Debt - Security (Details) - USD ($) $ in Millions	Jan. 31, 2021	Jul. 31, 2020
Debt Instrument [Line Items]
Letters of credit outstanding	$ 138.8	$ 126.0
Cash pledged as collateral for letters of credit	91.5	78.2
Accounts Receivable Securitization Facility [Member]
Debt Instrument [Line Items]
Letters of credit outstanding	50.0	50.0
Letter of Credit [Member]
Debt Instrument [Line Items]
Cash pledged as collateral for letters of credit	91.5	78.2
Ferrellgas, L.P. [Member]
Debt Instrument [Line Items]
Letters of credit outstanding	138.8	126.0
Cash pledged as collateral for letters of credit	91.5	78.2
Ferrellgas, L.P. [Member] | Accounts Receivable Securitization Facility [Member]
Debt Instrument [Line Items]
Letters of credit outstanding	50.0	50.0
Ferrellgas, L.P. [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Cash pledged as collateral for letters of credit	$ 91.5	$ 78.2