Fair Value Measurements - Assets and Liabilities (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jan. 31, 2019	Jul. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	$ 5,848	$ 22,470
Commodity derivatives propane swap liabilities	(15,148)	(1,910)
Ferrellgas, L.P. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	5,848	22,470
Commodity derivatives propane swap liabilities	(15,148)	(1,910)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	0	0
Commodity derivatives propane swap liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Ferrellgas, L.P. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	0	0
Commodity derivatives propane swap liabilities	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	5,848	22,470
Commodity derivatives propane swap liabilities	(15,148)	(1,910)
Level 2 [Member] | Ferrellgas, L.P. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	5,848	22,470
Commodity derivatives propane swap liabilities	(15,148)	(1,910)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	0	0
Commodity derivatives propane swap liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Ferrellgas, L.P. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives propane swap assets	0	0
Commodity derivatives propane swap liabilities	$ 0	$ 0