Guarantor financial information - Balance Sheets (Details) - USD ($) $ in Thousands	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Jul. 31, 2019
Current assets:
Cash and cash equivalents	$ 299,527	$ 333,761	$ 29,805	$ 11,054
Accounts and notes receivable, net	119,488	101,438
Inventories	78,980	72,664
Prepaid expenses and other current assets	40,088	35,944
Total current assets	538,083	543,807
Property, plant and equipment, net	592,132	591,042
Goodwill, net	246,946	247,195
Intangible assets, net	101,812	104,049
Operating lease, right-of-use assets	100,349	107,349
Other assets, net	73,522	74,748
Total assets	1,652,844	1,668,190
Current liabilities:
Accounts payable	44,641	33,944
Current portion of long-term debt	859,095	859,095
Current operating lease liabilities	28,280	29,345
Other current liabilities	186,938	167,466
Total current liabilities	1,118,954	1,089,850
Long-term debt	1,647,106	1,646,396
Operating lease liabilities	83,337	89,022
Other liabilities	49,543	51,190
Contingencies and commitments
Partners' capital (deficit)
Accumulated other comprehensive income (loss)	5,534	(2,303)
Total Ferrellgas Partners, L.P. partners' deficit	(1,237,566)	(1,200,042)
Total liabilities and partners' capital (deficit)	1,652,844	1,668,190
Ferrellgas, L.P. [Member]
Current assets:
Cash and cash equivalents	299,522	333,755	29,733	11,046
Accounts and notes receivable, net	119,488	101,438
Inventories	78,980	72,664
Prepaid expenses and other current assets	40,044	35,897
Total current assets	538,034	543,754
Property, plant and equipment, net	592,132	591,042
Goodwill, net	246,946	247,195
Intangible assets, net	101,812	104,049
Operating lease, right-of-use assets	100,349	107,349
Other assets, net	73,522	74,748
Total assets	1,652,795	1,668,137
Current liabilities:
Accounts payable	44,641	33,944
Current portion of long-term debt	502,095	502,095
Current operating lease liabilities	28,280	29,345
Other current liabilities	159,910	148,136
Total current liabilities	734,926	713,520
Long-term debt	1,647,106	1,646,396
Operating lease liabilities	83,337	89,022
Other liabilities	49,543	51,190
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(867,721)	(829,678)
Accumulated other comprehensive income (loss)	5,604	(2,313)
Total Ferrellgas Partners, L.P. partners' deficit	(862,117)	(831,991)
Total liabilities and partners' capital (deficit)	1,652,795	1,668,137
Ferrellgas, L.P. [Member] | Reportable Legal Entities [Member] | Parent Company [Member]
Current assets:
Cash and cash equivalents	296,890	332,244	29,732	11,045
Accounts and notes receivable, net	15,547	11,879
Intercompany Receivables, Current	87,191	69,980
Inventories	78,980	72,664
Prepaid expenses and other current assets	40,044	35,897
Total current assets	518,652	522,664
Property, plant and equipment, net	592,132	591,042
Goodwill, net	246,946	247,195
Intangible assets, net	101,812	104,049
Investment in Ferrellgas, L.P.	37,821	37,662
Operating lease, right-of-use assets	100,349	107,349
Other assets, net	71,029	72,137
Total assets	1,668,741	1,682,098
Current liabilities:
Accounts payable	44,641	33,944
Current portion of long-term debt	502,095	502,095
Current operating lease liabilities	28,280	29,345
Other current liabilities	175,856	162,097
Total current liabilities	750,872	727,481
Long-term debt	1,647,106	1,646,396
Operating lease liabilities	83,337	89,022
Other liabilities	49,543	51,190
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(867,721)	(829,678)
Accumulated other comprehensive income (loss)	5,604	(2,313)
Total Ferrellgas Partners, L.P. partners' deficit	(862,117)	(831,991)
Total liabilities and partners' capital (deficit)	1,668,741	1,682,098
Ferrellgas, L.P. [Member] | Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Current assets:
Cash and cash equivalents	1	1	$ 1	$ 1
Total current assets	1	1
Total assets	1	1
Current liabilities:
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	1	1
Total Ferrellgas Partners, L.P. partners' deficit	1	1
Total liabilities and partners' capital (deficit)	1	1
Ferrellgas, L.P. [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Current assets:
Accounts and notes receivable, net		24
Total current assets		24
Other assets, net	2,255	2,255
Total assets	2,255	2,279
Current liabilities:
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	2,255	2,279
Total Ferrellgas Partners, L.P. partners' deficit	2,255	2,279
Total liabilities and partners' capital (deficit)	2,255	2,279
Ferrellgas, L.P. [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	2,631	1,510
Accounts and notes receivable, net	103,941	89,535
Total current assets	106,572	91,045
Other assets, net	238	356
Total assets	106,810	91,401
Current liabilities:
Intercompany Payables	87,191	69,980
Other current liabilities	(15,946)	(13,961)
Total current liabilities	71,245	56,019
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	35,565	35,382
Total Ferrellgas Partners, L.P. partners' deficit	35,565	35,382
Total liabilities and partners' capital (deficit)	106,810	91,401
Ferrellgas, L.P. [Member] | Eliminations [Member]
Current assets:
Intercompany Receivables, Current	(87,191)	(69,980)
Total current assets	(87,191)	(69,980)
Investment in Ferrellgas, L.P.	(37,821)	(37,662)
Total assets	(125,012)	(107,642)
Current liabilities:
Intercompany Payables	(87,191)	(69,980)
Total current liabilities	(87,191)	(69,980)
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(37,821)	(37,662)
Total Ferrellgas Partners, L.P. partners' deficit	(37,821)	(37,662)
Total liabilities and partners' capital (deficit)	$ (125,012)	$ (107,642)