Acquisitions, dispositions and other significant transactions - Loss on sales (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	$ 10,968	$ 187,399	$ 14,457
Ferrellgas, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	10,968	187,399	14,457
Propane And Related Equipment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	0	15,194	0
Propane And Related Equipment [Member] | Ferrellgas, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	0	15,194	0
Midstream Operations [Member] | Trucking Water Disposal And Terminal Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	2,679	120,240	0
Midstream Operations [Member] | Trucking Water Disposal And Terminal Assets [Member] | Ferrellgas, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	2,679	120,240	0
Midstream Operations [Member] | Rail cars [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	0	36,762	0
Midstream Operations [Member] | Rail cars [Member] | Ferrellgas, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	0	36,762	0
Bridger Environmental LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	0	4,002	0
Bridger Environmental LLC [Member] | Ferrellgas, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	0	4,002	0
Other Disposals Not Individually Significant [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	8,289	11,201	14,457
Other Disposals Not Individually Significant [Member] | Ferrellgas, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on asset sales and disposals	$ 8,289	$ 11,201	$ 14,457