Debt Debt (Components of Long-Term Debt) (Details)	3 Months Ended
	Oct. 31, 2017 USD ($)
Fixed Rate, 8.625%, Due 2020 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.625%
Debt maturity year	2020
Fixed Rate, 8.625%, Due 2020 [Member] | Ferrellgas, L.P. [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.625%
Debt maturity year	2020
Maximum [Member] | Fixed Rate, 8.625%, Due 2020 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Face Amount	$ 357,000,000.0
Maximum [Member] | Fixed Rate, 8.625%, Due 2020 [Member] | Ferrellgas, L.P. [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Face Amount	$ 357,000,000.0