Revenue from contracts with customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Jul. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 553,560	$ 510,833	$ 854,454	$ 804,047
Contract assets and liabilities
Accounts receivable	214,288		214,288		$ 108,483
Contract assets	9,647		9,647		7,079
Contract liabilities
Deferred revenue	$ 44,801		44,801		42,911
Deferred revenue recognized			$ 24,700
Maximum [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-02-01
Contract liabilities
Remaining performance obligation recognition period	1 year		1 year
Propane And Related Equipment [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 553,560	510,833	$ 854,454	804,047
Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues	378,350	374,069	552,995	554,486
Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues	138,730	105,055	241,342	187,759
Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	11,354	6,123	15,146	16,387
Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	25,126	25,586	44,971	45,415
Ferrellgas, L.P. [Member]
Disaggregation of Revenue [Line Items]
Revenues	553,560	510,833	854,454	804,047
Contract assets and liabilities
Accounts receivable	214,288		214,288		108,483
Contract assets	9,647		9,647		7,079
Contract liabilities
Deferred revenue	$ 44,801		44,801		$ 42,911
Deferred revenue recognized			$ 24,700
Ferrellgas, L.P. [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-02-01
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	$ 553,560	510,833	$ 854,454	804,047
Ferrellgas, L.P. [Member] | Retail Sales To End Users [Member]
Disaggregation of Revenue [Line Items]
Revenues	378,350	374,069	552,995	554,486
Ferrellgas, L.P. [Member] | Wholesale Sales To Resellers [Member]
Disaggregation of Revenue [Line Items]
Revenues	138,730	105,055	241,342	187,759
Ferrellgas, L.P. [Member] | Other Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	11,354	6,123	15,146	16,387
Ferrellgas, L.P. [Member] | Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 25,126	$ 25,586	$ 44,971	$ 45,415