Guarantor financial information - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Oct. 31, 2017	Jul. 31, 2017	Oct. 31, 2016	Jul. 31, 2016
Current assets:
Cash and cash equivalents	$ 7,100	$ 5,760	$ 12,639	$ 4,965
Accounts and notes receivable	191,428	165,084
Inventories	112,338	92,552
Prepaid expenses and other current assets	68,068	33,388
Total current assets	378,934	296,784
Property, plant and equipment, net	738,729	731,923
Goodwill	256,103	256,103
Intangible assets, net	250,629	251,102
Other assets, net	80,559	74,057
Total assets	1,704,954	1,609,969
Current liabilities:
Accounts payable	99,198	85,561
Short-term borrowings	263,200	59,781
Collateralized note payable	88,000	69,000
Other current liabilities	200,879	126,224
Total current liabilities	651,277	340,566
Long-term debt	1,812,155	1,995,795
Other liabilities	34,799	31,118
Contingencies and commitments
Partners' capital
Partners' equity	(789,069)	(753,578)
Accumulated other comprehensive income (loss)	32,915	14,601
Total partners' capital	(793,277)	(757,510)
Total liabilities and partners' capital	1,704,954	1,609,969
Ferrellgas, L.P. [Member]
Current assets:
Cash and cash equivalents	7,098	5,701	12,565	4,890
Accounts and notes receivable	191,428	165,084
Intercompany receivables	0	0
Inventories	112,338	92,552
Prepaid expenses and other current assets	68,055	33,426
Total current assets	378,919	296,763
Property, plant and equipment, net	738,729	731,923
Goodwill	256,103	256,103
Intangible assets, net	250,629	251,102
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	80,559	74,057
Total assets	1,704,939	1,609,948
Current liabilities:
Accounts payable	99,198	85,561
Short-term borrowings	263,200	59,781
Collateralized note payable	88,000	69,000
Intercompany Payables	0	0
Other current liabilities	189,261	122,016
Total current liabilities	639,659	336,358
Long-term debt	1,464,429	1,649,270
Other liabilities	34,799	31,118
Contingencies and commitments
Partners' capital
Partners' equity	(467,212)	(421,562)
Accumulated other comprehensive income (loss)	33,264	14,764
Total partners' capital	(433,948)	(406,798)
Total liabilities and partners' capital	1,704,939	1,609,948
Reportable Legal Entities [Member] | Ferrellgas, L.P. (Parent and Co-Issuer) [Member]
Current assets:
Cash and cash equivalents	6,852	5,327	12,368	4,472
Accounts and notes receivable	(2,343)	(3,132)
Intercompany receivables	40,190	39,877
Inventories	90,812	78,963
Prepaid expenses and other current assets	61,140	26,106
Total current assets	196,651	147,141
Property, plant and equipment, net	547,489	537,582
Goodwill	246,098	246,098
Intangible assets, net	131,322	128,209
Intercompany receivables	450,000	450,000
Investments in consolidated subsidiaries	(48,341)	(53,915)
Other assets, net	39,918	35,862
Total assets	1,563,137	1,490,977
Current liabilities:
Accounts payable	56,610	44,026
Short-term borrowings	263,200	59,781
Collateralized note payable	0	0
Intercompany Payables	0	0
Other current liabilities	182,794	118,039
Total current liabilities	502,604	221,846
Long-term debt	1,464,344	1,649,139
Other liabilities	30,137	26,790
Partners' capital
Partners' equity	(467,212)	(421,562)
Accumulated other comprehensive income (loss)	33,264	14,764
Total partners' capital	(433,948)	(406,798)
Total liabilities and partners' capital	1,563,137	1,490,977
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	245	373	196	417
Accounts and notes receivable	60,692	58,618
Intercompany receivables	0	0
Inventories	21,526	13,589
Prepaid expenses and other current assets	6,909	7,314
Total current assets	89,372	79,894
Property, plant and equipment, net	191,240	194,341
Goodwill	10,005	10,005
Intangible assets, net	119,307	122,893
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	40,136	37,618
Total assets	450,060	444,751
Current liabilities:
Accounts payable	42,167	41,345
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	42,952	41,645
Other current liabilities	6,238	3,776
Total current liabilities	91,357	86,766
Long-term debt	450,085	450,131
Other liabilities	4,662	4,300
Partners' capital
Partners' equity	(96,044)	(96,446)
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	(96,044)	(96,446)
Total liabilities and partners' capital	450,060	444,751
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Accounts and notes receivable	133,079	109,598
Intercompany receivables	0	0
Inventories	0	0
Prepaid expenses and other current assets	6	6
Total current assets	133,085	109,604
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	505	577
Total assets	133,590	110,181
Current liabilities:
Accounts payable	421	190
Short-term borrowings	0	0
Collateralized note payable	88,000	69,000
Intercompany Payables	(2,762)	(1,768)
Other current liabilities	229	201
Total current liabilities	85,888	67,623
Long-term debt	0	0
Other liabilities	0	28
Partners' capital
Partners' equity	47,702	42,530
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	47,702	42,530
Total liabilities and partners' capital	133,590	110,181
Reportable Legal Entities [Member] | Ferrellgas Finance Corp. (Co-Issuer) [Member]
Current assets:
Cash and cash equivalents	1	1	1	1
Accounts and notes receivable	0	0
Intercompany receivables	0	0
Inventories	0	0
Prepaid expenses and other current assets	0	0
Total current assets	1	1
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	0	0
Total assets	1	1
Current liabilities:
Accounts payable	0	0
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Long-term debt	0	0
Other liabilities	0	0
Partners' capital
Partners' equity	1	1
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	1	1
Total liabilities and partners' capital	1	1
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts and notes receivable	0	0
Intercompany receivables	(40,190)	(39,877)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(40,190)	(39,877)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Intercompany receivables	(450,000)	(450,000)
Investments in consolidated subsidiaries	48,341	53,915
Other assets, net	0	0
Total assets	(441,849)	(435,962)
Current liabilities:
Accounts payable	0	0
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	(40,190)	(39,877)
Other current liabilities	0	0
Total current liabilities	(40,190)	(39,877)
Long-term debt	(450,000)	(450,000)
Other liabilities	0	0
Partners' capital
Partners' equity	48,341	53,915
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	48,341	53,915
Total liabilities and partners' capital	$ (441,849)	$ (435,962)