4.2 3.8 Total income tax expense $ 81.6 $ 35.8 $ 32.4
Effective income tax rate variation from stated tax rate	Spire Alabama’s effective income tax rate varied from the federal statutory income tax rate for each year due to the following: 2018 2017 2016 Federal income tax statutory rate 24.5 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefits 3.8 2.8 2.8 Tax law change 70.0 — — Other items – net 0.1 0.3 0.1 Effective income tax rate 98.4 % 38.1 % 37.9 %
Significant items in net deferred tax liability	The total amounts recorded, before reduction for amounts returned to customers, for the year ended September 30, 2018, are presented in the table below. Adjustment to deferred tax assets $ (61.0 ) Adjustment to deferred income tax expense 58.8 Adjustment to regulatory assets 2.2 Spire Alabama’s significant items comprising the net deferred tax asset reported in the Balance Sheets as of September 30 were as follows: 2018 2017 Deferred tax assets: Reserves not currently deductible $ 5.3 $ 6.0 Pension and other postretirement benefits — 4.4 Goodwill 129.6 214.4 Operating losses 86.0 88.3 Total deferred tax assets 220.9 313.1 Deferred tax liabilities: Relating to utility property 111.9 119.3 Pension and other postretirement benefits 1.8 — Other 5.4 8.2 Total deferred tax liabilities 119.1 127.5 Net deferred tax asset $ 101.8 $ 185.6

PENSION PLANS AND OTHER POSTR_2

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Tables)	12 Months Ended
	Sep. 30, 2018
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, 2018 Cash and cash equivalents $ 50.6 $ — $ — $ 50.6 Equity mutual funds - U.S. 42.7 21.2 — 63.9 Equity mutual funds - international 20.7 4.1 — 24.8 Debt securities: U.S. bond mutual funds 35.8 64.9 — 100.7 U.S. government 31.7 5.6 — 37.3 U.S. corporate 152.1 — — 152.1 U.S. municipal 3.6 3.0 — 6.6 International 43.9 7.0 — 50.9 Derivatives and margin (payable) (0.8 ) — — (0.8 ) 103-12 Direct Filing Entities — 13.1 — 13.1 Total $ 380.3 $ 118.9 $ — $ 499.2 As of September 30, 2017 Cash and cash equivalents $ 37.3 $ — $ — $ 37.3 Equity mutual funds - U.S. 42.1 25.4 — 67.5 Equity mutual funds - international 37.4 11.2 — 48.6 Debt securities: U.S. bond mutual funds 34.4 68.5 — 102.9 U.S. government 33.2 4.5 — 37.7 U.S. corporate 183.7 — — 183.7 U.S. 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 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, 2018 Cash and cash equivalents $ 3.7 $ — $ — $ 3.7 U.S. stock/bond mutual funds 190.2 74.5 — 264.7 International fund — 15.1 — 15.1 Total $ 193.9 $ 89.6 $ — $ 283.5 As of September 30, 2017 Cash and cash equivalents $ 4.0 $ — $ — $ 4.0 U.S. 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
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 2018 2017 2016 2018 2017 2016 2018 2017 2016 Service cost – benefits earned during the period $ 20.2 $ 20.5 $ 15.3 $ 12.7 $ 12.7 $ 10.0 $ 6.4 $ 6.2 $ 5.3 Interest cost on projected benefit obligation 27.4 27.9 28.0 19.5 19.5 21.7 5.5 6.1 6.3 Expected return on plan assets (37.0 ) (38.5 ) (34.9 ) (27.2 ) (28.1 ) (26.7 ) (6.5 ) (7.2 ) (8.2 ) Amortization of prior service cost (credit) (0.9 ) 1.0 0.4 0.9 1.0 0.4 (1.8 ) — — Amortization of actuarial loss 10.9 12.5 8.0 9.4 10.7 7.9 1.5 1.8 0.1 Loss on lump-sum settlements and curtailments 18.6 17.9 3.3 16.1 13.5 — 2.4 4.6 3.3 Special termination benefits — 0.9 1.6 — — 1.6 — — — Subtotal 39.2 42.2 21.7 31.4 29.3 14.9 7.5 11.5 6.8 Regulatory adjustment 37.4 (2.4 ) 17.8 32.1 (4.1 ) 11.7 4.5 1.8 6.1 Net pension cost $ 76.6 $ 39.8 $ 39.5 $ 63.5 $ 25.2 $ 26.6 $ 12.0 $ 13.3 $ 12.9
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 2018 2017 2016 2018 2017 2016 2018 2017 2016 Current year actuarial (gain) loss $ (1.4 ) $ 14.1 $ 46.8 $ 2.2 $ 14.8 $ 21.6 $ (0.6 ) $ 3.3 $ 25.2 Amortization of actuarial loss (10.9 ) (12.5 ) (8.0 ) (9.4 ) (10.7 ) (7.9 ) (1.5 ) (1.8 ) (0.1 ) Acceleration of loss recognized due to settlement (18.5 ) (18.2 ) (3.3 ) (16.1 ) (13.5 ) — (2.4 ) (4.5 ) (3.3 ) Current year service (credit) cost (0.1 ) — 5.0 — — 5.0 — — — Current year prior year service cost — (20.7 ) — — — — — (20.7 ) — Transfer due to merger 0.1 — — 0.1 — — — — — Amortization of prior service cost (2.9 ) (1.0 ) (0.4 ) (0.9 ) (1.0 ) (0.4 ) — — — Amortization of transition asset 1.8 — — — — — 1.8 — — Subtotal (31.9 ) (38.3 ) 40.1 (24.1 ) (10.4 ) 18.3 (2.7 ) (23.7 ) 21.8 Regulatory adjustment 31.6 38.0 (39.8 ) 23.8 10.1 (18.0 ) 2.7 23.7 (21.8 ) Total recognized in OCI $ (0.3 ) $ (0.3 ) $ 0.3 $ (0.3 ) $ (0.3 ) $ 0.3 $ — $ — $ —
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 2018 2017 2018 2017 2018 2017 Benefit obligation, beginning of year $ 748.8 $ 794.7 $ 539.6 $ 560.0 $ 148.2 $ 174.3 Service cost 20.2 20.5 12.7 12.7 6.4 6.2 Interest cost 27.4 27.9 19.5 19.5 5.5 6.1 Actuarial (gain) loss (34.9 ) (0.9 ) (26.0 ) (0.5 ) (3.8 ) 1.6 Plan amendments (2.0 ) (20.7 ) — — — (20.7 ) Plan mergers — — (0.3 ) — — — Settlement loss 7.6 14.6 7.6 12.2 — 2.4 Special termination benefits — 0.9 — — — — Settlement benefits paid (82.8 ) (62.2 ) (65.5 ) (43.5 ) (17.3 ) (18.7 ) Regular benefits paid (19.7 ) (26.0 ) (14.3 ) (20.8 ) (2.7 ) (3.0 ) Benefit obligation, end of year $ 664.6 $ 748.8 $ 473.3 $ 539.6 $ 136.3 $ 148.2 Accumulated benefit obligation, end of year $ 636.0 $ 701.4 $ 446.5 $ 500.4 $ 134.5 $ 142.8
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 2018 2017 2018 2017 2018 2017 Fair value of plan assets, beginning of year $ 531.6 $ 540.5 $ 385.9 $ 395.7 $ 97.9 $ 100.0 Actual return on plan assets 11.2 38.0 6.4 25.1 3.3 7.7 Employer contributions 58.9 41.3 36.9 29.4 20.1 11.9 Divestitures — — (0.3 ) — — — Settlement benefits paid (82.8 ) (62.2 ) (65.5 ) (43.5 ) (17.3 ) (18.7 ) Regular benefits paid (19.7 ) (26.0 ) (14.3 ) (20.8 ) (2.7 ) (3.0 ) Fair value of plan assets, end of year $ 499.2 $ 531.6 $ 349.1 $ 385.9 $ 101.3 $ 97.9 Funded status of plans, end of year $ (165.4 ) $ (217.2 ) $ (124.2 ) $ (153.7 ) $ (35.0 ) $ (50.3 )
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 2018 2017 2018 2017 2018 2017 Current liabilities $ (0.6 ) $ (0.5 ) $ (0.6 ) $ (0.5 ) $ — $ — Noncurrent liabilities (164.8 ) (216.7 ) (123.6 ) (153.2 ) (35.0 ) (50.3 ) Total $ (165.4 ) $ (217.2 ) $ (124.2 ) $ (153.7 ) $ (35.0 ) $ (50.3 ) 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 2018 2017 2018 2017 2018 2017 Net actuarial loss $ 132.1 $ 163.0 $ 102.8 $ 126.2 $ 36.4 $ 40.9 Prior service (credit) cost (14.4 ) (13.4 ) 6.4 7.3 (18.8 ) (20.7 ) Subtotal 117.7 149.6 109.2 133.5 17.6 20.2 Adjustments for amounts included in regulatory assets (115.5 ) (147.1 ) (107.0 ) (131.0 ) (17.6 ) (20.2 ) Total $ 2.2 $ 2.5 $ 2.2 $ 2.5 $ — $ —
Pre-tax amounts amortized from accumulated other comprehensive income into net periodic cost	At September 30, 2018 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic pension cost during fiscal 2019 : Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ 9.2 $ 8.6 $ 0.8 Amortization of prior service (credit) cost (0.9 ) 0.9 (1.8 ) Subtotal 8.3 9.5 (1.0 ) Regulatory adjustment (8.1 ) (9.3 ) 1.0 Total $ 0.2 $ 0.2 $ —
Assumptions used to calculate net periodic cost and benefit obligations.	The assumptions used to calculate net periodic pension costs for Spire Missouri are as follows: 2018 2017 2016 Weighted average discount rate - Spire Missouri East plan 3.75% 3.50% 4.40% Weighted average discount rate - Spire Missouri West plan 3.70% 3.50% 4.50% 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: 2018 2017 2016 Weighted average discount rate 3.65%/3.70% 3.45%/3.50% 4.25%/4.30% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 7.25% 7.25% 7.50% The assumptions used to calculate the benefit obligations are as follows: 2018 2017 Weighted average discount rate - Spire Missouri East plan 4.30% 3.75% Weighted average discount rate - Spire Missouri West plan 4.35% 3.70% Weighted average discount rate - Spire Alabama plans 4.35% 3.65%/3.70% Weighted average rate of future compensation increase 3.00% 3.00%
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 2018 2017 2018 2017 2018 2017 Projected benefit obligation $ 664.6 $ 748.8 $ 473.3 $ 539.6 $ 136.3 $ 148.2 Accumulated benefit obligation 636.0 701.4 446.5 500.4 134.5 142.8 Fair value of plan assets 499.2 531.6 349.1 385.9 101.3 97.9
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 2018 2018 2017 2017 Equity markets 56.4 % 55.3 % 56.4 % 56.8 % Debt securities 43.6 % 42.4 % 43.6 % 42.0 % Cash equivalents — % 2.3 % — % 1.2 % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Alabama 2018 2018 2017 2017 Equity markets 60.0 % 59.4 % 60.0 % 58.5 % Debt securities 29.0 % 28.6 % 29.0 % 28.7 % Other* 11.0 % 12.0 % 11.0 % 12.8 % 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: 2019 2020 2021 2022 2023 2024- 2028 Spire $ 63.0 $ 63.6 $ 60.0 $ 58.4 $ 57.1 $ 266.4 Spire Missouri 50.3 50.2 46.0 43.8 41.9 184.8 Spire Alabama 10.0 10.7 11.2 11.8 12.3 65.5
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 2018 2017 2016 2018 2017 2016 2018 2017 2016 Service cost – benefits earned during the period $ 9.4 $ 11.0 $ 10.9 $ 9.0 $ 10.4 $ 10.6 $ 0.2 $ 0.3 $ 0.3 Interest cost on accumulated postretirement benefit obligation 8.6 8.6 10.2 6.9 6.8 8.1 1.5 1.6 2.1 Expected return on plan assets (13.9 ) (13.6 ) (13.5 ) (9.6 ) (9.0 ) (8.5 ) (4.1 ) (4.4 ) (5.0 ) Amortization of prior service cost (credit) (0.1 ) — 0.3 0.3 0.2 0.3 (0.4 ) (0.2 ) — Amortization of actuarial loss (gain) 0.8 2.5 3.6 0.9 2.6 3.8 (0.1 ) (0.1 ) (0.2 ) Special termination benefits — — 2.6 — — 2.6 — — — Subtotal 4.8 8.5 14.1 7.5 11.0 16.9 (2.9 ) (2.8 ) (2.8 ) Regulatory adjustment 2.2 (3.2 ) (6.6 ) 3.9 (1.5 ) (4.8 ) (1.8 ) (1.8 ) (1.8 ) Net postretirement benefit cost $ 7.0 $ 5.3 $ 7.5 $ 11.4 $ 9.5 $ 12.1 $ (4.7 ) $ (4.6 ) $ (4.6 )
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 2018 2017 2016 2018 2017 2016 2018 2017 2016 Current year actuarial (gain) loss $ (45.1 ) $ (34.1 ) $ 0.8 $ (47.1 ) $ (28.5 ) $ 1.4 $ 1.6 $ (4.5 ) $ (0.6 ) Amortization of actuarial (loss) gain (0.8 ) (2.5 ) (3.6 ) (0.9 ) (2.6 ) (3.8 ) 0.1 0.1 0.2 Current year prior service credit — (1.4 ) (1.8 ) — — — — (1.4 ) (1.8 ) Amortization of prior service (cost) credit 0.1 — (0.3 ) (0.3 ) (0.2 ) (0.3 ) 0.4 0.2 — Subtotal (45.8 ) (38.0 ) (4.9 ) (48.3 ) (31.3 ) (2.7 ) 2.1 (5.6 ) (2.2 ) Regulatory adjustment 45.8 38.0 4.9 48.3 31.3 2.7 (2.1 ) 5.6 2.2 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 2018 2017 2018 2017 2018 2017 Benefit obligation, beginning of year $ 238.5 $ 259.2 $ 192.5 $ 207.9 $ 40.6 $ 45.4 Service cost 9.4 11.0 9.0 10.4 0.2 0.3 Interest cost 8.6 8.6 6.9 6.8 1.5 1.6 Actuarial (gain) loss (37.5 ) (22.1 ) (41.1 ) (20.9 ) 3.1 — Plan amendments — (1.4 ) — — — (1.4 ) Curtailments — 0.4 — — — — Retiree drug subsidy program 0.2 0.3 0.1 0.3 0.1 — Benefits paid (11.1 ) (17.5 ) (8.6 ) (12.0 ) (2.4 ) (5.3 ) Benefit obligation, end of year $ 208.1 $ 238.5 $ 158.8 $ 192.5 $ 43.1 $ 40.6
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 2018 2017 2018 2017 2018 2017 Fair value of plan assets at beginning of year $ 265.5 $ 246.4 $ 174.9 $ 159.7 $ 86.4 $ 82.8 Actual return on plan assets 21.5 26.2 15.6 16.8 5.6 8.9 Employer contributions 7.6 10.4 7.6 10.4 — — Benefits paid (11.1 ) (17.5 ) (8.6 ) (12.0 ) (2.4 ) (5.3 ) Fair value of plan assets, end of year $ 283.5 $ 265.5 $ 189.5 $ 174.9 $ 89.6 $ 86.4 Funded status of plans, end of year $ 75.4 $ 27.0 $ 30.7 $ (17.6 ) $ 46.5 $ 45.8
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 2018 2017 2018 2017 2018 2017 Current assets $ — $ 1.4 $ — $ 1.4 $ — $ — Noncurrent assets 92.0 47.0 45.5 1.2 46.5 45.8 Current liabilities (0.5 ) (0.4 ) (0.5 ) (0.4 ) — — Noncurrent liabilities (16.1 ) (21.0 ) (14.3 ) (19.8 ) — — Total $ 75.4 $ 27.0 $ 30.7 $ (17.6 ) $ 46.5 $ 45.8 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 2018 2017 2018 2017 2018 2017 Net actuarial loss (gain) $ (44.4 ) $ 1.5 $ (35.7 ) $ 12.3 $ (8.0 ) $ (9.7 ) Prior service credit (6.6 ) (6.6 ) (4.0 ) (3.7 ) (2.6 ) (2.9 ) Subtotal (51.0 ) (5.1 ) (39.7 ) 8.6 (10.6 ) (12.6 ) Adjustments for amounts included in regulatory assets 51.0 5.1 39.7 (8.6 ) 10.6 12.6 Total $ — $ — $ — $ — $ — $ —
Pre-tax amounts amortized from accumulated other comprehensive income into net periodic cost	At September 30, 2018 , the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic postretirement benefit cost during fiscal 2019: Spire Spire Missouri Spire Alabama Amortization of net actuarial loss $ (0.5 ) $ (0.5 ) $ — Amortization of prior service (credit) cost (0.1 ) 0.3 (0.4 ) Subtotal (0.6 ) (0.2 ) (0.4 ) Regulatory adjustment 0.6 0.2 0.4 Total $ — $ — $ —
Assumptions used to calculate net periodic cost and benefit obligations.	The assumptions used to calculate the accumulated postretirement benefit obligations are as follows: 2018 2017 Weighted average discount rate - Spire Alabama plans 4.30% 3.80% Weighted average discount rate - Spire Missouri East plans 4.30% 3.60% Weighted average discount rate - Spire Missouri West plans 4.30% 3.60% Weighted average rate of future compensation increase - Spire Missouri East plans 3.00% 3.00% The assumptions used to calculate net periodic postretirement benefit costs for Spire Missouri are as follows: 2018 2017 2016 Weighted average discount rate - Spire Missouri East plans 3.60% 3.15% 4.00% Weighted average discount rate - Spire Missouri West plans 3.60% 3.45% 4.30% 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% 5.75%/7.75% 6.00%/7.75% Expected long-term rate of return on plan assets - Spire Missouri West plans 5.75% 5.50% 4.75% The assumptions used to calculate net periodic postretirement benefit costs for Spire Alabama are as follows: 2018 2017 2016 Weighted average discount rate 3.80% 3.60% 4.50% Expected long-term rate of return on plan assets 3.75%/6.00% 4.00%/6.25% 4.50%/7.25%
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 2018 Actual 2017 Actual Equity securities 60.0 % 58.8 % 59.0 % Debt securities 40.0 % 39.1 % 39.4 % Other (cash and cash equivalents held to make benefit payments) — % 2.1 % 1.6 % Total 100.0 % 100.0 % 100.0 % Spire Alabama Target 2018 Actual 2017 Actual Equity securities 60.0 % 60.0 % 60.1 % Debt securities 40.0 % 40.0 % 39.9 % 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: 2019 2020 2021 2022 2023 2024- 2028 Spire $ 14.2 $ 15.3 $ 16.3 $ 16.9 $ 17.9 $ 93.9 Spire Missouri 10.8 11.8 12.8 13.4 14.3 76.4 Spire Alabama 3.0 3.1 3.1 3.1 3.2 15.1
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: 2018 2017 Medical cost trend assumed for next year - Spire Missouri 7.00% 7.25% Medical cost trend assumed for next year - Spire Alabama 7.00% 7.25% 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 2025 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 $ 1.4 $ (1.3 ) $ 1.2 $ (1.1 ) $ 0.1 $ (0.1 ) Accumulated postretirement benefit obligation 8.4 (7.7 ) 6.0 (5.6 ) 1.6 (1.5 )
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 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, 2018 Cash and cash equivalents $ 35.2 $ — $ — $ 35.2 Equity mutual funds - U.S. — 8.4 — 8.4 Equity mutual funds - international — 4.1 — 4.1 Debt securities: U.S. bond mutual funds — 64.9 — 64.9 U.S. government 31.7 3.0 — 34.7 U.S. corporate 152.1 — — 152.1 U.S. municipal 3.6 3.0 — 6.6 International 43.9 — — 43.9 Derivatives and margin (payable) (0.8 ) — — (0.8 ) Total $ 265.7 $ 83.4 $ — $ 349.1 As of September 30, 2017 Cash and cash equivalents $ 31.7 $ — $ — $ 31.7 Equity mutual funds - U.S. — 11.9 — 11.9 Equity mutual funds - international — 5.7 — 5.7 Debt securities: U.S. bond mutual funds — 68.5 — 68.5 U.S. government 33.2 4.5 — 37.7 U.S. corporate 183.7 — — 183.7 U.S. 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 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, 2018 Cash and cash equivalents $ 3.5 $ — $ — $ 3.5 U.S. stock/bond mutual funds 186.0 — — 186.0 Total $ 189.5 $ — $ — $ 189.5 As of September 30, 2017 Cash and cash equivalents $ 3.9 $ — $ — $ 3.9 U.S. stock/bond mutual funds 171.0 — — 171.0 Total $ 174.9 $ — $ — $ 174.9 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, 2018 Cash and cash equivalents $ 10.4 $ — $ — $ 10.4 Equity mutual funds - U.S. 28.8 8.6 — 37.4 Equity mutual funds - international 14.0 — — 14.0 Debt securities: U.S. bond mutual funds 24.2 — — 24.2 U.S. government — 1.8 — 1.8 International — 4.7 — 4.7 103-12 Direct Filing Entities — 8.8 — 8.8 Total $ 77.4 $ 23.9 $ — $ 101.3 As of September 30, 2017 Cash and cash equivalents $ 3.4 $ — $ — $ 3.4 Equity mutual funds - U.S. 28.4 9.1 — 37.5 Equity mutual funds - international 25.2 3.7 — 28.9 Debt securities: U.S. bond mutual funds 23.2 — — 23.2 International — 4.9 — 4.9 Total $ 80.2 $ 17.7 $ — $ 97.9 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, 2018 U.S. stock/bond mutual funds $ — $ 74.5 $ — $ 74.5 International fund — 15.1 — 15.1 Total $ — $ 89.6 $ — $ 89.6 As of September 30, 2017 U.S. stock/bond mutual funds $ — $ 71.7 $ — $ 71.7 International fund — 14.7 — 14.7 Total $ — $ 86.4 $ — $ 86.4

