Derivative Instruments and Hedging Activities - Effect on Comprehensive Income and Change in FV (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	$ 36,957	$ (11,212)	$ 42,724	$ (24,839)
Amount of gain (loss) reclassified from AOCI into income	8,441	(8,766)	6,291	(16,245)
Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	36,957	(11,212)	42,724	(24,839)
Cost of Sales [Member] | Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	8,441	(8,766)	6,291	(16,245)
Ferrellgas, L.P. [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	36,957	(11,212)	42,724
Amount of gain (loss) reclassified from AOCI into income	8,441	(8,766)	6,291
Ferrellgas, L.P. [Member] | Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in AOCI on derivative	36,957	(11,212)	42,724	(24,839)
Amount of gain (loss) reclassified from AOCI into income				(16,245)
Ferrellgas, L.P. [Member] | Cost of Sales [Member] | Commodity Derivatives Propane [Member]
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	$ 8,441	$ (8,766)	$ 6,291	$ (16,245)