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Revenue from contracts with customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Jul. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 300,894	$ 293,214
Contract assets and liabilities
Accounts receivable	132,570		$ 108,483
Contract assets	3,699		7,079
Contract liabilities
Deferred revenue	52,220		42,911
Deferred revenue recognized	$ 11,400
Maximum [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-11-01
Contract liabilities
Remaining performance obligation recognition period	1 year
Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 300,894	293,214
Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues	174,645	180,417
Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues	102,612	82,704
Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,792	10,264
Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	19,845	19,829
Ferrellgas, L.P. [Member]
Disaggregation of Revenue [Line Items]
Revenues	300,894	293,214
Contract assets and liabilities
Accounts receivable	132,570		108,483
Contract assets	3,699		7,079
Contract liabilities
Deferred revenue	52,220		$ 42,911
Deferred revenue recognized	$ 11,400
Ferrellgas, L.P. [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-11-01
Contract liabilities
Remaining performance obligation recognition period	1 year
Ferrellgas, L.P. [Member] \| Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 300,894	293,214
Ferrellgas, L.P. [Member] \| Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues	174,645	180,417
Ferrellgas, L.P. [Member] \| Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues	102,612	82,704
Ferrellgas, L.P. [Member] \| Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,792	10,264
Ferrellgas, L.P. [Member] \| Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 19,845	$ 19,829