INFORMATION BY OPERATING SEGM_2

INFORMATION BY OPERATING SEGMENT (Tables)	12 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of operating segment information	Gas Utility Gas Marketing Other Eliminations Consolidated 2018 Revenues from external customers $ 1,888.0 $ 71.6 $ 5.4 $ — $ 1,965.0 Intersegment revenues 0.4 — 11.1 (11.5 ) — Total Operating Revenues 1,888.4 71.6 16.5 (11.5 ) 1,965.0 Operating Expenses Gas Utility Natural and propane gas 842.6 — — (72.5 ) 770.1 Other operation and maintenance 464.1 — — (8.5 ) 455.6 Depreciation and amortization 167.0 — — — 167.0 Taxes, other than income taxes 152.5 — — — 152.5 Total Gas Utility Operating Expenses 1,626.2 — — (81.0 ) 1,545.2 Gas Marketing and Other * — 37.8 32.8 69.5 140.1 Total Operating Expenses 1,626.2 37.8 32.8 (11.5 ) 1,685.3 Operating Income (Loss) $ 262.2 $ 33.8 $ (16.3 ) $ — $ 279.7 Net Economic Earnings (Loss) $ 183.1 $ 22.9 $ (22.3 ) $ — $ 183.7 Capital Expenditures $ 457.7 $ — $ 41.7 $ — $ 499.4 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 * Operating Expenses for “Gas Marketing and Other” include depreciation and amortization for Gas Marketing ( $0.0 for 2018 , $0.1 for 2017 , and $0.1 for 2016 ) and for Other ( $1.4 for 2018 , $0.5 for 2017 , and $0.5 for 2016 ). Total Assets at End of Year 2018 2017 2016 Gas Utility $ 5,606.7 $ 5,551.2 $ 5,184.7 Gas Marketing 295.3 246.2 205.0 Other 2,508.0 2,239.5 1,836.6 Eliminations (1,566.4 ) (1,490.2 ) (1,161.9 ) Total Assets $ 6,843.6 $ 6,546.7 $ 6,064.4
Schedule of the reconciliation of consolidated net economic earnings to consolidated net income	Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings 2018 2017 2016 Net Income $ 214.2 $ 161.6 $ 144.2 Adjustments, pre-tax: Missouri regulatory adjustments 30.6 — — Unrealized (gain) loss on energy-related derivatives (4.0 ) 6.0 (0.1 ) Lower of cost or market inventory adjustments — — 0.2 Realized gain on economic hedges prior to the sale of the physical commodity (0.3 ) (0.3 ) (1.6 ) Acquisition, divestiture and restructuring activities 13.6 4.0 9.2 Income tax effect of adjustments (10.3 ) (3.7 ) (2.8 ) Effect of the Tax Cuts and Jobs Act (60.1 ) — — Net Economic Earnings $ 183.7 $ 167.6 $ 149.1

REGULATORY MATTERS (Tables)

REGULATORY MATTERS (Tables)	12 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
Schedule of regulatory assets	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 2018 2017 2018 2017 Pension and postretirement benefit costs $ 148.4 $ 170.5 $ 148.4 $ 170.5 Future income taxes due from customers 96.3 198.5 94.4 198.5 Other 15.1 11.3 15.1 11.3 Total Regulatory Assets Not Earning a Return $ 259.8 $ 380.3 $ 257.9 $ 380.3 The following regulatory assets and regulatory liabilities were reflected in the Balance Sheets as of September 30, 2018 and 2017 . 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 2018 2017 2018 2017 2018 2017 Regulatory Assets: Current: Pension and postretirement benefit costs $ 30.2 $ 42.2 $ 21.9 $ 34.9 $ 7.3 $ 7.2 Unamortized purchased gas adjustments 8.2 102.6 1.0 57.4 6.4 45.2 Other 34.4 30.7 7.8 3.3 12.5 12.2 Total Current Regulatory Assets 72.8 175.5 30.7 95.6 26.2 64.6 Noncurrent: Future income taxes due from customers 96.3 170.5 94.4 170.5 — — Pension and postretirement benefit costs 364.9 404.7 292.5 322.7 64.8 72.6 Cost of removal 133.4 123.3 — — 133.4 123.3 Unamortized purchased gas adjustments — 9.9 — 9.9 — — Energy efficiency 32.8 29.0 32.8 29.0 — — Other 42.4 53.7 21.4 25.7 3.3 1.1 Total Noncurrent Regulatory Assets 669.8 791.1 441.1 557.8 201.5 197.0 Total Regulatory Assets $ 742.6 $ 966.6 $ 471.8 $ 653.4 $ 227.7 $ 261.6 Regulatory Liabilities: Current: Rate Stabilization and Equalization (“RSE”) adjustment $ — $ 1.4 $ — $ — $ — $ 1.4 Refundable negative salvage 5.2 8.2 — — 5.2 8.2 Unamortized purchased gas adjustments 2.9 1.0 1.9 — — — Other 27.6 12.0 14.8 2.7 2.4 2.4 Total Current Regulatory Liabilities 35.7 22.6 16.7 2.7 7.6 12.0 Noncurrent: Deferred taxes due to customers 178.3 — 161.1 — — — Pension and postretirement benefit costs 27.8 32.2 — — 27.8 32.2 Refundable negative salvage — 4.1 — — — 4.1 Accrued cost of removal 63.6 83.8 39.8 54.5 — — Unamortized purchased gas adjustments 4.7 1.9 4.7 1.9 — — Other 80.2 35.2 69.3 24.8 3.5 3.3 Total Noncurrent Regulatory Liabilities 354.6 157.2 274.9 81.2 31.3 39.6 Total Regulatory Liabilities $ 390.3 $ 179.8 $ 291.6 $ 83.9 $ 38.9 $ 51.6
Schedule of regulatory liabilities	The following regulatory assets and regulatory liabilities were reflected in the Balance Sheets as of September 30, 2018 and 2017 . 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 2018 2017 2018 2017 2018 2017 Regulatory Assets: Current: Pension and postretirement benefit costs $ 30.2 $ 42.2 $ 21.9 $ 34.9 $ 7.3 $ 7.2 Unamortized purchased gas adjustments 8.2 102.6 1.0 57.4 6.4 45.2 Other 34.4 30.7 7.8 3.3 12.5 12.2 Total Current Regulatory Assets 72.8 175.5 30.7 95.6 26.2 64.6 Noncurrent: Future income taxes due from customers 96.3 170.5 94.4 170.5 — — Pension and postretirement benefit costs 364.9 404.7 292.5 322.7 64.8 72.6 Cost of removal 133.4 123.3 — — 133.4 123.3 Unamortized purchased gas adjustments — 9.9 — 9.9 — — Energy efficiency 32.8 29.0 32.8 29.0 — — Other 42.4 53.7 21.4 25.7 3.3 1.1 Total Noncurrent Regulatory Assets 669.8 791.1 441.1 557.8 201.5 197.0 Total Regulatory Assets $ 742.6 $ 966.6 $ 471.8 $ 653.4 $ 227.7 $ 261.6 Regulatory Liabilities: Current: Rate Stabilization and Equalization (“RSE”) adjustment $ — $ 1.4 $ — $ — $ — $ 1.4 Refundable negative salvage 5.2 8.2 — — 5.2 8.2 Unamortized purchased gas adjustments 2.9 1.0 1.9 — — — Other 27.6 12.0 14.8 2.7 2.4 2.4 Total Current Regulatory Liabilities 35.7 22.6 16.7 2.7 7.6 12.0 Noncurrent: Deferred taxes due to customers 178.3 — 161.1 — — — Pension and postretirement benefit costs 27.8 32.2 — — 27.8 32.2 Refundable negative salvage — 4.1 — — — 4.1 Accrued cost of removal 63.6 83.8 39.8 54.5 — — Unamortized purchased gas adjustments 4.7 1.9 4.7 1.9 — — Other 80.2 35.2 69.3 24.8 3.5 3.3 Total Noncurrent Regulatory Liabilities 354.6 157.2 274.9 81.2 31.3 39.6 Total Regulatory Liabilities $ 390.3 $ 179.8 $ 291.6 $ 83.9 $ 38.9 $ 51.6
Off-system sales	Before April 19, 2018, the customer share of such income was 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, the customer share was 100%. 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%

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Sep. 30, 2018
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 2018 2017 2016 2019 2020 2021 2022 2023 Later Total Spire $ 10.0 $ 9.7 $ 11.9 $ 9.7 $ 7.8 $ 6.7 $ 6.5 $ 6.5 $ 41.3 $ 78.5 Spire Missouri 3.6 4.8 4.3 1.3 0.6 0.3 0.1 — — 2.3 Spire Alabama 4.7 4.6 3.7 4.1 2.9 2.1 2.1 2.1 0.7 14.0

INTERIM FINANCIAL INFORMATION_2

INTERIM FINANCIAL INFORMATION (UNAUDITED) (Tables)	12 Months Ended
	Sep. 30, 2018
Quarterly Financial Information [Line Items]
Schedule of Quarterly Financial Information	Three Months Ended Dec. 31 March 31 June 30 Sept. 30 Fiscal Year 2018 Total Operating Revenues $ 561.8 $ 813.4 $ 350.6 $ 239.2 Operating Income (Loss) 105.1 141.8 52.4 (19.6 ) Net Income (Loss) 116.0 98.2 25.9 (25.9 ) Basic Earnings (Loss) Per Share of Common Stock $ 2.40 $ 2.03 $ 0.52 $ (0.51 ) Diluted Earnings (Loss) Per Share of Common Stock $ 2.39 $ 2.03 $ 0.52 $ (0.51 ) 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 )
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 2018 Total Operating Revenues $ 392.3 $ 533.2 $ 215.5 $ 144.6 Operating Income (Loss) 74.8 52.1 21.0 (6.6 ) Net Income (Loss) 89.4 38.4 11.5 (10.0 ) 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
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 2018 Total Operating Revenues $ 120.8 $ 218.3 $ 100.3 $ 61.3 Operating Income (Loss) 19.0 78.2 12.3 (10.9 ) Net Income (Loss) (49.6 ) 55.6 6.3 (11.0 ) 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 )

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)	1 Months Ended			12 Months Ended
	Oct. 31, 2018USD ($)	May 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2018operating_segment
Related Party Transaction [Line Items]
Number of operating segments | operating_segment				2
Natural Gas Storage Facility
Related Party Transaction [Line Items]
Percentage of voting interest acquired		100.00%	80.00%	80.00%
Consideration		$ 12,200,000	$ 24,800,000
Subsequent Event | Natural Gas Storage Facility
Related Party Transaction [Line Items]
Percentage of voting interest acquired	20.00%
Consideration	$ 17,000,000

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant, And Equipment (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Spire Missouri
Property, Plant and Equipment [Line Items]
Average annual depreciation and amortization expense percentage	3.00%	3.00%	3.00%
Spire Alabama
Property, Plant and Equipment [Line Items]
Composite depreciation rate	3.10%	3.10%	3.10%

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accrued Capital Expenditures (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Accruals for capital expenditures	$ 62.1	$ 41	$ 30.4
Spire Missouri
Related Party Transaction [Line Items]
Accruals for capital expenditures	36.7	28.9	14.8
Spire Alabama
Related Party Transaction [Line Items]
Accruals for capital expenditures	$ 8.9	$ 9.4	$ 6.8

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Asset retirement obligations [Roll forward]
Asset retirement obligations, beginning of year	$ 296.6	$ 206.4
Liabilities incurred during the period	5.5	5.5
Liabilities settled during the period	(11.2)	(4.6)
Accretion	12.7	9.1
Revisions in estimated cash flows	16.9	80.2
Business combinations	0.6	0
Asset retirement obligations, end of year	321.1	296.6
Spire Missouri
Asset retirement obligations [Roll forward]
Asset retirement obligations, beginning of year	158.6	75.2
Liabilities incurred during the period	0.6	0.3
Liabilities settled during the period	(8.9)	(1.1)
Accretion	6.6	3.6
Revisions in estimated cash flows	17.2	80.6
Business combinations	0	0
Asset retirement obligations, end of year	174.1	158.6
Spire Alabama
Asset retirement obligations [Roll forward]
Asset retirement obligations, beginning of year	128.4	120.1
Liabilities incurred during the period	3.5	5.2
Liabilities settled during the period	(1.8)	(1.9)
Accretion	5.6	5
Revisions in estimated cash flows	0	0
Business combinations	0	0
Asset retirement obligations, end of year	$ 135.7	$ 128.4

