Acquisitions, dispositions and other significant transactions - Fair Value Allocation (Details) - USD ($) $ in Thousands	12 Months Ended
Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill	$ 247,195	$ 247,195
Propane and related equipment sales [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Working capital		31	$ 758
Customer tanks, buildings, land, salt water disposal wells, and other	6,598	11,560	10,022
Goodwill	247,195	247,195	246,098
Aggregate fair value of transactions	11,170	15,201	20,567
Propane and related equipment sales [Member] \| Customer Lists [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Finite-lived Intangible Assets Acquired	738	1,272	7,758
Propane and related equipment sales [Member] \| Non-Compete Agreements [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Finite-lived Intangible Assets Acquired	3,834	928	2,029
Series of Individually Immaterial Business Acquisitions [Member] \| Propane and related equipment sales [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill		1,410
Ferrellgas, L.P. [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill	247,195	247,195
Ferrellgas, L.P. [Member] \| Propane and related equipment sales [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Working capital		31	758
Customer tanks, buildings, land, salt water disposal wells, and other	6,598	11,560	10,022
Goodwill	247,195	247,195	246,098
Aggregate fair value of transactions	11,170	15,201	20,567
Ferrellgas, L.P. [Member] \| Propane and related equipment sales [Member] \| Customer Lists [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Finite-lived Intangible Assets Acquired	738	1,272	7,758
Ferrellgas, L.P. [Member] \| Propane and related equipment sales [Member] \| Non-Compete Agreements [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Finite-lived Intangible Assets Acquired	$ 3,834	928	$ 2,029
Ferrellgas, L.P. [Member] \| Series of Individually Immaterial Business Acquisitions [Member] \| Propane and related equipment sales [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets [Abstract]
Goodwill		$ 1,410

Amount of assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Amount recognized as of the acquisition date for the assets, including goodwill, in excess of (less than) the aggregate liabilities assumed, less the noncontrolling interest in the acquiree.

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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