Guarantor financial information - Balance Sheets (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2018	Jul. 31, 2018
Current assets:
Cash and cash equivalents	$ 29,805	$ 11,054	$ 63,188	$ 119,311
Accounts and notes receivable, net	123,841	107,596
Inventories	84,995	80,454
Prepaid expenses and other current assets	50,582	42,275
Total current assets	289,223	241,379
Property, plant and equipment, net	598,887	596,723
Goodwill, net	247,195	247,195
Intangible assets, net	108,493	108,557
Operating lease, right-of-use assets	124,047
Other assets, net	75,443	69,105
Total assets	1,443,288	1,262,959
Current liabilities:
Accounts payable	44,421	33,364
Short-term borrowings	80,000	43,000
Collateralized note payable	73,000	62,000
Current portion of long-term debt	358,080	631,756
Current operating lease liabilities	33,832
Other current liabilities	187,731	138,237
Total current liabilities	777,064	908,357
Long-term debt	1,731,920	1,457,004
Operating lease liabilities	88,773
Other liabilities	36,915	36,536
Contingencies and commitments
Partners' capital (deficit)
Accumulated other comprehensive income (loss)	(20,598)	(14,512)
Total Ferrellgas Partners, L.P. partners' deficit	(1,183,237)	(1,131,233)
Total liabilities and partners' capital (deficit)	1,443,288	1,262,959
Ferrellgas, L.P. [Member]
Current assets:
Cash and cash equivalents	29,733	11,046	63,093	119,308
Accounts and notes receivable, net	123,841	107,596
Inventories	84,995	80,454
Prepaid expenses and other current assets	50,426	42,157
Total current assets	288,995	241,253
Property, plant and equipment, net	598,887	596,723
Goodwill, net	247,195	247,195
Intangible assets, net	108,493	108,557
Operating lease, right-of-use assets	124,047
Other assets, net	75,443	69,105
Total assets	1,443,060	1,262,833
Current liabilities:
Accounts payable	44,421	33,364
Short-term borrowings	80,000	43,000
Collateralized note payable	73,000	62,000
Current portion of long-term debt	2,230	277,029
Current operating lease liabilities	33,832
Other current liabilities	176,099	134,303
Total current liabilities	409,582	549,696
Long-term debt	1,731,920	1,457,004
Operating lease liabilities	88,773
Other liabilities	36,915	36,536
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(803,335)	(765,756)
Accumulated other comprehensive income (loss)	(20,795)	(14,647)
Total Ferrellgas Partners, L.P. partners' deficit	(824,130)	(780,403)
Total liabilities and partners' capital (deficit)	1,443,060	1,262,833
Reportable Legal Entities [Member] | Ferrellgas, L.P. [Member] | Parent Company [Member]
Current assets:
Cash and cash equivalents	29,732	11,045	62,786	119,133
Accounts and notes receivable, net	7,891	(3,912)
Intercompany Receivables, Current	(7,736)	(5,650)
Inventories	84,995	80,454
Prepaid expenses and other current assets	50,426	42,158
Total current assets	165,308	124,095
Property, plant and equipment, net	598,887	596,724
Goodwill, net	247,195	247,195
Intangible assets, net	108,493	108,557
Investment in Ferrellgas, L.P.	55,600	52,999
Operating lease, right-of-use assets	124,047
Other assets, net	72,517	65,447
Total assets	1,372,047	1,195,017
Current liabilities:
Accounts payable	44,421	33,252
Short-term borrowings	80,000	43,000
Current portion of long-term debt	2,230	277,029
Current operating lease liabilities	33,832
Other current liabilities	178,086	128,666
Total current liabilities	338,569	481,947
Long-term debt	1,731,920	1,457,004
Operating lease liabilities	88,773
Other liabilities	36,915	36,469
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(803,335)	(765,756)
Accumulated other comprehensive income (loss)	(20,795)	(14,647)
Total Ferrellgas Partners, L.P. partners' deficit	(824,130)	(780,403)
Total liabilities and partners' capital (deficit)	1,372,047	1,195,017
Reportable Legal Entities [Member] | Ferrellgas, L.P. [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
Reportable Legal Entities [Member] | Ferrellgas, L.P. [Member] | Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents			$ 306	$ 174
Accounts and notes receivable, net	30	35
Prepaid expenses and other current assets		(1)
Total current assets	30	34
Property, plant and equipment, net		(1)
Other assets, net	2,255	2,875
Total assets	2,285	2,908
Current liabilities:
Intercompany Payables		(192)
Other current liabilities	13	20
Total current liabilities	13	(172)
Other liabilities		67
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	2,272	3,013
Total Ferrellgas Partners, L.P. partners' deficit	2,272	3,013
Total liabilities and partners' capital (deficit)	2,285	2,908
Reportable Legal Entities [Member] | Ferrellgas, L.P. [Member] | Non-Guarantor Subsidiaries [Member]
Current assets:
Accounts and notes receivable, net	115,920	111,473
Total current assets	115,920	111,473
Other assets, net	671	783
Total assets	116,591	112,256
Current liabilities:
Accounts payable		112
Collateralized note payable	73,000	62,000
Intercompany Payables	(7,736)	(5,458)
Other current liabilities	(2,000)	5,617
Total current liabilities	63,264	62,271
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	53,327	49,985
Total Ferrellgas Partners, L.P. partners' deficit	53,327	49,985
Total liabilities and partners' capital (deficit)	116,591	112,256
Eliminations [Member] | Ferrellgas, L.P. [Member]
Current assets:
Intercompany Receivables, Current	7,736	5,650
Total current assets	7,736	5,650
Investment in Ferrellgas, L.P.	(55,600)	(52,999)
Total assets	(47,864)	(47,349)
Current liabilities:
Intercompany Payables	7,736	5,650
Total current liabilities	7,736	5,650
Contingencies and commitments
Partners' capital (deficit)
Partners' equity	(55,600)	(52,999)
Total Ferrellgas Partners, L.P. partners' deficit	(55,600)	(52,999)
Total liabilities and partners' capital (deficit)	$ (47,864)	$ (47,349)