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Natural Gas And Propane Gas (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Difference between replacement cost of gas storage and inventory basis amount	$ 14.5	$ 20.8

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Business Combinations (Details) - USD ($)	Sep. 12, 2016	May 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Working capital settlement payment				$ 0	$ (3,800,000)	$ 317,700,000
Total Operating Revenues				1,965,000,000	1,740,700,000	1,632,400,000
Net Income				$ 214,200,000	$ 161,600,000	$ 153,900,000
Basic Earnings Per Share of Common Stock (in dollars per share)				$ 4.35	$ 3.44	$ 3.48
Diluted Earnings Per Share of Common Stock (in dollars per share)				$ 4.33	$ 3.43	$ 3.46
Spire EnergySouth Inc
Business Acquisition [Line Items]
Percentage of voting interest acquired	100.00%
Working capital settlement payment	$ 313,900,000
Total Operating Revenues				$ 102,100,000	$ 95,500,000	$ 3,300,000
Net Income				$ 13,800,000	$ 9,400,000	$ (200,000)
Natural Gas Storage Facility
Business Acquisition [Line Items]
Percentage of voting interest acquired		100.00%	80.00%	80.00%
Consideration		$ 12,200,000	$ 24,800,000
Payments to acquire business			16,000,000
Non-interest-bearing note			10,000,000
Non-interest-bearing note, value			$ 8,800,000

SUMMARY OF SIGNIFICANT ACCOU_10

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018
Goodwill [Roll Forward]
Beginning balance	$ 1,164.9	$ 946
Goodwill		218.9
Acquisition	6.7
Ending balance	1,171.6	1,164.9
Goodwill	1,164.9	946	$ 1,171.6
Operating Segments | Gas Utility
Goodwill [Roll Forward]
Beginning balance	210.2	210.2
Goodwill		0
Acquisition	0
Ending balance	210.2	210.2
Goodwill	210.2	210.2	210.2
Operating Segments | Gas Marketing
Goodwill [Roll Forward]
Beginning balance	0	0
Goodwill		0
Acquisition	0
Ending balance	0	0
Goodwill	0	0	0
Other
Goodwill [Roll Forward]
Beginning balance	954.7	735.8
Goodwill		218.9
Acquisition	6.7
Ending balance	961.4	954.7
Goodwill	$ 954.7	$ 735.8	$ 961.4

SUMMARY OF SIGNIFICANT ACCOU_11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Spire Missouri
Related Party Transaction [Line Items]
Accrued unbilled revenues	$ 29.7	$ 30.1
Spire Alabama
Related Party Transaction [Line Items]
Accrued unbilled revenues	$ 0	$ 1.9

SUMMARY OF SIGNIFICANT ACCOU_12

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash Equivalents, And Restricted Cash (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Oct. 25, 2018
Restructuring Cost and Reserve [Line Items]
Number of months of the original maturity of debt instruments purchased	3 months
Restricted cash	$ 17
Subsequent Event | Natural Gas Storage Facility
Restructuring Cost and Reserve [Line Items]
Percentage of voting interest		20.00%

SUMMARY OF SIGNIFICANT ACCOU_13

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Gross Receipts and Sales Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Schedule of Gross Receipts Taxes [Line Items]
Gross Receipts taxes recorded in regulated gas distribution operating revenues	$ 98.2	$ 84.6	$ 75.5
Spire Missouri
Schedule of Gross Receipts Taxes [Line Items]
Gross Receipts taxes recorded in regulated gas distribution operating revenues	68.9	60.7	57.4
Spire Alabama
Schedule of Gross Receipts Taxes [Line Items]
Gross Receipts taxes recorded in regulated gas distribution operating revenues	$ 25.4	$ 19.5	$ 17.9

SUMMARY OF SIGNIFICANT ACCOU_14

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Transactions with Affiliates (Details) - Affiliated Entity - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Spire Marketing | Regulated Operation | Spire Missouri
Related Party Transaction [Line Items]
Revenue from related parties	$ 71.5	$ 74.4	$ 46.3
Spire Missouri | Regulated Operation | Spire Marketing
Related Party Transaction [Line Items]
Revenue from related parties	0.3	7.8	1.9
Laclede Pipeline Company | Unregulated Operation | Spire Missouri
Related Party Transaction [Line Items]
Revenue from related parties	$ 1	$ 1	$ 1

SUMMARY OF SIGNIFICANT ACCOU_15

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounts Receivable and Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance at beginning of year	$ 18.3	$ 20.5	$ 14.2
Additions charged to expense	14.6	10.6	6.5
Net deductions	(10.5)	(12.8)	(0.2)
Allowance at end of year	22.4	18.3	20.5
Spire Missouri
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance at beginning of year	14.1	16.1	10
Additions charged to expense	11.9	10.1	6.2
Net deductions	(10)	(12.1)	(0.1)
Allowance at end of year	16	14.1	16.1
Spire Alabama
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance at beginning of year	2.6	3.3	4.2
Additions charged to expense	2.1	0.2	0.6
Net deductions	(0.8)	(0.9)	(1.5)
Allowance at end of year	$ 3.9	$ 2.6	$ 3.3

SUMMARY OF SIGNIFICANT ACCOU_16

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Finance Receivables (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivable, net	$ 13.1	$ 12.5
Spire Alabama
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for collection	90 days
Threshold period past due for write-off of financing receivable	12 months
Financing Receivables, Equal to Greater than 90 Days Past Due | Spire Alabama
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivable 90 days past due	$ 0.4	$ 0.4

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
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	$ 9.4
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)	34,922	35,514	30,712
Vested restricted stock withheld for tax withholding obligations, weighted average price (in dollars per share)	$ 81.65	$ 63.83	$ 57.29
Fair value, restricted stock	$ 10.5	$ 8.9	$ 6.3
Actual tax benefit realized	$ 4	$ 3.3	$ 2.4
Restricted Stock Awards | Performance Vesting
Restricted Stock Awards [Abstract]
Granted (in shares)	87,960
Granted, weighted average grant date fair value (in dollars per share)	$ 79.88
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)		$ 58.45	$ 62.38
Maximum amount of shares pursuant to restricted stock awards		200.00%
Number of shares issued for maximum performance payout (in shares)	532,164
Restricted Stock Awards | Time Vesting
Restricted Stock Awards [Abstract]
Granted (in shares)	47,780
Granted, weighted average grant date fair value (in dollars per share)	$ 73.85
Restricted Stock Awards | Time Vesting | Executive Officers and Key Employees
Restricted Stock Awards [Abstract]
Granted (in shares)	37,980
Granted, weighted average grant date fair value (in dollars per share)	$ 76.60	$ 63.05	59.40
Restricted Stock Awards | Time Vesting | Non Employee Directors
Restricted Stock Awards [Abstract]
Granted (in shares)	9,800
Granted, weighted average grant date fair value (in dollars per share)	$ 63.20	$ 63.45	$ 63.93
Stock Option Awards
Stock Option Awards [Abstract]
Cash received from the exercise of stock options			$ 0.7
Intrinsic value of exercised			$ 0.7

STOCK-BASED COMPENSATION - Rest

STOCK-BASED COMPENSATION - Restricted Stock and Restricted Stock Unit Activity (Details) - Restricted Stock Awards	12 Months Ended
	Sep. 30, 2018$ / sharesshares
Performance Vesting
Shares/ Units
Nonvested at beginning of period (in shares) | shares	282,015
Granted (in shares) | shares	87,960
Vested (in shares) | shares	(81,933)
Forfeited (in shares) | shares	(21,960)
Nonvested at end of period (in shares) | shares	266,082
Weighted Average Grant Date Fair Value Per Share
Nonvested at beginning of period (in dollars per share) | $ / shares	$ 56.32
Granted (in dollars per share) | $ / shares	79.88
Vested (in dollars per share) | $ / shares	47.80
Forfeited (in dollars per share) | $ / shares	56.73
Nonvested at end of period (in dollars per share) | $ / shares	$ 66.69
Time Vesting
Shares/ Units
Nonvested at beginning of period (in shares) | shares	110,940
Granted (in shares) | shares	47,780
Vested (in shares) | shares	(47,928)
Forfeited (in shares) | shares	(7,192)
Nonvested at end of period (in shares) | shares	103,600
Weighted Average Grant Date Fair Value Per Share
Nonvested at beginning of period (in dollars per share) | $ / shares	$ 55.85
Granted (in dollars per share) | $ / shares	73.85
Vested (in dollars per share) | $ / shares	53.48
Forfeited (in dollars per share) | $ / shares	65.25
Nonvested at end of period (in dollars per share) | $ / shares	$ 64.60

STOCK-BASED COMPENSATION - Fair

STOCK-BASED COMPENSATION - Fair Value Measurement Assumptions (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	1.76%	1.39%	1.14%
Expected dividend yield of stock	0.00%	0.00%	0.00%
Expected volatility of stock	16.00%	16.30%	15.00%
Vesting period	2 years 10 months 24 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, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total compensation cost	$ 6.9	$ 7.4	$ 6.7
Compensation cost capitalized	(1.3)	(3.3)	(2.2)
Prior period disallowed stock compensation capitalization	6.9	0	0
Compensation cost recognized in net income	12.5	4.1	4.5
Income tax benefit recognized in net income	(4)	(1.5)	(1.7)
Compensation cost recognized in net income, net of income tax	$ 8.5	$ 2.6	$ 2.8

EARNINGS PER COMMON SHARE (Deta

EARNINGS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	Apr. 03, 2017	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Basic Earnings Per Share:
Net income		$ (25.9)	$ 25.9	$ 98.2	$ 116	$ (13.3)	$ 21.7	$ 108	$ 45.2	$ 214.2	$ 161.6	$ 144.2
Less: Income allocated to participating securities										0.5	0.4	0.5
Net Income Available to Common Shareholders										$ 213.7	$ 161.2	$ 143.7
Weighted Average Shares Outstanding, Basic (in shares)										49,100	46,900	44,100
Earnings Per Share of Common Stock (in dollars per share)		$ (0.51)	$ 0.52	$ 2.03	$ 2.40	$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ 4.35	$ 3.44	$ 3.26
Diluted Earnings per Share:
Net income		$ (25.9)	$ 25.9	$ 98.2	$ 116	$ (13.3)	$ 21.7	$ 108	$ 45.2	$ 214.2	$ 161.6	$ 144.2
Less: Income allocated to participating securities										0.5	0.4	0.5
Net Income Available to Common Shareholders										$ 213.7	$ 161.2	$ 143.7
Weighted Average Shares Outstanding, Basic (in shares)										49,100	46,900	44,100
Dilutive Effect of Stock Options, Restricted Stock, and Restricted Stock Units (in shares)										200	100	200
Weighted Average Diluted Shares (in shares)										49,300	47,000	44,300
Earnings Per Share of Common Stock (in dollars per share)		$ (0.51)	$ 0.52	$ 2.03	$ 2.39	$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ 4.33	$ 3.43	$ 3.24
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
Calculation excludes certain outstanding shares (shown in millions by period at the right) attributable to stock units subject to performance or market conditions and restricted stock, which could have a dilutive effect in the future
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares excluded from calculation of diluted EPS (in shares)										400	500	300

SHAREHOLDERS' EQUITY - Narrativ

SHAREHOLDERS' EQUITY - Narrative (Details) - USD ($)	Apr. 03, 2017	May 17, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2014	Nov. 12, 2018	May 10, 2018	Jun. 20, 2014
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Issuance of stock (in shares)		2,185,000
Issuance of common stock		$ 133,200,000	$ 153,000,000	$ 145,500,000	$ 133,200,000
Shares of common stock issued (in shares)	2,504,684
SEC effective shelf registration Form S-3 sale and issuance authorization under the dividend reinvestment and stock purchase program (in shares)								2,300,000	250,000
SEC effective shelf registration Form S-3 remaining and available for issuance under the dividend reinvestment and stock purchase program (in shares)			221,107					68.75
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			$ 1,097,600,000	$ 1,010,800,000
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			$ 500,000,000
Spire Alabama
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Issuance of common stock					$ (29,000,000)
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
Subsequent Event
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
SEC effective shelf registration Form S-3 remaining and available for issuance under the dividend reinvestment and stock purchase program (in shares)							216,678
Junior Subordinated Debt
Accumulated other comprehensive income (loss), net of income taxes [Line Items]
Proceeds from convertible debt						$ 142,000,000

SHAREHOLDERS' EQUITY - Schedule

SHAREHOLDERS' EQUITY - Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	$ 1,991.3	$ 1,768.2	$ 1,573.6
Other comprehensive income (loss)	2.5	7.4	(2.2)
Reclassification of certain income tax effects	0.7
BALANCE	2,255.4	1,991.3	1,768.2
Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	1,171	1,068.5	1,037.8
Other comprehensive income (loss)	0.4	0.1	(0.1)
Reclassification of certain income tax effects	(0.3)
BALANCE	1,259.9	1,171	1,068.5
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	4.9	(2.3)
Other comprehensive income (loss)	2	7.2
Reclassification of certain income tax effects	1
BALANCE	7.9	4.9	(2.3)
Net Unrealized Gains (Losses) on Cash Flow Hedges | Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	0.1	0.1
Other comprehensive income (loss)	(0.1)	0
Reclassification of certain income tax effects	0
BALANCE	0	0.1	0.1
Defined Benefit Pension and Other Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(1.5)	(1.8)
Other comprehensive income (loss)	0.3	0.3
Reclassification of certain income tax effects	(0.3)
BALANCE	(1.5)	(1.5)	(1.8)
Defined Benefit Pension and Other Postretirement Benefit Plans | Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(1.6)	(1.8)
Other comprehensive income (loss)	0.3	0.2
Reclassification of certain income tax effects	(0.3)
BALANCE	(1.6)	(1.6)	(1.8)
Net Unrealized Losses on Available-for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(0.2)	(0.1)
Other comprehensive income (loss)	0.2	(0.1)
Reclassification of certain income tax effects	0
BALANCE	0	(0.2)	(0.1)
Net Unrealized Losses on Available-for-Sale Debt Securities | Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(0.2)	(0.1)
Other comprehensive income (loss)	0.2	(0.1)
Reclassification of certain income tax effects	0
BALANCE	0	(0.2)	(0.1)
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	3.2	(4.2)	(2)
Other comprehensive income (loss)	2.5	7.4	(2.2)
Reclassification of certain income tax effects	0.7
BALANCE	6.4	3.2	(4.2)
AOCI | Spire Missouri
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE	(1.7)	(1.8)	(1.7)
Other comprehensive income (loss)	0.4	0.1	(0.1)
Reclassification of certain income tax effects	(0.3)
BALANCE	$ (1.6)	$ (1.7)	$ (1.8)

LONG-TERM DEBT - Maturities of

LONG-TERM DEBT - Maturities of Long-term Debt (Details) $ in Millions	Sep. 30, 2018USD ($)
Maturities on long-term debt [Abstract]
2,019	$ 175.5
2,020	43.2
2,021	57
2,022	52
2,023	332.3
Spire Missouri
Maturities on long-term debt [Abstract]
2,019	50
2,020	0
2,021	0
2,022	0
2,023	305
Spire Alabama
Maturities on long-term debt [Abstract]
2,019	0
2,020	40
2,021	0
2,022	50
2,023	$ 0

LONG-TERM DEBT - Narrative (Det

LONG-TERM DEBT - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Long-term debt	$ 2,092,000,000
Interest expense, net	$ 2,600,000	$ 800,000	$ 200,000
Weighted average interest rate	2.40%	1.50%
Spire Missouri
Debt Instrument [Line Items]
Long-term debt	$ 880,000,000
Interest expense, net	900,000	$ 500,000	$ 200,000
Regulatory preferred stock and debt securities issuance, amount authorized	500,000,000
Spire Alabama
Debt Instrument [Line Items]
Long-term debt	325,000,000
Subsidiaries
Debt Instrument [Line Items]
Long-term debt	$ 72,000,000

NOTES PAYABLE AND CREDIT AGRE_3

NOTES PAYABLE AND CREDIT AGREEMENTS - Narrative (Details)	12 Months Ended
	Sep. 30, 2018USD ($)	Dec. 14, 2016bank
Spire Missouri
Line of Credit Facility [Line Items]
Long-term debt	$ 975,000,000
Debt term	365 days
Revolving Credit Facility Borrowings
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	0.54
Revolving Credit Facility Borrowings | Spire Missouri
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	$ 475,000,000
Debt to total capitalization ratio	0.49
Revolving Credit Facility Borrowings | Spire Alabama
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	$ 200,000,000
Debt to total capitalization ratio	0.37
Revolving Credit Facility Borrowings | Liabilities | Lender Concentration Risk
Line of Credit Facility [Line Items]
Line of credit facility, number of banks in agreement | bank		11
Spire | Revolving Credit Facility Borrowings
Line of Credit Facility [Line Items]
Line of credit facility borrowing capacity	$ 300,000,000
Subsidiaries
Line of Credit Facility [Line Items]
Notes outstanding	$ 540,500,000

