Guarantor financial information - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jul. 31, 2017	Jan. 31, 2017	Jul. 31, 2016
Current assets:
Cash and cash equivalents	$ 14,173	$ 5,760	$ 14,710	$ 4,965
Accounts and notes receivable	255,978	165,084
Inventories	110,092	92,552
Assets held for sale	52,200	0
Prepaid expenses and other current assets	41,400	33,388
Total current assets	473,843	296,784
Property, plant and equipment, net	646,327	731,923
Goodwill	246,098	256,103
Intangible assets, net	243,079	251,102
Other assets, net	77,712	74,057
Total assets	1,687,059	1,609,969
Current liabilities:
Accounts payable	82,072	85,561
Short-term borrowings	261,200	59,781
Collateralized note payable	166,000	69,000
Other current liabilities	140,510	126,224
Total current liabilities	649,782	340,566
Long-term debt	1,811,617	1,995,795
Other liabilities	35,422	31,118
Contingencies and commitments
Partners' capital
Partners' equity	(805,318)	(753,578)
Accumulated other comprehensive income (loss)	24,332	14,601
Total partners' capital	(809,762)	(757,510)
Total liabilities and partners' capital	1,687,059	1,609,969
Ferrellgas, L.P. [Member]
Current assets:
Cash and cash equivalents	14,171	5,701	13,657	4,890
Accounts and notes receivable	255,978	165,084
Intercompany receivables	0	0
Inventories	110,092	92,552
Assets held for sale	52,200	0
Prepaid expenses and other current assets	41,393	33,426
Total current assets	473,834	296,763
Property, plant and equipment, net	646,327	731,923
Goodwill	246,098	256,103
Intangible assets, net	243,079	251,102
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	77,712	74,057
Total assets	1,687,050	1,609,948
Current liabilities:
Accounts payable	82,072	85,561
Short-term borrowings	261,200	59,781
Collateralized note payable	166,000	69,000
Intercompany Payables	0	0
Other current liabilities	136,591	122,016
Total current liabilities	645,863	336,358
Long-term debt	1,462,973	1,649,270
Other liabilities	35,422	31,118
Contingencies and commitments
Partners' capital
Partners' equity	(481,801)	(421,562)
Accumulated other comprehensive income (loss)	24,593	14,764
Total partners' capital	(457,208)	(406,798)
Total liabilities and partners' capital	1,687,050	1,609,948
Reportable Legal Entities [Member] | Ferrellgas, L.P. (Parent and Co-Issuer) [Member]
Current assets:
Cash and cash equivalents	13,954	5,327	13,344	4,472
Accounts and notes receivable	(3,004)	(3,132)
Intercompany receivables	37,988	39,877
Inventories	95,097	78,963
Assets held for sale	0
Prepaid expenses and other current assets	33,630	26,106
Total current assets	177,665	147,141
Property, plant and equipment, net	547,441	537,582
Goodwill	246,098	246,098
Intangible assets, net	127,316	128,209
Intercompany receivables	450,000	450,000
Investments in consolidated subsidiaries	(80,685)	(53,915)
Other assets, net	39,847	35,862
Total assets	1,507,682	1,490,977
Current liabilities:
Accounts payable	78,054	44,026
Short-term borrowings	261,200	59,781
Collateralized note payable	0	0
Intercompany Payables	0	0
Other current liabilities	132,047	118,039
Total current liabilities	471,301	221,846
Long-term debt	1,462,936	1,649,139
Other liabilities	30,653	26,790
Partners' capital
Partners' equity	(481,801)	(421,562)
Accumulated other comprehensive income (loss)	24,593	14,764
Total partners' capital	(457,208)	(406,798)
Total liabilities and partners' capital	1,507,682	1,490,977
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	216	373	312	417
Accounts and notes receivable	23,832	58,618
Intercompany receivables	0	0
Inventories	14,995	13,589
Assets held for sale	52,200
Prepaid expenses and other current assets	7,762	7,314
Total current assets	99,005	79,894
Property, plant and equipment, net	98,886	194,341
Goodwill	0	10,005
Intangible assets, net	115,763	122,893
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	37,432	37,618
Total assets	351,086	444,751
Current liabilities:
Accounts payable	3,926	41,345
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	44,259	41,645
Other current liabilities	4,074	3,776
Total current liabilities	52,259	86,766
Long-term debt	450,037	450,131
Other liabilities	4,769	4,300
Partners' capital
Partners' equity	(155,979)	(96,446)
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	(155,979)	(96,446)
Total liabilities and partners' capital	351,086	444,751
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Accounts and notes receivable	235,150	109,598
Intercompany receivables	0	0
Inventories	0	0
Assets held for sale	0
Prepaid expenses and other current assets	1	6
Total current assets	235,151	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	433	577
Total assets	235,584	110,181
Current liabilities:
Accounts payable	92	190
Short-term borrowings	0	0
Collateralized note payable	166,000	69,000
Intercompany Payables	(6,271)	(1,768)
Other current liabilities	470	201
Total current liabilities	160,291	67,623
Long-term debt	0	0
Other liabilities	0	28
Partners' capital
Partners' equity	75,293	42,530
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	75,293	42,530
Total liabilities and partners' capital	235,584	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
Assets held for sale	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	(37,988)	(39,877)
Inventories	0	0
Assets held for sale	0
Prepaid expenses and other current assets	0	0
Total current assets	(37,988)	(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	80,685	53,915
Other assets, net	0	0
Total assets	(407,303)	(435,962)
Current liabilities:
Accounts payable	0	0
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	(37,988)	(39,877)
Other current liabilities	0	0
Total current liabilities	(37,988)	(39,877)
Long-term debt	(450,000)	(450,000)
Other liabilities	0	0
Partners' capital
Partners' equity	80,685	53,915
Accumulated other comprehensive income (loss)	0	0
Total partners' capital	80,685	53,915
Total liabilities and partners' capital	$ (407,303)	$ (435,962)