Accounting Policies

No definition available.

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- Definition

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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- Definition

Amount of increase (decrease) from measurement period adjustment of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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Amount of cash restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
	Mar. 31, 2026	Jun. 30, 2026	Mar. 31, 2026	Sep. 30, 2025	Jun. 30, 2025
Accounting Policies [Line Items]
Goodwill		$ 1,895.2		$ 1,171.6	$ 1,171.6
Restricted cash		38.3		35.5	35.0
Spire Missouri [Member]
Accounting Policies [Line Items]
Goodwill		210.2		210.2	$ 210.2
Southeast Utilities [Member]
Accounting Policies [Line Items]
Goodwill		18.1		$ 961.4
Spire Tennessee [Member]
Accounting Policies [Line Items]
Goodwill		741.7
Goodwill purchase accounting for the acquisition		3.8
Spire Mississippi [Member]
Accounting Policies [Line Items]
Goodwill impairment			$ 3.9
Piedmont Tennessee Transaction [Member]
Accounting Policies [Line Items]
Goodwill	$ 741.7	741.7	741.7
Goodwill purchase accounting for the acquisition		3.8
Payments to acquire businesses, gross	$ 2,500.0		$ 2,500.0
Piedmont Tennessee Transaction [Member] \| Spire Tennessee [Member]
Accounting Policies [Line Items]
Goodwill		$ 737.9