NOTES PAYABLE AND CREDIT AGRE_4

NOTES PAYABLE AND CREDIT AGREEMENTS - Spire Short-term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 408.6
Weighted average interest rate	2.00%
Minimum borrowing outstanding	$ 146
Maximum borrowing outstanding	632.9
Borrowings outstanding	$ 553.6	$ 477.3
Weighted average interest rate	2.40%	1.50%
Commercial Paper Borrowings
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 408.5
Weighted average interest rate	2.00%
Minimum borrowing outstanding	$ 146
Maximum borrowing outstanding	632.9
Borrowings outstanding	$ 553.6	$ 477.3
Weighted average interest rate	2.40%	1.50%
Revolving Credit Facility Borrowings
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 0.1
Weighted average interest rate	2.80%
Minimum borrowing outstanding	$ 0
Maximum borrowing outstanding	25
Borrowings outstanding	$ 0	$ 0
Weighted average interest rate	0.00%	0.00%

NOTES PAYABLE AND CREDIT AGRE_5

NOTES PAYABLE AND CREDIT AGREEMENTS - Spire Missouri and Alabama Short-term Borrowings (Details) - USD ($)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 408,600,000
Weighted average interest rate	2.00%
Minimum borrowing outstanding	$ 146,000,000
Maximum borrowing outstanding	632,900,000
Borrowings outstanding	$ 553,600,000	$ 477,300,000
Weighted average interest rate	2.40%	1.50%
Spire Missouri | Borrowings
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 210,500,000
Weighted average interest rate	2.10%
Minimum borrowing outstanding	$ 101,500,000
Maximum borrowing outstanding	345,300,000
Borrowings outstanding	$ 345,300,000	$ 203,000,000
Weighted average interest rate	2.30%	1.50%
Spire Alabama | Borrowings
Short-term Debt [Line Items]
Weighted average borrowings outstanding	$ 103,900,000
Weighted average interest rate	2.00%
Minimum borrowing outstanding	$ 33,600,000
Maximum borrowing outstanding	188,600,000
Borrowings outstanding	$ 142,500,000	$ 169,900,000
Weighted average interest rate	2.30%	1.50%

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 4.4	$ 7.4
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	4.4	7.4
Short-term debt	553.6	477.3
Long-term debt, including current portion	2,075.6	2,095
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	4.4	7.4
Short-term debt	553.6	477.3
Long-term debt, including current portion	2,074	2,210.3
Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2	2.5	$ 2.1	$ 1.7
Spire Missouri | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2	2.5
Short-term debt	345.3	203
Long-term debt, including current portion	874.4	973.9
Spire Missouri | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2	2.5
Short-term debt	345.3	203
Long-term debt, including current portion	906.6	1,056.9
Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0.1	$ 0	$ 7.2
Spire Alabama | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		0.1
Short-term debt	142.5	169.9
Long-term debt, including current portion	322.6	247.8
Spire Alabama | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		0.1
Short-term debt	142.5	169.9
Long-term debt, including current portion	321.7	269.4
Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	4.4	7.4
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	2.5
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	553.6	477.3
Long-term debt, including current portion	2,074	2,210.3
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	345.3	203
Long-term debt, including current portion	906.6	1,056.9
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	142.5	169.9
Long-term debt, including current portion	$ 321.7	$ 269.4

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
ASSETS
Derivative asset after the effects of netting	$ 19	$ 6.2
LIABILITIES
Derivative liability after the effects of netting	6.2	8
Spire Missouri
ASSETS
Derivative asset after the effects of netting	0	0.1
LIABILITIES
Derivative liability after the effects of netting	0	0
Fair Value, Measurements, Recurring
ASSETS
Effects of netting and cash margin receivables/payables	(8.4)	(6.7)
Derivative asset after the effects of netting	48.2	28.7
LIABILITIES
Effects of netting and cash margin receivables/payables	(14.8)	(5.2)
Derivative liability after the effects of netting	6.2	8.1
Fair Value, Measurements, Recurring | Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	(2.7)	(3.4)
Derivative asset after the effects of netting	20.3	22.5
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	32.1	23.1
LIABILITIES
Derivative liability before effects of netting	2.8	3.7
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1) | Spire Missouri
ASSETS
Derivative asset before effects of netting	23	21.8
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	24.5	12.2
LIABILITIES
Derivative liability before effects of netting	18	9.6
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level 2) | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	4.1
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0	0.1
LIABILITIES
Derivative liability before effects of netting	0.2	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
Fair Value, Measurements, Recurring | U.S. stock/bond mutual funds | Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	0	0
Derivative asset after the effects of netting	20.3	22.4
Fair Value, Measurements, Recurring | U.S. stock/bond mutual funds | Quoted Prices in Active Markets (Level 1) | Spire Missouri
ASSETS
Derivative asset before effects of netting	20.3	18.3
Fair Value, Measurements, Recurring | U.S. stock/bond mutual funds | Significant Observable Inputs (Level 2) | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	4.1
Fair Value, Measurements, Recurring | U.S. 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	(2.7)	(3.4)
Derivative asset after the effects of netting	0	0
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.9)	(1.9)
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	2.7	3.4
LIABILITIES
Derivative liability before effects of netting	1.9	1.9
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 | NYMEX gasoline and heating oil contracts | Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables		0
Derivative asset after the effects of netting		0.1
Fair Value, Measurements, Recurring | NYMEX gasoline and heating oil contracts | Quoted Prices in Active Markets (Level 1) | Spire Missouri
ASSETS
Derivative asset before effects of netting		0.1
Fair Value, Measurements, Recurring | NYMEX gasoline and heating oil contracts | Significant Observable Inputs (Level 2) | Spire Missouri
ASSETS
Derivative asset before effects of netting		0
Fair Value, Measurements, Recurring | NYMEX gasoline and heating oil contracts | Significant Unobservable Inputs (Level 3) | Spire Missouri
ASSETS
Derivative asset before effects of netting		0
Fair Value, Measurements, Recurring | Gas Utility | NYMEX gasoline and heating oil contracts
ASSETS
Effects of netting and cash margin receivables/payables		0
Derivative asset after the effects of netting		0.1
Fair Value, Measurements, Recurring | Gas Utility | NYMEX gasoline and heating oil contracts | Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting		0.1
Fair Value, Measurements, Recurring | Gas Utility | NYMEX gasoline and heating oil contracts | Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting		0
Fair Value, Measurements, Recurring | Gas Utility | NYMEX 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 Utility | U.S. stock/bond mutual funds
ASSETS
Effects of netting and cash margin receivables/payables	0	0
Derivative asset after the effects of netting	20.3	22.4
Operating Segments | Fair Value, Measurements, Recurring | Gas Utility | U.S. stock/bond mutual funds | Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	20.3	18.3
Operating Segments | Fair Value, Measurements, Recurring | Gas Utility | U.S. stock/bond mutual funds | Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	0	4.1
Operating Segments | Fair Value, Measurements, Recurring | Gas Utility | U.S. 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	(2.7)	(3.4)
Derivative asset after the effects of netting	0	0
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.9)	(1.9)
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	2.7	3.4
LIABILITIES
Derivative liability before effects of netting	1.9	1.9
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 Marketing | NYMEX/ICE natural gas contracts
ASSETS
Effects of netting and cash margin receivables/payables	(4.2)
Derivative asset after the effects of netting	0
LIABILITIES
Effects of netting and cash margin receivables/payables	(11.4)	(2.1)
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	0.2
LIABILITIES
Derivative liability before effects of netting	0.9	1.8
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	4
LIABILITIES
Derivative liability before effects of netting	10.5	0.3
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		(2.1)
Derivative asset after the effects of netting		0.5
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
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
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	(1.5)	(1.2)
Derivative asset after the effects of netting	16	5.7
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.5)	(1.2)
Derivative liability after the effects of netting	6.2	7.2
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	17.5	6.8
LIABILITIES
Derivative liability before effects of netting	7.5	8.4
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	0.1
LIABILITIES
Derivative liability before effects of netting	0.2	0
Other | Fair Value, Measurements, Recurring | Interest rate swaps
LIABILITIES
Effects of netting and cash margin receivables/payables		0
Derivative liability after the effects of netting		0.9
Other | Fair Value, Measurements, Recurring | Interest rate swaps | Quoted Prices in Active Markets (Level 1)
LIABILITIES
Derivative liability before effects of netting		0
Other | Fair Value, Measurements, Recurring | Interest rate swaps | Significant Observable Inputs (Level 2)
LIABILITIES
Derivative liability before effects of netting		0.9
Other | Fair Value, Measurements, Recurring | Interest rate swaps | Significant Unobservable Inputs (Level 3)
LIABILITIES
Derivative liability before effects of netting		$ 0
Other | Fair Value, Measurements, Recurring | Gas Marketing | U.S. stock/bond mutual funds
ASSETS
Effects of netting and cash margin receivables/payables	0
Derivative asset after the effects of netting	8.9
Other | Fair Value, Measurements, Recurring | Gas Marketing | U.S. stock/bond mutual funds | Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	8.9
Other | Fair Value, Measurements, Recurring | Gas Marketing | U.S. stock/bond mutual funds | Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	0
Other | Fair Value, Measurements, Recurring | Gas Marketing | U.S. stock/bond mutual funds | Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0
Other | Fair Value, Measurements, Recurring | Gas Marketing | Interest rate swaps
ASSETS
Effects of netting and cash margin receivables/payables	0
Derivative asset after the effects of netting	3
Other | Fair Value, Measurements, Recurring | Gas Marketing | Interest rate swaps | Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	0
Other | Fair Value, Measurements, Recurring | Gas Marketing | Interest rate swaps | Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	3
Other | Fair Value, Measurements, Recurring | Gas Marketing | Interest rate swaps | Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	$ 0

DERIVATIVE INSTRUMENTS AND HE_3

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details) MMBTU in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2018USD ($)	Sep. 30, 2018USD ($)MMBTU	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Derivative [Line Items]
Notional amount of non-exchange traded natural gas commodity contracts (in MMBtu) | MMBTU		277.7
Notional amount of non-exchange traded natural gas commodity contracts to be settled during fiscal 2018 (in MMBtu) | MMBTU		196.7
Notional amount of non-exchange traded natural gas commodity contracts to be settled during fiscal 2019 (in MMBtu) | MMBTU		43.1
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2020 (in MMBtu) | MMBTU		30.5
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2021 (in MMBtu) | MMBTU		7.3
Notional amount of non-exchange traded natural gas commodity to be settled during fiscal 2023 (in MMBtu) | MMBTU		0.1
Mark-to-market gain		$ 4	$ (6)	$ 0.1
Cash margin receivables not offset with derivatives		$ 4.1	4
Spire Missouri
Derivative [Line Items]
MMBtu (millions) | MMBTU		38.4
Cash margin receivables not offset with derivatives			3.8	4
Interest rate swaps
Derivative [Line Items]
Notional amount	$ 100
Derivative fixed interest rate	2.7675%
Derivative, term of contract	3 years
Mark-to-market gain		$ 0.5
Derivatives in Cash Flow Hedging Relationships | Interest rate swaps
Derivative [Line Items]
Loss on termination and settlement of interest rate swap		$ 2.5
Gain on settlement of derivative			14.1
Derivatives in Cash Flow Hedging Relationships | Interest rate swaps | Spire EnergySouth Inc
Derivative [Line Items]
Loss on termination and settlement of interest rate swap				0.4
Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Interest rate swaps
Derivative [Line Items]
Notional amount			$ 60	225
Derivative fixed interest rate			2.658%
Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Interest rate swaps | Spire EnergySouth Inc
Derivative [Line Items]
Notional amount				$ 85

DERIVATIVE INSTRUMENTS AND HE_4

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Exchange-Traded/Cleared Derivatives (Details) MMBTU in Thousands	12 Months Ended
	Sep. 30, 2018MMBTU$ / MMBTU
Gas Utility | Natural gas contracts | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Gas Utility | Natural gas contracts | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Gas Marketing | Natural gas contracts | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	250
Avg. Price Per MMBtu | $ / MMBTU	2.98
Gas Marketing | Natural gas contracts | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	10
Avg. Price Per MMBtu | $ / MMBTU	2.86
Short | Gas Utility | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Short | Gas Utility | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Short | Gas Utility | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Short | Gas Utility | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Short | Gas Utility | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Short | Gas Utility | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Short | Gas Marketing | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	7,870
Avg. Price Per MMBtu | $ / MMBTU	3.04
Short | Gas Marketing | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,000
Avg. Price Per MMBtu | $ / MMBTU	2.93
Short | Gas Marketing | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	140
Avg. Price Per MMBtu | $ / MMBTU	2.94
Short | Gas Marketing | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,540
Avg. Price Per MMBtu | $ / MMBTU	2.95
Short | Gas Marketing | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	52,480
Avg. Price Per MMBtu | $ / MMBTU	0.23
Short | Gas Marketing | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	3,800
Avg. Price Per MMBtu | $ / MMBTU	0.25
Long | Gas Utility | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	24,120
Avg. Price Per MMBtu | $ / MMBTU	2.80
Long | Gas Utility | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,680
Avg. Price Per MMBtu | $ / MMBTU	2.69
Long | Gas Utility | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Long | Gas Utility | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0
Long | Gas Marketing | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	9,270
Avg. Price Per MMBtu | $ / MMBTU	2.89
Long | Gas Marketing | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,110
Avg. Price Per MMBtu | $ / MMBTU	2.85
Long | Gas Marketing | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	550
Avg. Price Per MMBtu | $ / MMBTU	2.87
Long | Gas Marketing | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	570
Avg. Price Per MMBtu | $ / MMBTU	2.92
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	49,990
Avg. Price Per MMBtu | $ / MMBTU	0.64
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	3,180
Avg. Price Per MMBtu | $ / MMBTU	0.68
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	920
Avg. Price Per MMBtu | $ / MMBTU	0.52
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	160
Avg. Price Per MMBtu | $ / MMBTU	0.52

DERIVATIVE INSTRUMENTS AND HE_5

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Gains (Losses) on Derivative Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net hedging gain (loss) arising during the period	$ 3.9	$ 11.5	$ (4)
Derivatives in Cash Flow Hedging Relationships | Cash Flow Hedging
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	1.5	0	(1.1)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.5	0.3
Derivatives in Cash Flow Hedging Relationships | Cash Flow Hedging | Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net hedging gain (loss) arising during the period	3.9	11.5	(4)
Derivatives in Cash Flow Hedging Relationships | Cash Flow Hedging | Natural gas contracts
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income	0	(0.3)	(0.6)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0	0.2
Derivatives in Cash Flow Hedging Relationships | Cash Flow Hedging | Natural gas contracts | Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net hedging gain (loss) arising during the period	0	0	(0.6)
Derivatives in Cash Flow Hedging Relationships | 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	(0.4)	4.3
Ineffective portion of gain (loss) on derivatives recognized in income	0	0	0.1
Derivatives in Cash Flow Hedging Relationships | 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	0.1	(4.9)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0	0.1
Derivatives in Cash Flow Hedging Relationships | Cash Flow Hedging | Gasoline and heating oil contracts | Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net hedging gain (loss) arising during the period	0	0.1	0
Derivatives in Cash Flow Hedging Relationships | 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	0.1	0.2	(0.5)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0	0.1
Derivatives in Cash Flow Hedging Relationships | Cash Flow Hedging | Interest rate swaps | Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net hedging gain (loss) arising during the period	3.9	11.4	(3.4)
Derivatives in Cash Flow Hedging Relationships | 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	1.4	0.1	0
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.5	0
Not Designated as Hedging Instrument
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	2.1	(3.7)	10.6
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	10.2	0.7	12.3
Not Designated as Hedging Instrument | Natural gas commodity contracts | Gas Marketing Operating Expenses
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives	(8.1)	0	0
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	$ 0	$ (4.4)	$ (1.7)

DERIVATIVE INSTRUMENTS AND HE_6

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	$ 27.4	$ 13
Fair value of liability derivatives presented above	21	13.3
Derivatives in Cash Flow Hedging Relationships
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	3
Fair value of liability derivatives presented above	0
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	24.4	12.3
Fair value of liability derivatives presented above	21	12.2
Other | Interest rate swaps | Derivatives in Cash Flow Hedging Relationships | Derivative Instrument Assets
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	3	0
Fair value of liability derivatives presented above	0	0.9
Gas Utility | Operating Segments | Gasoline and heating oil contracts | Derivatives in Cash Flow Hedging Relationships | 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
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	2.7	3.4
Fair value of liability derivatives presented above	1.9	1.9
Gas Marketing | Derivatives in Cash Flow Hedging Relationships
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0.7
Fair value of liability derivatives presented above		1.1
Gas Marketing | Operating Segments | Natural gas contracts | Derivatives in Cash Flow Hedging Relationships | 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 | Derivatives in Cash Flow Hedging Relationships | Deferred Charges – Other
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above		0.3
Fair value of liability derivatives presented above		0
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	3.8	1.7
Fair value of liability derivatives presented above	10.7	1.4
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	0.4	0.3
Fair value of liability derivatives presented above	0.7	0.5
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	10.9	5.3
Fair value of liability derivatives presented above	1	0.1
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	6.3	0.4
Fair value of liability derivatives presented above	0.2	0
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	0.3	0.8
Fair value of liability derivatives presented above	6.3	5
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	0.4
Fair value of liability derivatives presented above	$ 0.2	$ 3.3

