Revenue from contracts with customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019	Jul. 31, 2019
Disaggregation of Revenue [Line Items]
Accounts receivable collection period			30 days
Residential customer, annual cost spread period			12 months
Rental income recognition period			1 year
Revenues	$ 510,833	$ 573,377	$ 804,047	$ 925,686
Contract assets and liabilities
Accounts receivable	171,765		171,765		$ 96,450
Contract assets	13,144		13,144		13,609
Contract liabilities
Deferred revenue	$ 37,351		37,351		31,974
Deferred revenue recognized			$ 18,400
Maximum [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-02-01
Contract liabilities
Remaining performance obligation recognition period	1 year		1 year
Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 510,833		$ 804,047
Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues	374,069		554,486
Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues	105,055		187,759
Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	6,123		16,387
Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	25,586	23,265	$ 45,415	40,608
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues		573,377		925,686
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues		415,827		633,591
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues		115,392		209,336
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues		18,893		42,151
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other Revenues
Disaggregation of Revenue [Line Items]
Revenues		23,265		40,608
Ferrellgas, L.P. [Member]
Disaggregation of Revenue [Line Items]
Accounts receivable collection period			30 days
Residential customer, annual cost spread period			12 months
Rental income recognition period			1 year
Revenues	510,833	573,377	$ 804,047	925,686
Contract assets and liabilities
Accounts receivable	171,765		171,765		96,450
Contract assets	13,144		13,144		13,609
Contract liabilities
Deferred revenue	$ 37,351		37,351		$ 31,974
Deferred revenue recognized			$ 18,400
Ferrellgas, L.P. [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-02-01
Contract liabilities
Remaining performance obligation recognition period	1 year		1 year
Ferrellgas, L.P. [Member] | Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 510,833		$ 804,047
Ferrellgas, L.P. [Member] | Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues	374,069		554,486
Ferrellgas, L.P. [Member] | Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues	105,055		187,759
Ferrellgas, L.P. [Member] | Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	6,123		16,387
Ferrellgas, L.P. [Member] | Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 25,586	23,265	$ 45,415	40,608
Ferrellgas, L.P. [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Disaggregation of Revenue [Line Items]
Revenues		573,377		925,686
Ferrellgas, L.P. [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues		573,377		925,686
Ferrellgas, L.P. [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues		415,827		633,591
Ferrellgas, L.P. [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues		115,392		209,336
Ferrellgas, L.P. [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues		18,893		42,151
Ferrellgas, L.P. [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other Revenues
Disaggregation of Revenue [Line Items]
Revenues		$ 23,265		$ 40,608