Guarantor financial information - Balance Sheets (Details) - USD ($) $ in Thousands	Jan. 31, 2021	Jul. 31, 2020	Jan. 31, 2020	Jul. 31, 2019
Current assets:
Cash and cash equivalents	$ 326,483	$ 333,761	$ 13,706	$ 11,054
Accounts and notes receivable, net	206,280	101,438
Inventories	90,473	72,664
Prepaid expenses and other current assets	72,914	35,944
Total current assets	696,150	543,807
Property, plant and equipment, net	587,870	591,042
Goodwill, net	246,946	247,195
Intangible assets, net	99,644	104,049
Operating lease, right-of-use assets	97,249	107,349
Other assets, net	91,159	74,748
Total assets	1,819,018	1,668,190
Current liabilities:
Accounts payable	79,224	33,944
Current portion of long-term debt	501,865	859,095
Current operating lease liabilities	27,895	29,345
Other current liabilities	191,908	167,466
Total current liabilities	800,892	1,089,850
Long-term debt	1,650,410	1,646,396
Operating lease liabilities	80,901	89,022
Other liabilities	49,541	51,190
Partners' capital (deficit)
Accumulated other comprehensive income (loss)	33,762	(2,303)
Total Ferrellgas Partners, L.P. partners' deficit	(1,145,317)	(1,200,042)
Total liabilities and partners' capital (deficit)	1,819,018	1,668,190
Ferrellgas, L.P. [Member]
Current assets:
Cash and cash equivalents	306,577	333,755	13,643	11,046
Accounts and notes receivable, net	206,280	101,438
Inventories	90,473	72,664
Prepaid expenses and other current assets	73,106	35,897
Total current assets	676,436	543,754
Property, plant and equipment, net	587,870	591,042
Goodwill, net	246,946	247,195
Intangible assets, net	99,644	104,049
Operating lease, right-of-use assets	97,249	107,349
Loan receivable - Ferrellgas Partners, L.P.	20,151
Other assets, net	91,159	74,748
Total assets	1,819,455	1,668,137
Current liabilities:
Accounts payable	79,224	33,944
Current portion of long-term debt	501,865	502,095
Current operating lease liabilities	27,895	29,345
Other current liabilities	190,708	148,136
Total current liabilities	799,692	713,520
Long-term debt	1,650,410	1,646,396
Operating lease liabilities	80,901	89,022
Other liabilities	49,541	51,190
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(795,209)	(829,678)
Accumulated other comprehensive income (loss)	34,120	(2,313)
Total Ferrellgas Partners, L.P. partners' deficit	(761,089)	(831,991)
Total liabilities and partners' capital (deficit)	1,819,455	1,668,137
Ferrellgas, L.P. [Member] | Reportable Legal Entities [Member] | Parent Company [Member]
Current assets:
Cash and cash equivalents	300,436	332,244	13,642	11,045
Accounts and notes receivable, net	5,837	11,879
Intercompany Receivables, Current	169,668	69,980
Inventories	90,473	72,664
Prepaid expenses and other current assets	73,106	35,897
Total current assets	639,520	522,664
Property, plant and equipment, net	587,870	591,042
Goodwill, net	246,946	247,195
Intangible assets, net	99,644	104,049
Investment in Ferrellgas, L.P.	39,143	37,662
Operating lease, right-of-use assets	97,249	107,349
Loan receivable - Ferrellgas Partners, L.P.	20,151
Other assets, net	88,784	72,137
Total assets	1,819,307	1,682,098
Current liabilities:
Accounts payable	79,224	33,944
Current portion of long-term debt	501,865	502,095
Current operating lease liabilities	27,895	29,345
Other current liabilities	190,560	162,097
Total current liabilities	799,544	727,481
Long-term debt	1,650,410	1,646,396
Operating lease liabilities	80,901	89,022
Other liabilities	49,541	51,190
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(795,209)	(829,678)
Accumulated other comprehensive income (loss)	34,120	(2,313)
Total Ferrellgas Partners, L.P. partners' deficit	(761,089)	(831,991)
Total liabilities and partners' capital (deficit)	1,819,307	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:
Other current liabilities	(3)
Total current liabilities	(3)
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	2,258	2,279
Total Ferrellgas Partners, L.P. partners' deficit	2,258	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	6,140	1,510
Accounts and notes receivable, net	200,443	89,535
Total current assets	206,583	91,045
Other assets, net	120	356
Total assets	206,703	91,401
Current liabilities:
Intercompany Payables	169,668	69,980
Other current liabilities	151	(13,961)
Total current liabilities	169,819	56,019
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	36,884	35,382
Total Ferrellgas Partners, L.P. partners' deficit	36,884	35,382
Total liabilities and partners' capital (deficit)	206,703	91,401
Ferrellgas, L.P. [Member] | Eliminations [Member]
Current assets:
Intercompany Receivables, Current	(169,668)	(69,980)
Total current assets	(169,668)	(69,980)
Investment in Ferrellgas, L.P.	(39,143)	(37,662)
Total assets	(208,811)	(107,642)
Current liabilities:
Intercompany Payables	(169,668)	(69,980)
Total current liabilities	(169,668)	(69,980)
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(39,143)	(37,662)
Total Ferrellgas Partners, L.P. partners' deficit	(39,143)	(37,662)
Total liabilities and partners' capital (deficit)	$ (208,811)	$ (107,642)