DERIVATIVE INSTRUMENTS AND HE_7

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Instruments Reconciliation (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Offsetting Derivative Assets [Abstract]
Fair value of asset derivatives presented above	$ 27.4	$ 13
Fair value of cash margin (payable) receivable offset with derivatives	6.4	(1.5)
Netting of assets and liabilities with the same counterparty	(14.8)	(5.3)
Derivative asset after the effects of netting	19	6.2
Derivative instrument assets	13.3	5.9
Deferred Charges – Other	5.7	0.3
Offsetting Derivative Liabilities [Abstract]
Fair value of liability derivatives presented above	21	13.3
Netting of assets and liabilities with the same counterparty	(14.8)	(5.3)
Derivative liability after the effects of netting	6.2	8
Current Liabilities – Other	6	4.9
Deferred Credits – Other	0.2	3.1
Spire Missouri
Offsetting Derivative Assets [Abstract]
Fair value of asset derivatives presented above	2.7	3.5
Fair value of cash margin (payable) receivable offset with derivatives	(0.8)	(1.5)
Netting of assets and liabilities with the same counterparty	(1.9)	(1.9)
Derivative asset after the effects of netting	0	0.1
Derivative instrument assets	0	0.1
Offsetting Derivative Liabilities [Abstract]
Fair value of liability derivatives presented above	1.9	1.9
Netting of assets and liabilities with the same counterparty	(1.9)	(1.9)
Derivative liability after the effects of netting	$ 0	$ 0

DERIVATIVE INSTRUMENTS AND HE_8

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Open NYMEX Natural Gas Futures Positions (Details) MMBTU in Thousands	12 Months Ended
	Sep. 30, 2018MMBTU$ / MMBTU
Fiscal 2019 | Gas Utility | Natural gas contracts | Long
Derivative [Line Items]
MMBtu (millions)	24,120
Avg. Price Per MMBtu | $ / MMBTU	2.80
Fiscal 2020 | Gas Utility | Natural gas contracts | Long
Derivative [Line Items]
MMBtu (millions)	2,680
Avg. Price Per MMBtu | $ / MMBTU	2.69
Spire Missouri
Derivative [Line Items]
MMBtu (millions)	38,400
Spire Missouri | Fiscal 2019 | Gas Utility | Natural gas contracts | Long
Derivative [Line Items]
MMBtu (millions)	24,120
Avg. Price Per MMBtu | $ / MMBTU	2.80
Spire Missouri | Fiscal 2020 | Gas Utility | Natural gas contracts | Long
Derivative [Line Items]
MMBtu (millions)	2,680
Avg. Price Per MMBtu | $ / MMBTU	2.69

DERIVATIVE INSTRUMENTS AND HE_9

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Effect of Derivative Instruments on the Statement of Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Net hedging gain (loss) arising during the period	$ 3.9	$ 11.5	$ (4)
Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships
Derivative [Line Items]
Effective portion of gain (loss) reclassified from AOCI to income	1.5	0	(1.1)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0.5	0.3
Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Other Comprehensive Income (Loss)
Derivative [Line Items]
Net hedging gain (loss) arising during the period	3.9	11.5	(4)
Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Other Comprehensive Income (Loss) | Gasoline and heating oil contracts
Derivative [Line Items]
Net hedging gain (loss) arising during the period	0	0.1	0
Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Gas Utility Other Operating Expenses | Gasoline and heating oil contracts
Derivative [Line Items]
Effective portion of gain (loss) reclassified from AOCI to income	0.1	0.2	(0.5)
Ineffective portion of gain (loss) on derivatives recognized in income	0	0	0.1
Spire Missouri
Derivative [Line Items]
Net hedging gain (loss) arising during the period	0	0.1	0
Spire Missouri | Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Other Comprehensive Income (Loss) | Gasoline and heating oil contracts
Derivative [Line Items]
Net hedging gain (loss) arising during the period	0	0.1	0
Spire Missouri | Cash Flow Hedging | Derivatives in Cash Flow Hedging Relationships | Gas Utility Other Operating Expenses | Gasoline and heating oil contracts
Derivative [Line Items]
Effective portion of gain (loss) reclassified from AOCI to income	0.1	0.2	(0.5)
Ineffective portion of gain (loss) on derivatives recognized in income	$ 0	$ 0	$ 0.1

DERIVATIVE INSTRUMENTS AND H_10

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Fair Value of Derivative Instruments in the Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Fair value of asset derivatives presented above	$ 27.4	$ 13
Fair value of liability derivatives presented above	21	13.3
Not Designated as Hedging Instrument
Derivative [Line Items]
Fair value of asset derivatives presented above	24.4	12.3
Fair value of liability derivatives presented above	21	12.2
Derivatives in Cash Flow Hedging Relationships
Derivative [Line Items]
Fair value of asset derivatives presented above	3
Fair value of liability derivatives presented above	0
Spire Missouri
Derivative [Line Items]
Fair value of asset derivatives presented above	2.7	3.5
Fair value of liability derivatives presented above	1.9	1.9
Spire Missouri | Gas Utility
Derivative [Line Items]
Fair value of asset derivatives presented above	2.7	3.5
Fair value of liability derivatives presented above	1.9	1.9
Spire Missouri | Not Designated as Hedging Instrument | Accounts Receivable – Other | Gas Utility | Natural gas contracts
Derivative [Line Items]
Fair value of asset derivatives presented above	2.7	3.4
Fair value of liability derivatives presented above	$ 1.9	1.9
Spire Missouri | Derivatives in Cash Flow Hedging Relationships | Gas Utility
Derivative [Line Items]
Fair value of asset derivatives presented above		0.1
Fair value of liability derivatives presented above		0
Spire Missouri | Derivatives in Cash Flow Hedging Relationships | Derivative Instrument Assets | Gas Utility | Gasoline and heating oil contracts
Derivative [Line Items]
Fair value of asset derivatives presented above		0.1
Fair value of liability derivatives presented above		$ 0

DERIVATIVE INSTRUMENTS AND H_11

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Reconciliation to Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Fair value of asset derivatives presented above	$ 27.4	$ 13
Fair value of cash margin (payable) receivable offset with derivatives	(6.4)	1.5
Netting of assets and liabilities with the same counterparty	(14.8)	(5.3)
Derivative asset after the effects of netting	19	6.2
Derivative instrument assets	13.3	5.9
Fair value of liability derivatives presented above	21	13.3
Netting of assets and liabilities with the same counterparty	(14.8)	(5.3)
Derivative liability after the effects of netting	6.2	8
Spire Missouri
Derivative [Line Items]
Fair value of asset derivatives presented above	2.7	3.5
Fair value of cash margin (payable) receivable offset with derivatives	0.8	1.5
Netting of assets and liabilities with the same counterparty	(1.9)	(1.9)
Derivative asset after the effects of netting	0	0.1
Derivative instrument assets	0	0.1
Fair value of liability derivatives presented above	1.9	1.9
Netting of assets and liabilities with the same counterparty	(1.9)	(1.9)
Derivative liability after the effects of netting	$ 0	$ 0

CONCENTRATIONS OF CREDIT RISK (

CONCENTRATIONS OF CREDIT RISK (Details) $ in Millions	Sep. 30, 2018USD ($)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	$ 11.2
Net receivable amount	3.7
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	96.1
Net receivable amount	89.7
Five Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	51.3
Net receivable amount	$ 50.6

INCOME TAXES - Net Provisions f

INCOME TAXES - Net Provisions for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Federal
Current	$ 0	$ 0.1	$ 0.1
Deferred	(22.7)	67.7	62
Investment tax credits	(0.2)	(0.2)	(0.2)
State and local
Current	2.2	0.5	0.6
Deferred	(5.8)	9.5	7
Total income tax (benefit) expense	(26.5)	77.6	69.5
Spire Missouri
Federal
Current	0	0	0
Deferred	(26.1)	42	37.5
Investment tax credits	(0.2)	(0.2)	(0.2)
State and local
Current	0	0	0.1
Deferred	(6.3)	5.7	8
Total income tax (benefit) expense	(32.6)	47.5	45.4
Spire Alabama
Federal
Current	0	0	(0.8)
Deferred	81.5	31.6	29.4
State and local
Current	0	0	0
Deferred	0.1	4.2	3.8
Total income tax (benefit) expense	$ 81.6	$ 35.8	$ 32.4

INCOME TAXES - Effective Income

INCOME TAXES - Effective Income Tax Rate Variation from Stated Tax Rate (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Contingency [Line Items]
Federal income tax statutory rate	24.50%	35.00%	35.00%
State and local income taxes, net of federal income tax benefits	3.40%	2.80%	2.80%
Certain expenses capitalized on books and deducted on tax return	(2.30%)	(2.30%)	(3.40%)
Taxes related to prior years	(0.40%)	(0.90%)	(0.20%)
Tax law changes	(35.90%)	0.00%	0.00%
Amortization of excess deferred taxes	(1.80%)	0.00%	0.00%
Other items – net	(1.60%)	(2.20%)	(1.70%)
Effective income tax rate	(14.10%)	32.40%	32.50%
Spire Missouri
Income Tax Contingency [Line Items]
Federal income tax statutory rate	24.50%	35.00%	35.00%
State and local income taxes, net of federal income tax benefits	3.40%	2.80%	2.80%
Certain expenses capitalized on books and deducted on tax return	(4.60%)	(3.50%)	(4.80%)
Taxes related to prior years	(0.70%)	(1.40%)	(0.20%)
Tax law changes	(50.30%)	0.00%	0.00%
Amortization of excess deferred taxes	(3.60%)	0.00%	0.00%
Other items – net	(2.50%)	(3.30%)	(2.80%)
Effective income tax rate	(33.80%)	29.60%	30.00%
Spire Alabama
Income Tax Contingency [Line Items]
Federal income tax statutory rate	24.50%	35.00%	35.00%
State and local income taxes, net of federal income tax benefits	3.80%	2.80%	2.80%
Tax law changes	70.00%	0.00%	0.00%
Other items – net	0.10%	0.30%	0.10%
Effective income tax rate	98.40%	38.10%	37.90%

INCOME TAXES - Significant Item

INCOME TAXES - Significant Items in Net Deferred Tax Liability (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Deferred tax assets:
Reserves not currently deductible	$ 25.9	$ 31.5
Pension and other postretirement benefits	75.6	58.6
Operating losses	162.7	169.6
Regulatory amount due to customers, net	41.8	0
Other	8.2	26
Deferred tax assets	314.2	285.7
Less: valuation allowance	1.4	0.5
Total deferred tax assets	312.8	285.2
Deferred tax liabilities:
Relating to property	518.3	728.3
Regulatory pension and other postretirement benefits	117.1	108
Deferred gas costs	2.3	30.6
Other	110.9	125.8
Total deferred tax liabilities	748.6	992.7
Net deferred tax liability	435.8	707.5
Spire Missouri
Deferred tax assets:
Reserves not currently deductible	20	25.3
Pension and other postretirement benefits	71.9	52.7
Deferred gas costs	0.5	0
Operating losses	65.2	52
Regulatory amount due to customers, net	38	0
Deferred tax assets	195.6	130
Less: valuation allowance	1.4	0.5
Total deferred tax assets	194.2	129.5
Deferred tax liabilities:
Relating to property	372.6	563.2
Regulatory pension and other postretirement benefits	113.4	108
Deferred gas costs	0	25
Other	69.2	57.1
Total deferred tax liabilities	555.2	753.3
Net deferred tax liability	361	623.8
Spire Alabama
Deferred tax assets:
Reserves not currently deductible	5.3	6
Pension and other postretirement benefits	0	4.4
Goodwill	129.6	214.4
Operating losses	86	88.3
Deferred tax assets	220.9	313.1
Deferred tax liabilities:
Relating to property	111.9	119.3
Regulatory pension and other postretirement benefits	1.8	0
Other	5.4	8.2
Total deferred tax liabilities	119.1	127.5
Net deferred tax asset	$ 101.8	$ 185.6

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Tax Credit Carryforward [Line Items]
Excess accumulated deferred taxes	$ 3,500,000
Federal and state loss carryforwards	711,900,000
Contribution carryforwards	12,900,000
Valuation allowance	1,400,000	$ 500,000
Tax credit carryforwards	2,400,000
Capital loss carryforward	400,000
Unrecognized tax benefits affect on the Company's effective tax rate	3,900,000	5,100,000
Income taxes accrued	0	0
Income tax penalties accrued	0	0
Spire Missouri
Tax Credit Carryforward [Line Items]
Excess accumulated deferred taxes	3,500,000
Federal and state loss carryforwards	309,200,000
Contribution carryforwards	10,900,000
Valuation allowance	1,400,000	500,000
Tax credit carryforwards	2,000,000
Unrecognized tax benefits affect on the Company's effective tax rate	3,600,000	4,800,000
Income taxes accrued	0	0
Income tax penalties accrued	0	$ 0
Spire Alabama
Tax Credit Carryforward [Line Items]
Federal and state loss carryforwards	$ 342,600,000

INCOME TAXES - Impact of Tax Cu

INCOME TAXES - Impact of Tax Cuts and Jobs Act (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Deferred Income Tax Assets And Liabilities [Line Items]
Adjustment to deferred tax liabilities	$ (318.3)
Adjustment to deferred income tax expense	(75)
Adjustment to regulatory assets	(75.9)
Adjustment to regulatory liabilities	167.4
Spire Missouri
Deferred Income Tax Assets And Liabilities [Line Items]
Adjustment to deferred tax liabilities	(285.3)
Adjustment to deferred income tax expense	(57)
Adjustment to regulatory assets	(78.1)
Adjustment to regulatory liabilities	150.2
Spire Alabama
Deferred Income Tax Assets And Liabilities [Line Items]
Adjustment to deferred tax assets	(61)
Adjustment to deferred income tax expense	58.8
Adjustment to regulatory assets	$ 2.2

INCOME TAXES - Unrecognized Tax

INCOME TAXES - Unrecognized Tax Benefit Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, beginning of year	$ 11	$ 10	$ 7.1
Decrease related to tax law changes	(4)	0	0
Increases related to tax positions taken in current year	1.2	2.4	3.4
Reductions due to lapse of applicable statute of limitations	(0.1)	(1.4)	(0.5)
Unrecognized tax benefits, end of year	8.1	11	10
Spire Missouri
Unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, beginning of year	10.7	9.7	6.9
Decrease related to tax law changes	(4)	0	0
Increases related to tax positions taken in current year	1.1	2.4	3.3
Reductions due to lapse of applicable statute of limitations	0	(1.4)	(0.5)
Unrecognized tax benefits, end of year	$ 7.8	$ 10.7	$ 9.7

PENSION PLANS AND OTHER POSTR_3

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Net Periodic Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	$ 20.2	$ 20.5	$ 15.3
Interest cost on projected benefit obligation	27.4	27.9	28
Expected return on plan assets	(37)	(38.5)	(34.9)
Amortization of prior service cost (credit)	(0.9)	1	0.4
Amortization of actuarial loss	10.9	12.5	8
Loss on lump-sum settlements and curtailments	18.6	17.9	3.3
Special termination benefits	0	0.9	1.6
Subtotal	39.2	42.2	21.7
Regulatory adjustment	37.4	(2.4)	17.8
Net benefit cost	76.6	39.8	39.5
Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	9.4	11	10.9
Interest cost on projected benefit obligation	8.6	8.6	10.2
Expected return on plan assets	(13.9)	(13.6)	(13.5)
Amortization of prior service cost (credit)	(0.1)	0	0.3
Amortization of actuarial loss	0.8	2.5	3.6
Special termination benefits	0	0	2.6
Subtotal	4.8	8.5	14.1
Regulatory adjustment	2.2	(3.2)	(6.6)
Net benefit cost	7	5.3	7.5
Spire Missouri | Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	12.7	12.7	10
Interest cost on projected benefit obligation	19.5	19.5	21.7
Expected return on plan assets	(27.2)	(28.1)	(26.7)
Amortization of prior service cost (credit)	0.9	1	0.4
Amortization of actuarial loss	9.4	10.7	7.9
Loss on lump-sum settlements and curtailments	16.1	13.5	0
Special termination benefits	0	0	1.6
Subtotal	31.4	29.3	14.9
Regulatory adjustment	32.1	(4.1)	11.7
Net benefit cost	63.5	25.2	26.6
Spire Missouri | Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	9	10.4	10.6
Interest cost on projected benefit obligation	6.9	6.8	8.1
Expected return on plan assets	(9.6)	(9)	(8.5)
Amortization of prior service cost (credit)	0.3	0.2	0.3
Amortization of actuarial loss	0.9	2.6	3.8
Special termination benefits	0	0	2.6
Subtotal	7.5	11	16.9
Regulatory adjustment	3.9	(1.5)	(4.8)
Net benefit cost	11.4	9.5	12.1
Spire Alabama | Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	6.4	6.2	5.3
Interest cost on projected benefit obligation	5.5	6.1	6.3
Expected return on plan assets	(6.5)	(7.2)	(8.2)
Amortization of prior service cost (credit)	(1.8)	0	0
Amortization of actuarial loss	1.5	1.8	0.1
Loss on lump-sum settlements and curtailments	2.4	4.6	3.3
Special termination benefits	0	0	0
Subtotal	7.5	11.5	6.8
Regulatory adjustment	4.5	1.8	6.1
Net benefit cost	12	13.3	12.9
Spire Alabama | Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	0.2	0.3	0.3
Interest cost on projected benefit obligation	1.5	1.6	2.1
Expected return on plan assets	(4.1)	(4.4)	(5)
Amortization of prior service cost (credit)	(0.4)	(0.2)	0
Amortization of actuarial loss	(0.1)	(0.1)	(0.2)
Special termination benefits	0	0	0
Subtotal	(2.9)	(2.8)	(2.8)
Regulatory adjustment	(1.8)	(1.8)	(1.8)
Net benefit cost	$ (4.7)	$ (4.6)	$ (4.6)

