Guarantor financial information - Condensed Consolidated Statements of Earnings (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Revenues:
Propane and other gas liquids sales	$ 302,758	$ 242,399
Midstream operations	120,760	108,044
Other	31,137	29,099
Total revenues	454,655	379,542
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	179,515	119,212
Cost of sales - midstream operations	108,125	94,642
Cost of product sold - other	13,702	11,746
Operating expense	110,462	105,086
Depreciation and amortization expense	25,732	26,202
General and administrative expense	13,164	14,269
Equipment lease expense	6,741	7,349
Non-cash employee stock ownership plan compensation charge	3,962	3,754
Loss on disposal of assets	895	6,423
Operating income (loss)	(7,643)	(9,141)
Interest expense	(40,807)	(35,428)
Other income (expense), net	511	508
Earnings (loss) before income taxes	(47,939)	(44,061)
Income tax expense	377	(590)
Net earnings (loss)	(48,316)	(43,471)
Other comprehensive income (loss)	18,500	9,376
Comprehensive income	(29,816)	(34,095)
Ferrellgas, L.P. [Member]
Revenues:
Propane and other gas liquids sales	302,758	242,399
Midstream operations	120,760	108,044
Other	31,137	29,099
Total revenues	454,655	379,542
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	179,515	119,212
Cost of sales - midstream operations	108,125	94,642
Cost of product sold - other	13,702	11,746
Operating expense	110,462	105,086
Depreciation and amortization expense	25,732	26,202
General and administrative expense	13,164	14,269
Equipment lease expense	6,741	7,349
Non-cash employee stock ownership plan compensation charge	3,962	3,754
Loss on disposal of assets	895	6,423
Operating income (loss)	(7,643)	(9,141)
Interest expense	(32,196)	(31,398)
Other income (expense), net	511	508
Earnings (loss) before income taxes	(39,328)	(40,031)
Income tax expense	371	(591)
Equity in earnings of subsidiary	0	0
Net earnings (loss)	(39,699)	(39,440)
Other comprehensive income (loss)	18,500	9,376
Comprehensive income	(21,199)	(30,064)
Reportable Legal Entities [Member] | Ferrellgas, L.P. (Parent and Co-Issuer) [Member]
Revenues:
Propane and other gas liquids sales	302,117	242,399
Midstream operations	0	0
Other	16,677	17,326
Total revenues	318,794	259,725
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	178,819	119,212
Cost of sales - midstream operations	0	0
Cost of product sold - other	2,709	2,430
Operating expense	101,232	97,655
Depreciation and amortization expense	18,347	18,277
General and administrative expense	10,755	12,863
Equipment lease expense	6,648	7,210
Non-cash employee stock ownership plan compensation charge	3,962	3,754
Loss on disposal of assets	908	1,447
Operating income (loss)	(4,586)	(3,123)
Interest expense	(20,394)	(20,352)
Other income (expense), net	215	(47)
Earnings (loss) before income taxes	(24,765)	(23,522)
Income tax expense	(10)	(29)
Equity in earnings of subsidiary	(14,944)	(15,947)
Net earnings (loss)	(39,699)	(39,440)
Other comprehensive income (loss)	18,500	9,376
Comprehensive income	(21,199)	(30,064)
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Revenues:
Propane and other gas liquids sales	641	0
Midstream operations	120,760	108,044
Other	14,460	11,773
Total revenues	135,861	119,817
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	696	0
Cost of sales - midstream operations	108,125	94,642
Cost of product sold - other	10,993	9,316
Operating expense	9,263	10,246
Depreciation and amortization expense	7,313	7,872
General and administrative expense	2,407	1,404
Equipment lease expense	93	139
Non-cash employee stock ownership plan compensation charge	0	0
Loss on disposal of assets	(13)	4,976
Operating income (loss)	(3,016)	(8,778)
Interest expense	(11,185)	(10,673)
Other income (expense), net	296	555
Earnings (loss) before income taxes	(13,905)	(18,896)
Income tax expense	381	(562)
Equity in earnings of subsidiary	0	0
Net earnings (loss)	(14,286)	(18,334)
Other comprehensive income (loss)	0	0
Comprehensive income	(14,286)	(18,334)
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Revenues:
Propane and other gas liquids sales	0	0
Midstream operations	0	0
Other	0	0
Total revenues	0	0
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	0	0
Cost of sales - midstream operations	0	0
Cost of product sold - other	0	0
Operating expense	1,182	(2,105)
Depreciation and amortization expense	72	53
General and administrative expense	0	0
Equipment lease expense	0	0
Non-cash employee stock ownership plan compensation charge	0	0
Loss on disposal of assets	0	0
Operating income (loss)	(1,254)	2,052
Interest expense	(617)	(370)
Other income (expense), net	1,215	707
Earnings (loss) before income taxes	(656)	2,389
Income tax expense	0	0
Equity in earnings of subsidiary	0	0
Net earnings (loss)	(656)	2,389
Other comprehensive income (loss)	0	0
Comprehensive income	(656)	2,389
Reportable Legal Entities [Member] | Ferrellgas Finance Corp. (Co-Issuer) [Member]
Revenues:
Propane and other gas liquids sales	0	0
Midstream operations	0	0
Other	0	0
Total revenues	0	0
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	0	0
Cost of sales - midstream operations	0	0
Cost of product sold - other	0	0
Operating expense	0	0
Depreciation and amortization expense	0	0
General and administrative expense	2	2
Equipment lease expense	0	0
Non-cash employee stock ownership plan compensation charge	0	0
Loss on disposal of assets	0	0
Operating income (loss)	(2)	(2)
Interest expense	0	0
Other income (expense), net	0	0
Earnings (loss) before income taxes	(2)	(2)
Income tax expense	0	0
Equity in earnings of subsidiary	0	0
Net earnings (loss)	(2)	(2)
Other comprehensive income (loss)	0	0
Comprehensive income	(2)	(2)
Eliminations [Member]
Revenues:
Propane and other gas liquids sales	0	0
Midstream operations	0	0
Other	0	0
Total revenues	0	0
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	0	0
Cost of sales - midstream operations	0	0
Cost of product sold - other	0	0
Operating expense	(1,215)	(710)
Depreciation and amortization expense	0	0
General and administrative expense	0	0
Equipment lease expense	0	0
Non-cash employee stock ownership plan compensation charge	0	0
Loss on disposal of assets	0	0
Operating income (loss)	1,215	710
Interest expense	0	(3)
Other income (expense), net	(1,215)	(707)
Earnings (loss) before income taxes	0	0
Income tax expense	0	0
Equity in earnings of subsidiary	14,944	15,947
Net earnings (loss)	14,944	15,947
Other comprehensive income (loss)	0	0
Comprehensive income	$ 14,944	$ 15,947