Net earnings (loss) per unitholders' interest (Details)	12 Months Ended
	Jul. 31, 2022 USD ($) $ / shares shares	Jul. 31, 2021 USD ($) $ / shares shares	Jul. 31, 2020 USD ($) $ / shares shares
Earnings Distribution Allocation [Line Items]
Net earnings attributable to Ferrellgas Partners, L.P.	$ 147,993,000	$ (68,411,000)	$ (82,499,000)
Less: General partner's interest in net earnings (loss)	1,480,000	(684,000)	(825,000)
Value of dilutive securities	0
Undistributed net loss attributable to Class A unitholders	$ (18,770,000)	(91,751,000)	(81,674,000)
Allocation of earnings to Class B units relative to allocation to Class A units	6
Preferred Units
Earnings Distribution Allocation [Line Items]
Less: Distributions to preferred unitholders	$ 65,287,000	24,024,000
Class A Limited Partner Units
Earnings Distribution Allocation [Line Items]
Undistributed net loss attributable to Class A unitholders	$ (18,770,000)	$ (91,751,000)	$ (81,674,000)
Weighted Average Number of Shares Outstanding, Basic | shares	4,857,600	4,857,600	4,857,600
Weighted Average Number of Shares Outstanding, Diluted | shares	4,857,600	4,857,600	4,857,600
Basic and diluted net earnings (loss) per limited partner unit | $ / shares	$ (3.86)	$ (18.89)	$ (16.81)
Class B Limited Partner Units
Earnings Distribution Allocation [Line Items]
Less: Distributions to preferred unitholders	$ 99,996,000