PENSION PLANS AND OTHER POSTR_4

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Changes in Plan Assets and Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of actuarial loss	$ (0.4)	$ (0.4)	$ 0.3
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial (gain) loss	(1.4)	14.1	46.8
Amortization of actuarial loss	(10.9)	(12.5)	(8)
Acceleration of loss recognized due to settlement	(18.5)	(18.2)	(3.3)
Current year service (credit) cost	(0.1)	0	5
Current year prior year service cost	0	(20.7)	0
Transfer due to merger	0.1	0	0
Amortization of prior service cost	(2.9)	(1)	(0.4)
Amortization of transition asset	1.8	0	0
Subtotal	(31.9)	(38.3)	40.1
Regulatory adjustment	31.6	38	(39.8)
Total recognized in OCI	(0.3)	(0.3)	0.3
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial (gain) loss	(45.1)	(34.1)	0.8
Amortization of actuarial loss	(0.8)	(2.5)	(3.6)
Current year prior year service cost	0	(1.4)	(1.8)
Amortization of prior service cost	0.1	0	(0.3)
Subtotal	(45.8)	(38)	(4.9)
Regulatory adjustment	45.8	38	4.9
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	(0.4)	(0.3)	0.3
Spire Missouri | Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial (gain) loss	2.2	14.8	21.6
Amortization of actuarial loss	(9.4)	(10.7)	(7.9)
Acceleration of loss recognized due to settlement	(16.1)	(13.5)	0
Current year service (credit) cost	0	0	5
Current year prior year service cost	0	0	0
Transfer due to merger	0.1	0	0
Amortization of prior service cost	(0.9)	(1)	(0.4)
Amortization of transition asset	0	0	0
Subtotal	(24.1)	(10.4)	18.3
Regulatory adjustment	23.8	10.1	(18)
Total recognized in OCI	(0.3)	(0.3)	0.3
Spire Missouri | Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial (gain) loss	(47.1)	(28.5)	1.4
Amortization of actuarial loss	(0.9)	(2.6)	(3.8)
Current year prior year service cost	0	0	0
Amortization of prior service cost	(0.3)	(0.2)	(0.3)
Subtotal	(48.3)	(31.3)	(2.7)
Regulatory adjustment	48.3	31.3	2.7
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 (gain) loss	(0.6)	3.3	25.2
Amortization of actuarial loss	(1.5)	(1.8)	(0.1)
Acceleration of loss recognized due to settlement	(2.4)	(4.5)	(3.3)
Current year service (credit) cost	0	0	0
Current year prior year service cost	0	(20.7)	0
Transfer due to merger	0	0	0
Amortization of prior service cost	0	0	0
Amortization of transition asset	1.8	0	0
Subtotal	(2.7)	(23.7)	21.8
Regulatory adjustment	2.7	23.7	(21.8)
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 (gain) loss	1.6	(4.5)	(0.6)
Amortization of actuarial loss	0.1	0.1	0.2
Current year prior year service cost	0	(1.4)	(1.8)
Amortization of prior service cost	0.4	0.2	0
Subtotal	2.1	(5.6)	(2.2)
Regulatory adjustment	(2.1)	5.6	2.2
Total recognized in OCI	$ 0	$ 0	$ 0

PENSION PLANS AND OTHER POSTR_5

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Apr. 19, 2018	Mar. 07, 2018	Apr. 11, 2017	Jan. 01, 2011	Feb. 20, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement benefits paid			$ 62.2
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%
Regulatory assets		$ 742.6	966.6
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided		15 years
Anticipated Contributions to pension plans for qualified trust		$ 27.1
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
Other Plans [Abstract]
401(K) plans, cost of defined contributions		$ 0	0	$ 0
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
Regulatory assets		471.8	653.4
Other Plans [Abstract]
401(K) plans, cost of defined contributions		9	8.4	8.2
Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory assets		227.7	261.6
Other Plans [Abstract]
401(K) plans, cost of defined contributions		3	2.7	2.3
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									$ 9.9
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement benefits paid		82.8	62.2
Employer contributions		58.9	$ 41.3
Pension Plans | Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rates	4.20%		3.70%
Settlement benefits paid		65.5	$ 43.5
Employer contributions		$ 36.9	$ 29.4
Targeted allocation of plan assets		100.00%	100.00%
Pension Plans | Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rates		4.20%	3.65%
Settlement benefits paid		$ 17.3	$ 18.7	$ 16.6
Employer contributions		$ 20.1	$ 11.9
Targeted allocation of plan assets		100.00%	100.00%
Other Pension Plan | Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rates	4.15%		3.75%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		$ 7.6	$ 10.4
Anticipated contributions to the postretirement plans for qualified trusts		1.9
Anticipated payment directly to participants in postretirement plan		$ 0.5
Other Postretirement Benefits Plan [Member] | Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rates		3.00%	3.00%
Employer contributions		$ 7.6	$ 10.4
Targeted allocation of plan assets		100.00%
Other Postretirement Benefits Plan [Member] | Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		$ 0	$ 0
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%	56.40%
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 | Other Postretirement Benefits Plan [Member] | Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets		60.00%
Equity markets | Other Postretirement Benefits Plan [Member] | 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%	43.60%
Debt securities | Pension Plans | Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets		29.00%	29.00%
Debt securities | Other Postretirement Benefits Plan [Member] | Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets		40.00%
Debt securities | Other Postretirement Benefits Plan [Member] | Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted allocation of plan assets		40.00%
Pension Cost | MoPSC | Infrastructure System Replacement Surcharge | Spire Missouri West
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory assets						$ 5.5	$ 9.9
Pension Cost | MoPSC | Infrastructure System Replacement Surcharge | Spire Missouri East
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory assets						29	15.5
Pension and Other Postretirement Benefits | Spire Missouri West
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of assets	$ 26.2	$ 26.2
Pension and Other Postretirement Benefits | Spire Missouri East
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided	8 years	8 years
Amortization of assets	$ 173	$ 173
Pension and Other Postretirement Benefits | Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		$ 20.1	$ 11.9
Postretirement Benefit Costs | MoPSC | Infrastructure System Replacement Surcharge | Spire Missouri East
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Regulatory assets					$ 8.6	$ 8.6	$ 9.5

PENSION PLANS AND OTHER POSTR_6

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Benefit Obligation Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Settlement benefits paid		$ (62.2)
Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	$ 748.8	794.7
Service cost	20.2	20.5	$ 15.3
Interest cost	27.4	27.9	28
Actuarial (gain) loss	34.9	0.9
Plan amendments	(2)	(20.7)
Plan mergers	0	0
Settlement loss	7.6	14.6
Special termination benefits	0	0.9
Settlement benefits paid	(82.8)	(62.2)
Regular benefits paid	(19.7)	(26)
Benefit obligation, end of year	664.6	748.8	794.7
Accumulated benefit obligation, end of year	636	701.4
Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	238.5	259.2
Service cost	9.4	11	10.9
Interest cost	8.6	8.6	10.2
Actuarial (gain) loss	(37.5)	(22.1)
Plan amendments	0	(1.4)
Curtailments	0	0.4
Retiree drug subsidy program	0.2	0.3
Regular benefits paid	(11.1)	(17.5)
Benefit obligation, end of year	208.1	238.5	259.2
Spire Missouri | Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	539.6	560
Service cost	12.7	12.7	10
Interest cost	19.5	19.5	21.7
Actuarial (gain) loss	26	0.5
Plan amendments	0	0
Plan mergers	(0.3)	0
Settlement loss	7.6	12.2
Special termination benefits	0	0
Settlement benefits paid	(65.5)	(43.5)
Regular benefits paid	(14.3)	(20.8)
Benefit obligation, end of year	473.3	539.6	560
Accumulated benefit obligation, end of year	446.5	500.4
Spire Missouri | Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	192.5	207.9
Service cost	9	10.4	10.6
Interest cost	6.9	6.8	8.1
Actuarial (gain) loss	(41.1)	(20.9)
Plan amendments	0	0
Curtailments	0	0
Retiree drug subsidy program	0.1	0.3
Regular benefits paid	(8.6)	(12)
Benefit obligation, end of year	158.8	192.5	207.9
Spire Alabama | Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	148.2	174.3
Service cost	6.4	6.2	5.3
Interest cost	5.5	6.1	6.3
Actuarial (gain) loss	3.8	(1.6)
Plan amendments	0	(20.7)
Plan mergers	0	0
Settlement loss	0	2.4
Special termination benefits	0	0
Settlement benefits paid	(17.3)	(18.7)	(16.6)
Regular benefits paid	(2.7)	(3)
Benefit obligation, end of year	136.3	148.2	174.3
Accumulated benefit obligation, end of year	134.5	142.8
Spire Alabama | Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	40.6	45.4
Service cost	0.2	0.3	0.3
Interest cost	1.5	1.6	2.1
Actuarial (gain) loss	3.1	0
Plan amendments	0	(1.4)
Curtailments	0	0
Retiree drug subsidy program	0.1	0
Regular benefits paid	(2.4)	(5.3)
Benefit obligation, end of year	$ 43.1	$ 40.6	$ 45.4

PENSION PLANS AND OTHER POSTR_7

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Settlement benefits paid		$ (62.2)
Pension Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	$ 531.6	540.5
Actual return on plan assets	11.2	38
Employer contributions	58.9	41.3
Divestitures	0	0
Settlement benefits paid	(82.8)	(62.2)
Regular benefits paid	(19.7)	(26)
Fair value of plan assets, end of year	499.2	531.6	$ 540.5
Funded status of plans, end of year	(165.4)	(217.2)
Postretirement Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	265.5	246.4
Actual return on plan assets	21.5	26.2
Employer contributions	7.6	10.4
Regular benefits paid	(11.1)	(17.5)
Fair value of plan assets, end of year	283.5	265.5	246.4
Funded status of plans, end of year	75.4	27
Spire Missouri | Pension Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	385.9	395.7
Actual return on plan assets	6.4	25.1
Employer contributions	36.9	29.4
Divestitures	(0.3)	0
Settlement benefits paid	(65.5)	(43.5)
Regular benefits paid	(14.3)	(20.8)
Fair value of plan assets, end of year	349.1	385.9	395.7
Funded status of plans, end of year	(124.2)	(153.7)
Spire Missouri | Postretirement Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	174.9	159.7
Actual return on plan assets	15.6	16.8
Employer contributions	7.6	10.4
Regular benefits paid	(8.6)	(12)
Fair value of plan assets, end of year	189.5	174.9	159.7
Funded status of plans, end of year	30.7	(17.6)
Spire Alabama
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, end of year	8.8
Spire Alabama | Pension Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	97.9	100
Actual return on plan assets	3.3	7.7
Employer contributions	20.1	11.9
Divestitures	0	0
Settlement benefits paid	(17.3)	(18.7)	(16.6)
Regular benefits paid	(2.7)	(3)
Fair value of plan assets, end of year	101.3	97.9	100
Funded status of plans, end of year	(35)	(50.3)
Spire Alabama | Postretirement Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	86.4	82.8
Actual return on plan assets	5.6	8.9
Employer contributions	0	0
Regular benefits paid	(2.4)	(5.3)
Fair value of plan assets, end of year	89.6	86.4	$ 82.8
Funded status of plans, end of year	$ 46.5	$ 45.8

PENSION PLANS AND OTHER POSTR_8

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent liabilities	$ (180.2)	$ (237.4)
Pension Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.6)	(0.5)
Noncurrent liabilities	(164.8)	(216.7)
Total	(165.4)	(217.2)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	132.1	163
Prior service (credit) cost	(14.4)	(13.4)
Subtotal	117.7	149.6
Adjustments for amounts included in regulatory assets	(115.5)	(147.1)
Total	2.2	2.5
Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.5)	(0.4)
Noncurrent liabilities	(16.1)	(21)
Total	75.4	27
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	(44.4)	1.5
Prior service (credit) cost	(6.6)	(6.6)
Subtotal	(51)	(5.1)
Adjustments for amounts included in regulatory assets	51	5.1
Total	0	0
Spire Missouri
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent liabilities	(136.9)	(173)
Spire Missouri | Pension Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.6)	(0.5)
Noncurrent liabilities	(123.6)	(153.2)
Total	(124.2)	(153.7)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	102.8	126.2
Prior service (credit) cost	6.4	7.3
Subtotal	109.2	133.5
Adjustments for amounts included in regulatory assets	(107)	(131)
Total	2.2	2.5
Spire Missouri | Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(0.5)	(0.4)
Noncurrent liabilities	(14.3)	(19.8)
Total	30.7	(17.6)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	(35.7)	12.3
Prior service (credit) cost	(4)	(3.7)
Subtotal	(39.7)	8.6
Adjustments for amounts included in regulatory assets	39.7	(8.6)
Total	0	0
Spire Alabama
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent liabilities	(35)	(50.2)
Spire Alabama | Pension Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	0	0
Noncurrent liabilities	(35)	(50.3)
Total	(35)	(50.3)
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	36.4	40.9
Prior service (credit) cost	(18.8)	(20.7)
Subtotal	17.6	20.2
Adjustments for amounts included in regulatory assets	(17.6)	(20.2)
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	46.5	45.8
Pre-tax amounts recognized in accumulated other comprehensive income not yet recognized as components of net periodic pension cost consist of:
Net actuarial loss	(8)	(9.7)
Prior service (credit) cost	(2.6)	(2.9)
Subtotal	(10.6)	(12.6)
Adjustments for amounts included in regulatory assets	10.6	12.6
Total	0	0
Current Asset [Member] | Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	0	1.4
Current Asset [Member] | Spire Missouri | Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	0	1.4
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	92	47
Noncurrent Asset [Member] | Spire Missouri | Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	45.5	1.2
Noncurrent Asset [Member] | Spire Alabama | Postretirement Plans
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Noncurrent assets	$ 46.5	$ 45.8

PENSION PLANS AND OTHER POSTR_9

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Pre-tax Amortization from AOCI (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Pension Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	$ 9.2
Amortization of prior service (credit) cost	(0.9)
Subtotal	8.3
Regulatory adjustment	(8.1)
Total	0.2
Postretirement Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	(0.5)
Amortization of prior service (credit) cost	(0.1)
Subtotal	(0.6)
Regulatory adjustment	0.6
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	8.6
Amortization of prior service (credit) cost	0.9
Subtotal	9.5
Regulatory adjustment	(9.3)
Total	0.2
Spire Missouri | Postretirement Plans
Pre-tax amounts are expected to be amortized from accumulated other comprehensive income [Abstract]
Amortization of net actuarial loss	(0.5)
Amortization of prior service (credit) cost	0.3
Subtotal	(0.2)
Regulatory adjustment	0.2
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	0.8
Amortization of prior service (credit) cost	(1.8)
Subtotal	(1)
Regulatory adjustment	1
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 POST_10

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Assumptions Used to Calculate Net Periodic Cost and Benefit Obligations (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2018
Spire Missouri East | Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.75%	3.50%	4.40%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.75%
Spire Missouri East | Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.60%	3.15%	4.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.60%
Spire Missouri East | 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 East | 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%
Spire Missouri West | Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.70%	3.50%	4.50%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.35%	3.70%
Spire Missouri West | Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.60%	3.45%	4.30%
Expected long-term rate of return on plan assets	5.75%	5.50%	4.75%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.60%
Spire Alabama | Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Expected long-term rate of return on plan assets	7.25%	7.25%	7.50%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.35%
Weighted average rate of future compensation increase	4.20%	3.65%
Spire Alabama | Pension Plans | Minimum
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.65%	3.45%	4.25%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate		3.65%
Spire Alabama | Pension Plans | Maximum
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.70%	3.50%	4.30%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate		3.70%
Spire Alabama | Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.80%	3.60%	4.50%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.80%
Spire Alabama | Postretirement Plans | Minimum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	3.75%	4.00%	4.50%
Spire Alabama | Postretirement Plans | Maximum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	6.00%	6.25%	7.25%
Spire Missouri | Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
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 rate of future compensation increase		3.70%		4.20%
Spire Missouri | Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%
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 POST_11

