Preferred units - Issuance (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Jul. 31, 2022	Jul. 31, 2021
Temporary Equity [Line Items]
Preferred units issued (in shares)	700,000
Preferred Units aggregate initial liquidation preference	$ 700.0
Purchase price per Preferred Units	$ 1,000
Purchase price discount	3.00%
Aggregate purchase price	$ 679.0
Senior preferred units, units outstanding	700,000	700,000
Net proceeds from the issuance and sale of the Preferred Units	$ 651.3
Ferrellgas, L.P. [Member]
Temporary Equity [Line Items]
Senior preferred units, units outstanding	700,000	700,000