Derivative Instruments and Hedging Activities - Effect on Comprehensive Income and Change in FV (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	$ 5,767	$ (13,627)
Amount of gain (loss) reclassified from AOCI into income	(2,150)	(7,479)
Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	5,767	(13,627)
Cost of Sales [Member] | Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	(2,150)	(7,479)
Ferrellgas, L.P. [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	5,767	(13,627)
Amount of gain (loss) reclassified from AOCI into income	(2,150)	(7,479)
Ferrellgas, L.P. [Member] | Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	5,767	(13,627)
Ferrellgas, L.P. [Member] | Propane [Member] | Cost of Sales [Member] | Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	$ (2,150)	$ (7,479)