Guarantor financial information - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Jul. 31, 2017	Apr. 30, 2017	Jul. 31, 2016
Current assets:
Cash and cash equivalents	$ 9,499	$ 5,760	$ 9,506	$ 4,965
Accounts and notes receivable	202,727	165,084
Inventories	85,062	92,552
Prepaid expenses and other current assets	44,090	33,388
Total current assets	341,378	296,784
Property, plant and equipment, net	637,688	731,923
Goodwill	246,098	256,103
Intangible assets, net	235,318	251,102
Other assets, net	72,094	74,057
Total assets	1,532,576	1,609,969
Current liabilities:
Accounts payable	52,472	85,561
Short-term borrowings	0	59,781
Collateralized note payable	104,000	69,000
Other current liabilities	158,875	126,224
Total current liabilities	315,347	340,566
Long-term debt	1,995,608	1,995,795
Other liabilities	34,225	31,118
Contingencies and commitments
Partners' capital
Partners' equity	(808,221)	(753,578)
Accumulated other comprehensive income (loss)	17,672	14,601
Total partners' capital (deficit)	(812,604)	(757,510)
Total liabilities and partners' capital (deficit)	1,532,576	1,609,969
Ferrellgas, L.P. [Member]
Current assets:
Cash and cash equivalents	9,491	5,701	9,166	4,890
Accounts and notes receivable	202,727	165,084
Intercompany receivables	0	0
Inventories	85,062	92,552
Prepaid expenses and other current assets	44,059	33,426
Total current assets	341,339	296,763
Property, plant and equipment, net	637,688	731,923
Goodwill	246,098	256,103
Intangible assets, net	235,318	251,102
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	72,094	74,057
Total assets	1,532,537	1,609,948
Current liabilities:
Accounts payable	52,472	85,561
Short-term borrowings	0	59,781
Collateralized note payable	104,000	69,000
Intercompany Payables	0	0
Other current liabilities	147,243	122,016
Total current liabilities	303,715	336,358
Long-term debt	1,646,069	1,649,270
Other liabilities	34,225	31,118
Contingencies and commitments
Partners' capital
Partners' equity	(469,338)	(421,562)
Accumulated other comprehensive income (loss)	17,866	14,764
Total partners' capital (deficit)	(451,472)	(406,798)
Total liabilities and partners' capital (deficit)	1,532,537	1,609,948
Reportable Legal Entities [Member] | Ferrellgas, L.P. (Parent and Co-Issuer) [Member]
Current assets:
Cash and cash equivalents	9,126	5,327	8,943	4,472
Accounts and notes receivable	(3,346)	(3,132)
Intercompany receivables	65,801	39,877
Inventories	70,893	78,963
Prepaid expenses and other current assets	31,167	26,106
Total current assets	173,641	147,141
Property, plant and equipment, net	552,551	537,582
Goodwill	246,098	246,098
Intangible assets, net	123,177	128,209
Intercompany receivables	450,000	450,000
Investments in consolidated subsidiaries	(164,031)	(53,915)
Other assets, net	36,744	35,862
Total assets	1,418,180	1,490,977
Current liabilities:
Accounts payable	50,164	44,026
Short-term borrowings	0	59,781
Collateralized note payable	0	0
Intercompany Payables	0	0
Other current liabilities	143,804	118,039
Total current liabilities	193,968	221,846
Long-term debt	1,646,069	1,649,139
Other liabilities	29,615	26,790
Partners' capital
Partners' equity	(469,338)	(421,562)
Accumulated other comprehensive income (loss)	17,866	14,764
Total partners' capital (deficit)	(451,472)	(406,798)
Total liabilities and partners' capital (deficit)	1,418,180	1,490,977
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	364	373	222	417
Accounts and notes receivable	23,493	58,618
Intercompany receivables	0	0
Inventories	14,169	13,589
Prepaid expenses and other current assets	12,890	7,314
Total current assets	50,916	79,894
Property, plant and equipment, net	85,137	194,341
Goodwill	0	10,005
Intangible assets, net	112,141	122,893
Intercompany receivables	0	0
Investments in consolidated subsidiaries	0	0
Other assets, net	34,987	37,618
Total assets	283,181	444,751
Current liabilities:
Accounts payable	2,221	41,345
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	45,554	41,645
Other current liabilities	3,041	3,776
Total current liabilities	50,816	86,766
Long-term debt	450,000	450,131
Other liabilities	4,610	4,300
Partners' capital
Partners' equity	(222,245)	(96,446)
Accumulated other comprehensive income (loss)	0	0
Total partners' capital (deficit)	(222,245)	(96,446)
Total liabilities and partners' capital (deficit)	283,181	444,751
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Accounts and notes receivable	182,580	109,598
Intercompany receivables	0	0
Inventories	0	0
Prepaid expenses and other current assets	2	6
Total current assets	182,582	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	363	577
Total assets	182,945	110,181
Current liabilities:
Accounts payable	87	190
Short-term borrowings	0	0
Collateralized note payable	104,000	69,000
Intercompany Payables	20,247	(1,768)
Other current liabilities	398	201
Total current liabilities	124,732	67,623
Long-term debt	0	0
Other liabilities	0	28
Partners' capital
Partners' equity	58,213	42,530
Accumulated other comprehensive income (loss)	0	0
Total partners' capital (deficit)	58,213	42,530
Total liabilities and partners' capital (deficit)	182,945	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 (deficit)	1	1
Total liabilities and partners' capital (deficit)	1	1
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts and notes receivable	0	0
Intercompany receivables	(65,801)	(39,877)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(65,801)	(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	164,031	53,915
Other assets, net	0	0
Total assets	(351,770)	(435,962)
Current liabilities:
Accounts payable	0	0
Short-term borrowings	0	0
Collateralized note payable	0	0
Intercompany Payables	(65,801)	(39,877)
Other current liabilities	0	0
Total current liabilities	(65,801)	(39,877)
Long-term debt	(450,000)	(450,000)
Other liabilities	0	0
Partners' capital
Partners' equity	164,031	53,915
Accumulated other comprehensive income (loss)	0	0
Total partners' capital (deficit)	164,031	53,915
Total liabilities and partners' capital (deficit)	$ (351,770)	$ (435,962)