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Projected Benefit Obligation (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 664.6	$ 748.8
Accumulated benefit obligation	636	701.4
Fair value of plan assets	499.2	531.6
Spire Missouri
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	473.3	539.6
Accumulated benefit obligation	446.5	500.4
Fair value of plan assets	349.1	385.9
Spire Alabama
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	136.3	148.2
Accumulated benefit obligation	134.5	142.8
Fair value of plan assets	$ 101.3	$ 97.9

PENSION PLANS AND OTHER POST_12

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Targeted and Actual Plan Assets by Category (Details)	Sep. 30, 2018	Sep. 30, 2017
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	59.40%	58.50%
Spire Alabama | Pension Plans | Debt securities
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	29.00%	29.00%
Actual allocation of plan assets	28.60%	28.70%
Spire Alabama | Pension Plans | Other
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	11.00%	11.00%
Actual allocation of plan assets	12.00%	12.80%
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	60.00%	60.10%
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	40.00%	39.90%
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%	56.40%
Actual allocation of plan assets	55.30%	56.80%
Spire Missouri | Pension Plans | Debt securities
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	43.60%	43.60%
Actual allocation of plan assets	42.40%	42.00%
Spire Missouri | Pension Plans | Cash equivalents
Targeted and actual plan assets by category [Abstract]
Targeted allocation of plan assets	0.00%	0.00%
Actual allocation of plan assets	2.30%	1.20%
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	58.80%	59.00%
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	39.10%	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	2.10%	1.60%

PENSION PLANS AND OTHER POST_13

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Expected Future Benefit Payments (Details) $ in Millions	Sep. 30, 2018USD ($)
Pension Plans
Expected benefit payments [Abstract]
2,019	$ 63
2,020	63.6
2,021	60
2,022	58.4
2,023	57.1
2024 - 2028	266.4
Postretirement Plans
Expected benefit payments [Abstract]
2,019	14.2
2,020	15.3
2,021	16.3
2,022	16.9
2,023	17.9
2024 - 2028	93.9
Spire Missouri | Pension Plans
Expected benefit payments [Abstract]
2,019	50.3
2,020	50.2
2,021	46
2,022	43.8
2,023	41.9
2024 - 2028	184.8
Spire Missouri | Postretirement Plans
Expected benefit payments [Abstract]
2,019	10.8
2,020	11.8
2,021	12.8
2,022	13.4
2,023	14.3
2024 - 2028	76.4
Spire Alabama | Pension Plans
Expected benefit payments [Abstract]
2,019	10
2,020	10.7
2,021	11.2
2,022	11.8
2,023	12.3
2024 - 2028	65.5
Spire Alabama | Postretirement Plans
Expected benefit payments [Abstract]
2,019	3
2,020	3.1
2,021	3.1
2,022	3.1
2,023	3.2
2024 - 2028	$ 15.1

PENSION PLANS AND OTHER POST_14

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, 2018	Sep. 30, 2017
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	2,025	2,023
Assumed 1% change in the assumed medical cost trend rate [Abstract]
Effect of 1% increase on net periodic postretirement benefit cost	$ 1.4
Effect of 1% decrease on net periodic postretirement benefit cost	(1.3)
Effect of 1% increase on accumulated postretirement benefit obligation	8.4
Effect of 1% decrease on accumulated postretirement benefit obligation	$ (7.7)
Spire Missouri
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Medical cost trend assumed for next year	7.00%	7.25%
Assumed 1% change in the assumed medical cost trend rate [Abstract]
Effect of 1% increase on net periodic postretirement benefit cost	$ 1.2
Effect of 1% decrease on net periodic postretirement benefit cost	(1.1)
Effect of 1% increase on accumulated postretirement benefit obligation	6
Effect of 1% decrease on accumulated postretirement benefit obligation	$ (5.6)
Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Medical cost trend assumed for next year	7.00%	7.25%
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	1.6
Effect of 1% decrease on accumulated postretirement benefit obligation	$ (1.5)

PENSION PLANS AND OTHER POST_15

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Fair Value Measurements of Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	$ 499.2	$ 531.6	$ 540.5
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	50.6	37.3
Pension Plans | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	63.9	67.5
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	24.8	48.6
Pension Plans | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	100.7	102.9
Pension Plans | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.3	37.7
Pension Plans | U.S. corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	152.1	183.7
Pension Plans | U.S. municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	6.6	4.2
Pension Plans | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	50.9	52.3
Pension Plans | Derivatives and margin (payable)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(0.8)	(2.6)
Pension Plans | 103-12 Direct Filing Entities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	13.1
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	380.3	414.8
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	50.6	37.3
Pension Plans | Quoted Prices in Active Markets (Level 1) | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	42.7	42.1
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	20.7	37.4
Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	35.8	34.4
Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	31.7	33.2
Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	152.1	183.7
Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.6	4.2
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	43.9	45.1
Pension Plans | Quoted Prices in Active Markets (Level 1) | Derivatives and margin (payable)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(0.8)	(2.6)
Pension Plans | Quoted Prices in Active Markets (Level 1) | 103-12 Direct Filing Entities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
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	118.9	116.8
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 - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	21.2	25.4
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	4.1	11.2
Pension Plans | Significant Observable Inputs (Level 2) | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	64.9	68.5
Pension Plans | Significant Observable Inputs (Level 2) | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	5.6	4.5
Pension Plans | Significant Observable Inputs (Level 2) | U.S. 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) | U.S. municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3	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	7.2
Pension Plans | Significant Observable Inputs (Level 2) | Derivatives and margin (payable)
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) | 103-12 Direct Filing Entities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	13.1
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
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 - U.S.
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 - 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) | U.S. 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) | U.S. 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) | U.S. 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) | U.S. 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) | Derivatives and margin (payable)
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) | 103-12 Direct Filing Entities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	283.5	265.5	246.4
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	3.7	4
Postretirement Plans | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	264.7	245.8
Postretirement Plans | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	15.1	15.7
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	193.9	179.1
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	3.7	4
Postretirement Plans | Quoted Prices in Active Markets (Level 1) | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	190.2	174.1
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	1
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	89.6	86.4
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 - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	74.5	71.7
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	15.1	14.7
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 - U.S.
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	349.1	385.9	395.7
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	35.2	31.7
Spire Missouri | Pension Plans | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	8.4	11.9
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	4.1	5.7
Spire Missouri | Pension Plans | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	64.9	68.5
Spire Missouri | Pension Plans | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	34.7	37.7
Spire Missouri | Pension Plans | U.S. corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	152.1	183.7
Spire Missouri | Pension Plans | U.S. municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	6.6	4.2
Spire Missouri | Pension Plans | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	43.9	45.1
Spire Missouri | Pension Plans | Derivatives and margin (payable)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(0.8)	(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	265.7	295.3
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	35.2	31.7
Spire Missouri | Pension Plans | Quoted Prices in Active Markets (Level 1) | Equity mutual funds - U.S.
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	0
Spire Missouri | Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. 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) | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	31.7	33.2
Spire Missouri | Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	152.1	183.7
Spire Missouri | Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3.6	4.2
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	43.9	45.1
Spire Missouri | Pension Plans | Quoted Prices in Active Markets (Level 1) | Derivatives and margin (payable)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	(0.8)	(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	83.4	90.6
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 - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	8.4	11.9
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	4.1	5.7
Spire Missouri | Pension Plans | Significant Observable Inputs (Level 2) | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	64.9	68.5
Spire Missouri | Pension Plans | Significant Observable Inputs (Level 2) | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3	4.5
Spire Missouri | Pension Plans | Significant Observable Inputs (Level 2) | U.S. 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) | U.S. municipal
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	3	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) | Derivatives and margin (payable)
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)
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) | 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 - U.S.
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 - 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) | U.S. 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) | U.S. 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) | U.S. 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) | U.S. 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) | Derivatives and margin (payable)
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
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	189.5	174.9	159.7
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	3.5	3.9
Spire Missouri | Postretirement Plans | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	186	171
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	189.5	174.9
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	3.5	3.9
Spire Missouri | Postretirement Plans | Quoted Prices in Active Markets (Level 1) | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	186	171
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 - U.S.
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 - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0	0
Spire Alabama
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	8.8
Spire Alabama | 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
Spire Alabama | Significant Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	8.8
Spire Alabama | 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
Spire Alabama | Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	101.3	97.9	100
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	10.4	3.4
Spire Alabama | Pension Plans | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	37.4	37.5
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	14	28.9
Spire Alabama | Pension Plans | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	24.2	23.2
Spire Alabama | Pension Plans | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	1.8
Spire Alabama | Pension Plans | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	4.7	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	77.4	80.2
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	10.4	3.4
Spire Alabama | Pension Plans | Quoted Prices in Active Markets (Level 1) | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	28.8	28.4
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	14	25.2
Spire Alabama | Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. bond mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	24.2	23.2
Spire Alabama | Pension Plans | Quoted Prices in Active Markets (Level 1) | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	0
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	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	23.9	17.7
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 - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	8.6	9.1
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	0	3.7
Spire Alabama | Pension Plans | Significant Observable Inputs (Level 2) | U.S. 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 Observable Inputs (Level 2) | U.S. government
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	1.8
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	4.7	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 - U.S.
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	0
Spire Alabama | Pension Plans | Significant Unobservable Inputs (Level 3) | U.S. 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) | U.S. government
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) | 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
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	89.6	86.4	$ 82.8
Spire Alabama | Postretirement Plans | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	74.5	71.7
Spire Alabama | Postretirement Plans | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	15.1	14.7
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 - U.S.
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	89.6	86.4
Spire Alabama | Postretirement Plans | Significant Observable Inputs (Level 2) | Equity mutual funds - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value measurements of plan assets	74.5	71.7
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	15.1	14.7
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 - U.S.
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 SEGM_3

INFORMATION BY OPERATING SEGMENT - Schedule of Operating Segment Information (Details) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2018USD ($)operating_segment	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of operating segments | operating_segment									2
Operating Segment Information [Abstract]
Total Operating Revenues	$ 239.2	$ 350.6	$ 813.4	$ 561.8	$ 258.7	$ 323.5	$ 663.4	$ 495.1	$ 1,965	$ 1,740.7	$ 1,537.3
Gas Utility
Natural and propane gas									770.1	570.5	492.2
Other operation and maintenance expenses									455.6	405	377.5
Depreciation and amortization									167	153.5	136.9
Taxes, other than income taxes									152.5	137.8	125.2
Total Gas Utility Operating Expenses									1,545.2	1,266.8	1,131.8
Gas Marketing and other									140.1	152.2	123.2
Total Operating Expenses									1,685.3	1,419	1,255
Operating Income	(19.6)	$ 52.4	$ 141.8	$ 105.1	1.9	$ 50.3	$ 180.4	$ 89.1	279.7	321.7	282.3
Net Economic Earnings									183.7	167.6	149.1
Capital Expenditures									499.4	438.1	293.3
ASSETS
Total Assets	6,843.6				6,546.7				6,843.6	6,546.7	6,064.4
Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									(11.5)	(14.2)	(5.4)
Gas Utility
Natural and propane gas									(72.5)	(75.4)	(47.5)
Other operation and maintenance expenses									(8.5)	(4.1)	(1.8)
Depreciation and amortization									0	0	0
Taxes, other than income taxes									0	0	0
Total Gas Utility Operating Expenses									(81)	(79.5)	(49.3)
Gas Marketing and other									69.5	65.3	43.9
Total Operating Expenses									(11.5)	(14.2)	(5.4)
Operating Income									0	0	0
Net Economic Earnings									0	0	0
Capital Expenditures									0	0	0
ASSETS
Total Assets	(1,566.4)				(1,490.2)				(1,566.4)	(1,490.2)	(1,161.9)
Gas Utility
Operating Segment Information [Abstract]
Total Operating Revenues									1,888	1,660	1,457.2
Gas Utility | Operating Segments
Operating Segment Information [Abstract]
Total Operating Revenues									1,888.4	1,667.9	1,459.4
Gas Utility
Natural and propane gas									842.6	645.9	539.7
Other operation and maintenance expenses									464.1	409.1	379.3
Depreciation and amortization									167	153.5	136.9
Taxes, other than income taxes									152.5	137.8	125.2
Total Gas Utility Operating Expenses									1,626.2	1,346.3	1,181.1
Gas Marketing and other									0	0	0
Total Operating Expenses									1,626.2	1,346.3	1,181.1
Operating Income									262.2	321.6	278.3
Net Economic Earnings									183.1	181.5	160.3
Capital Expenditures									457.7	412.6	291.7
ASSETS
Total Assets	5,606.7				5,551.2				5,606.7	5,551.2	5,184.7
Gas Utility | Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									0.4	7.9	2.2
Gas Marketing
Operating Segment Information [Abstract]
Total Operating Revenues									71.6	79.3	78.5
Gas Marketing | Operating Segments
Operating Segment Information [Abstract]
Total Operating Revenues									71.6	79.3	78.5
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									37.8	74.1	66.7
Total Operating Expenses									37.8	74.1	66.7
Operating Income									33.8	5.2	11.8
Net Economic Earnings									22.9	6.8	6.4
Capital Expenditures									0	0	0
Depreciation and amortization expense									0	0.1	0.1
ASSETS
Total Assets	295.3				246.2				295.3	246.2	205
Gas Marketing | Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									0	0	0
Other
Operating Segment Information [Abstract]
Total Operating Revenues									5.4	1.4	1.6
Other | Operating Segments
Operating Segment Information [Abstract]
Total Operating Revenues									16.5	7.7	4.8
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									32.8	12.8	12.6
Total Operating Expenses									32.8	12.8	12.6
Operating Income									(16.3)	(5.1)	(7.8)
Net Economic Earnings									(22.3)	(20.7)	(17.6)
Capital Expenditures									41.7	25.5	1.6
Depreciation and amortization expense									1.4	0.5	0.5
ASSETS
Total Assets	$ 2,508				$ 2,239.5				2,508	2,239.5	1,836.6
Other | Eliminations
Operating Segment Information [Abstract]
Total Operating Revenues									$ 11.1	$ 6.3	$ 3.2

INFORMATION BY OPERATING SEGM_4

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, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting [Abstract]
Net income	$ (25.9)	$ 25.9	$ 98.2	$ 116	$ (13.3)	$ 21.7	$ 108	$ 45.2	$ 214.2	$ 161.6	$ 144.2
Missouri regulatory adjustments									30.6
Unrealized (gain) loss on energy-related derivatives									(4)	6	(0.1)
Lower of cost or market inventory adjustments									0	0	0.2
Realized gain on economic hedges prior to the sale of the physical commodity									(0.3)	(0.3)	(1.6)
Acquisition, divestiture and restructuring activities									13.6	4	9.2
Income tax effect of adjustments									(10.3)	(3.7)	(2.8)
Effect of the Tax Cuts and Jobs Act									(60.1)	0	0
Net Economic Earnings									$ 183.7	$ 167.6	$ 149.1

REGULATORY MATTERS - Schedule

REGULATORY MATTERS - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Regulatory Assets [Line Items]
Regulatory assets, current	$ 72.8	$ 175.5
Regulatory assets, non current	669.8	791.1
Total Regulatory Assets	742.6	966.6
Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets, current	30.2	42.2
Regulatory assets, non current	364.9	404.7
Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, current	8.2	102.6
Future income taxes due from customers
Regulatory Assets [Line Items]
Regulatory assets, non current	96.3	170.5
Accrued cost of removal
Regulatory Assets [Line Items]
Regulatory assets, non current	133.4	123.3
Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, non current	0	9.9
Energy efficiency
Regulatory Assets [Line Items]
Regulatory assets, non current	32.8	29
Other
Regulatory Assets [Line Items]
Regulatory assets, current	34.4	30.7
Regulatory assets, non current	42.4	53.7
Spire Missouri
Regulatory Assets [Line Items]
Regulatory assets, current	30.7	95.6
Regulatory assets, non current	441.1	557.8
Total Regulatory Assets	471.8	653.4
Spire Missouri | Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets, current	21.9	34.9
Regulatory assets, non current	292.5	322.7
Spire Missouri | Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, current	1	57.4
Spire Missouri | Future income taxes due from customers
Regulatory Assets [Line Items]
Regulatory assets, non current	94.4	170.5
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	0	9.9
Spire Missouri | Energy efficiency
Regulatory Assets [Line Items]
Regulatory assets, non current	32.8	29
Spire Missouri | Other
Regulatory Assets [Line Items]
Regulatory assets, current	7.8	3.3
Regulatory assets, non current	21.4	25.7
Spire Alabama
Regulatory Assets [Line Items]
Regulatory assets, current	26.2	64.6
Regulatory assets, non current	201.5	197
Total Regulatory Assets	227.7	261.6
Spire Alabama | Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets, current	7.3	7.2
Regulatory assets, non current	64.8	72.6
Spire Alabama | Unamortized purchased gas adjustments
Regulatory Assets [Line Items]
Regulatory assets, current	6.4	45.2
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	133.4	123.3
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	12.5	12.2
Regulatory assets, non current	$ 3.3	$ 1.1

