Debt Debt (Consolidated Interest Coverage Ratio) (Details)	3 Months Ended	12 Months Ended
	Apr. 30, 2017	Jul. 31, 2016	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017
Debt Instrument, Covenant Description	43.9
current consolidated interest coverage ratio	229.00%
Debt Instrument, Covenant Compliance	340.2	8.1
Minimum [Member]
required consolidated interest coverage ratio	250.00%		250.00%	250.00%	250.00%	250.00%	250.00%
Maximum [Member]
required consolidated interest coverage ratio	175.00%		250.00%	175.00%	175.00%	175.00%	175.00%
Ferrellgas, L.P. [Member]
Debt Instrument, Covenant Description	43.9
current consolidated interest coverage ratio	229.00%
Debt Instrument, Covenant Compliance	340.2	8.1
Ferrellgas, L.P. [Member] | Minimum [Member]
required consolidated interest coverage ratio	250.00%		250.00%	250.00%	250.00%	250.00%	250.00%
Ferrellgas, L.P. [Member] | Maximum [Member]
required consolidated interest coverage ratio	175.00%		250.00%	175.00%	175.00%	175.00%	175.00%
Interest Coverage Covenant [Member]
Debt Instrument, Covenant Description	61.5
Debt Instrument, Covenant Compliance	35.2
Interest Coverage Covenant [Member] | Ferrellgas, L.P. [Member]
Debt Instrument, Covenant Description	61.5
Debt Instrument, Covenant Compliance	35.2