REGULATORY MATTERS - Schedule o

REGULATORY MATTERS - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	$ 35.7	$ 22.6
Total Noncurrent Regulatory Liabilities	354.6	157.2
Total Regulatory Liabilities	390.3	179.8
RSE adjustment
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	1.4
Refundable negative salvage
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	5.2	8.2
Total Noncurrent Regulatory Liabilities	0	4.1
Unamortized purchased gas adjustments
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	2.9	1
Weather Normalization Adjustment Rider
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	4.7	1.9
Other
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	27.6	12
Total Noncurrent Regulatory Liabilities	80.2	35.2
Unamortized Investment Tax Credits [Member]
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	178.3	0
Postretirement Benefit Costs
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	27.8	32.2
Accrued cost of removal
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	63.6	83.8
Spire Missouri
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	16.7	2.7
Total Noncurrent Regulatory Liabilities	274.9	81.2
Total Regulatory Liabilities	291.6	83.9
Spire Missouri | RSE adjustment
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Spire Missouri | Refundable negative salvage
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Total Noncurrent Regulatory Liabilities	0	0
Spire Missouri | Unamortized purchased gas adjustments
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	1.9	0
Spire Missouri | Weather Normalization Adjustment Rider
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	4.7	1.9
Spire Missouri | Other
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	14.8	2.7
Total Noncurrent Regulatory Liabilities	69.3	24.8
Spire Missouri | Unamortized Investment Tax Credits [Member]
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	161.1	0
Spire Missouri | 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	39.8	54.5
Spire Alabama
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	7.6	12
Total Noncurrent Regulatory Liabilities	31.3	39.6
Total Regulatory Liabilities	38.9	51.6
Spire Alabama | RSE adjustment
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	1.4
Spire Alabama | Refundable negative salvage
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	5.2	8.2
Total Noncurrent Regulatory Liabilities	0	4.1
Spire Alabama | Unamortized purchased gas adjustments
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	0	0
Spire Alabama | Weather Normalization Adjustment Rider
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	0	0
Spire Alabama | Other
Regulatory Liabilities [Line Items]
Total Current Regulatory Liabilities	2.4	2.4
Total Noncurrent Regulatory Liabilities	3.5	3.3
Spire Alabama | Unamortized Investment Tax Credits [Member]
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	0	0
Spire Alabama | Postretirement Benefit Costs
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	27.8	32.2
Spire Alabama | Accrued cost of removal
Regulatory Liabilities [Line Items]
Total Noncurrent Regulatory Liabilities	$ 0	$ 0

REGULATORY MATTERS - Schedule_2

REGULATORY MATTERS - Schedule of Regulatory Assets Not Earnings a Return (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	$ 259.8	$ 380.3
Future income taxes due from customers
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	148.4	170.5
Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	96.3	198.5
Other
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	15.1	11.3
Spire Missouri
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	257.9	380.3
Spire Missouri | Future income taxes due from customers
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	148.4	170.5
Spire Missouri | Pension and postretirement benefit costs
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	94.4	198.5
Spire Missouri | Other
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	$ 15.1	$ 11.3

REGULATORY MATTERS - Additional

REGULATORY MATTERS - Additional Information (Details)	12 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
Recovery period	20 years
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided	15 years

REGULATORY MATTERS - Spire Miss

REGULATORY MATTERS - Spire Missouri (Details)	Sep. 28, 2018USD ($)	Jun. 07, 2018USD ($)	Mar. 07, 2018USD ($)$ / shares	Sep. 15, 2017USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2018USD ($)	Sep. 30, 2018USD ($)operating_segment	Sep. 20, 2018USD ($)	Apr. 19, 2018USD ($)	Sep. 30, 2017USD ($)	Apr. 11, 2017USD ($)
Public Utilities, General Disclosures [Line Items]
Customer Share					100.00%		75.00%			85.00%
Decreases resulting from TCJA's federal rate reduction			$ 33,000,000
Regulatory assets							$ 742,600,000			$ 966,600,000
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided							15 years
Regulatory costs							$ 30,600,000
Spire Missouri
Public Utilities, General Disclosures [Line Items]
Number of PGA Discretionary Changes | operating_segment							3
Months between PGA Discretionary Changes							2 months
Regulatory assets							$ 471,800,000			$ 653,400,000
Regulatory preferred stock and debt securities issuance, amount authorized							$ 500,000,000
Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Customer Share							25.00%
Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Customer Share							25.00%
MoPSC
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), annualized revenue				$ 200,000
MoPSC | Spire Missouri
Public Utilities, General Disclosures [Line Items]
Cost savings retention percentage							10.00%
Maximum amount of cost savings allowable							$ 3
Regulatory preferred stock and debt securities issuance, amount authorized								$ 500,000,000
MoPSC | Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount			18,000,000
MoPSC | Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount			15,200,000
Infrastructure System Replacement Surcharge
Public Utilities, General Disclosures [Line Items]
Recommended rate increase (decrease) amount					$ 3,000,000
Infrastructure System Replacement Surcharge | Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount	$ 2,600,000
Approved rate increase (decrease), annualized revenue					4,500,000
Requested rate increase		$ 4,800,000
Infrastructure System Replacement Surcharge | Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount	$ 5,400,000
Approved rate increase (decrease), annualized revenue					$ 3,200,000
Requested rate increase		$ 7,100,000
Infrastructure System Replacement Surcharge | MoPSC
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount			0
Incentive compensation costs			6,900,000
Incentive compensation costs, assets			1,800,000
Rate case expenses			900,000
Regulatory costs							$ 38,400,000
After-tax rate reduction to net income			$ 23,600,000
After-tax rate reduction to earnings per share | $ / shares			$ 0.49
Infrastructure System Replacement Surcharge | MoPSC | Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount			$ 32,600,000
Approved rate increase (decrease), annualized revenue			14,600,000
Infrastructure System Replacement Surcharge | MoPSC | Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount			16,400,000
Approved rate increase (decrease), annualized revenue			1,200,000
Pension Cost | Infrastructure System Replacement Surcharge | MoPSC
Public Utilities, General Disclosures [Line Items]
Regulatory assets recovery			(28,800,000)
Regulatory costs			30,600,000
Pension Cost | Infrastructure System Replacement Surcharge | MoPSC | Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Regulatory assets			29,000,000								$ 15,500,000
Pension Cost | Infrastructure System Replacement Surcharge | MoPSC | Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Regulatory assets			5,500,000								9,900,000
Postretirement Benefit Costs | Infrastructure System Replacement Surcharge | MoPSC | Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Regulatory assets			$ 8,600,000						$ 8,600,000		$ 9,500,000
Pension and Other Postretirement Benefits | Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided						8 years	8 years
Amortization of assets						$ 173,000,000	$ 173,000,000
Pension and Other Postretirement Benefits | Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Amortization of assets						$ 26,200,000	$ 26,200,000

REGULATORY MATTERS - Off-system

REGULATORY MATTERS - Off-system Sales (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Off-System Sales [Line Items]
Customer Share	75.00%	85.00%	100.00%
Company Share		15.00%
Spire Missouri East
Off-System Sales [Line Items]
Customer Share	25.00%
Spire Missouri West
Off-System Sales [Line Items]
Customer Share	25.00%
First $2.0 of pre-tax income | Spire Missouri East
Off-System Sales [Line Items]
Pre-tax Income	$ 2
Customer Share	85.00%
Company Share	15.00%
Next $2.0 of pre-tax income | Spire Missouri East
Off-System Sales [Line Items]
Pre-tax Income	$ 2
Customer Share	80.00%
Company Share	20.00%
Next $2.0 of pre-tax income | Spire Missouri East
Off-System Sales [Line Items]
Pre-tax Income	$ 2
Customer Share	75.00%
Company Share	25.00%
Amounts of pre-tax income exceeding $6.0 | Spire Missouri East
Off-System Sales [Line Items]
Pre-tax Income	$ 6
Customer Share	70.00%
Company Share	30.00%
First $1.2 of pre-tax income | Spire Missouri West
Off-System Sales [Line Items]
Pre-tax Income	$ 1.2
Customer Share	85.00%
Company Share	15.00%
Next $1.2 of pre-tax income | Spire Missouri West
Off-System Sales [Line Items]
Pre-tax Income	$ 1.2
Customer Share	80.00%
Company Share	20.00%
Next $1.2 of pre-tax income | Spire Missouri West
Off-System Sales [Line Items]
Pre-tax Income	$ 1.2
Customer Share	75.00%
Company Share	25.00%
Amounts of pre-tax income exceeding $3.6 | Spire Missouri West
Off-System Sales [Line Items]
Pre-tax Income	$ 3.6
Customer Share	70.00%
Company Share	30.00%

REGULATORY MATTERS - Spire Alab

REGULATORY MATTERS - Spire Alabama (Details) - USD ($) $ in Millions	Oct. 01, 2018	Feb. 01, 2018	Nov. 30, 2017	Sep. 30, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 01, 2014	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Oct. 02, 2018
Public Utilities, General Disclosures [Line Items]
Regulatory costs								$ 30.6
Amounts returned to customers				$ 22.6				35.7	$ 22.6
Amount to be refunded				179.8				390.3	179.8
Spire Alabama
Public Utilities, General Disclosures [Line Items]
Regulatory costs		$ 12.8
Amounts returned to customers				12				7.6	12
Amount to be refunded				51.6				$ 38.9	51.6
Potential Performance-Based Adjustment, Percent								0.05%
APSC | Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity	10.40%						10.80%
Maximum return on equity, percentage of prior year revenues								4.00%
Approved rate increase (decrease) amount				2.7	$ 0	$ 0		$ 9.7	10.7	$ 7.8
Requested rate increase			$ 8.5
Rate increase (decrease), margin of index range								1.75%
Amount to be refunded								$ 5.2
Line of credit facility borrowing capacity								200
Principal amount outstanding								25
ESR | APSC
Public Utilities, General Disclosures [Line Items]
Extraordinary O&M expenses in excess of								1
Single force majeure								0.3
Multiple force majeures								0.4
Revenue variances								$ 0.4
ESR term								9 years
Underfunded ESR balances amortization term								5 years
ESR annual limitation								$ 0.7
Minimum | APSC | Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity	10.15%						10.50%
Equity limitation as percent of capitalization							55.50%
Maximum | APSC | Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity	10.65%						10.95%
Equity limitation as percent of capitalization							56.50%
Subsequent Event | APSC | Spire Alabama
Public Utilities, General Disclosures [Line Items]
Regulatory preferred stock and debt securities issuance, amount authorized											$ 90
Amount subject to refund
Public Utilities, General Disclosures [Line Items]
Amounts returned to customers				8.2				5.2	8.2
Amount subject to refund | Spire Alabama
Public Utilities, General Disclosures [Line Items]
Amounts returned to customers				8.2				5.2	8.2
Amount subject to refund | APSC | Spire Alabama
Public Utilities, General Disclosures [Line Items]
Amounts returned to customers				$ 6.3				$ 7.2	$ 6.3	$ 8.3

REGULATORY MATTERS - Spire (Det

REGULATORY MATTERS - Spire (Details) - USD ($) $ in Thousands	Feb. 01, 2018	Sep. 15, 2017	Dec. 31, 2015	Sep. 30, 2018
Public Utilities, General Disclosures [Line Items]
Regulatory costs				$ 30,600
Spire Gulf
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity				10.70%
Rate increase (decrease), margin of index range				1.50%
Pro-rate rating for equity content				75.00%
Revenue variances				$ 100
Single force majeure				100
Multiple force majeures				$ 150
Recovery percentage of incurred costs				90.00%
Spire
Public Utilities, General Disclosures [Line Items]
Regulatory costs	$ 1,900
Spire Mississippi
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity				9.34%
Excess of allowed return on equity				1.00%
Return on equity shortfall				75.00%
Excess return on equity				50.00%
Recovery period			3 years
APSC | Spire
Public Utilities, General Disclosures [Line Items]
Line of credit facility borrowing capacity				$ 50,000
Principal amount outstanding				$ 25,000
MoPSC
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), annualized revenue		$ 200
Minimum | Spire Gulf
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity				10.45%
Maximum | Spire Gulf
Public Utilities, General Disclosures [Line Items]
Approved return rate on equity				10.95%

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Commitments (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	$ 1,240.9
Outstanding mortgage loans incurred in connection with various real estate ventures with general partners	1.3
Spire Missouri
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	572.4
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	$ 286.5

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Loss Contingencies [Line Items]
Aggregate rental expense	$ 10	$ 9.7	$ 11.9
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum rental commitments - in fiscal year 2019	9.7
Minimum rental commitments - due in fiscal year 2020	7.8
Minimum rental commitments - due in fiscal year 2021	6.7
Minimum rental commitments - due in fiscal year 2022	6.5
Minimum rental commitments - due in fiscal year 2023	6.5
Minimum rental commitments - due later	41.3
Minimum rental commitments - total	78.5
Sublease rentals	2.1	2.1	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
Spire Missouri
Loss Contingencies [Line Items]
Aggregate rental expense	3.6	4.8	4.3
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum rental commitments - in fiscal year 2019	1.3
Minimum rental commitments - due in fiscal year 2020	0.6
Minimum rental commitments - due in fiscal year 2021	0.3
Minimum rental commitments - due in fiscal year 2022	0.1
Minimum rental commitments - due in fiscal year 2023	0
Minimum rental commitments - due later	0
Minimum rental commitments - total	2.3
Spire Alabama
Loss Contingencies [Line Items]
Aggregate rental expense	4.7	4.6	3.7
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum rental commitments - in fiscal year 2019	4.1
Minimum rental commitments - due in fiscal year 2020	2.9
Minimum rental commitments - due in fiscal year 2021	2.1
Minimum rental commitments - due in fiscal year 2022	2.1
Minimum rental commitments - due in fiscal year 2023	2.1
Minimum rental commitments - due later	0.7
Minimum rental commitments - total	14
Sublease rentals	2.1	$ 2.1	$ 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 CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Contingencies (Details)	12 Months Ended
	Sep. 30, 2018plaintifflawsuitsite	Sep. 30, 2013site
Site Contingency [Line Items]
Number of lawsuits | lawsuit	14
Number of plaintiffs | plaintiff	1,600
Pending Litigation
Site Contingency [Line Items]
Number of lawsuits pending | plaintiff	13
Spire Missouri
Site Contingency [Line Items]
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

INTERIM FINANCIAL INFORMATION_3

INTERIM FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Quarterly Financial Information [Line Items]
Total Operating Revenues	$ 239.2	$ 350.6	$ 813.4	$ 561.8	$ 258.7	$ 323.5	$ 663.4	$ 495.1	$ 1,965	$ 1,740.7	$ 1,537.3
Operating Income (Loss)	(19.6)	52.4	141.8	105.1	1.9	50.3	180.4	89.1	279.7	321.7	282.3
Net Income (Loss)	$ (25.9)	$ 25.9	$ 98.2	$ 116	$ (13.3)	$ 21.7	$ 108	$ 45.2	$ 214.2	$ 161.6	$ 144.2
Basic Earnings Per Share of Common Stock (in dollars per share)	$ (0.51)	$ 0.52	$ 2.03	$ 2.40	$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ 4.35	$ 3.44	$ 3.26
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ (0.51)	$ 0.52	$ 2.03	$ 2.39	$ (0.28)	$ 0.45	$ 2.36	$ 0.99	$ 4.33	$ 3.43	$ 3.24
Spire Missouri
Quarterly Financial Information [Line Items]
Total Operating Revenues	$ 144.6	$ 215.5	$ 533.2	$ 392.3	$ 162.6	$ 198.5	$ 447.2	$ 363.6	$ 1,285.6	$ 1,171.9	$ 1,087.5
Operating Income (Loss)	(6.6)	21	52.1	74.8	11.7	30.5	90.2	64.5	141.3	196.9	186.9
Net Income (Loss)	(10)	11.5	38.4	89.4	2.5	15.5	57	38	129.3	113	105.9
Spire Alabama
Quarterly Financial Information [Line Items]
Total Operating Revenues	61.3	100.3	218.3	120.8	64.5	90.5	158.8	86.7	500.7	400.5	368.5
Operating Income (Loss)	(10.9)	12.3	78.2	19	(8.4)	15.5	78.9	19.8	98.6	105.8	91.5
Net Income (Loss)	$ (11)	$ 6.3	$ 55.6	$ (49.6)	$ (7.2)	$ 7.4	$ 47.6	$ 10.3	$ 1.3	$ 58.1	$ 53.2