Guarantor financial information - Condensed Consolidated Statements of Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Revenues:
Propane and other gas liquids sales	$ 451,302	$ 369,437	$ 1,346,299	$ 1,049,211
Midstream operations	22,595	126,676	260,631	331,507
Other	41,913	41,996	118,691	116,183
Total revenues	515,810	538,109	1,725,621	1,496,901
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	260,419	197,487	802,852	551,728
Cost of sales - midstream operations	14,518	118,767	229,710	300,433
Cost of product sold - other	19,850	20,810	54,339	53,213
Operating expense	116,579	104,773	350,757	322,935
Depreciation and amortization expense	25,348	25,737	76,565	77,546
General and administrative expense	11,678	9,978	39,733	36,526
Equipment lease expense	7,133	7,270	20,828	22,035
Non-cash employee stock ownership plan compensation charge	2,738	4,697	10,731	11,396
Asset Impairment Charges	0	0	10,005	0
Loss on asset sales and disposals	6,270	2,393	46,414	8,861
Operating income (loss)	51,277	46,197	83,687	112,228
Interest expense	(40,375)	(39,860)	(123,855)	(112,107)
Other income (expense), net	227	162	1,422	1,433
Earnings (loss) before income taxes	11,129	6,499	(38,746)	1,554
Income tax expense (benefit)	67	(192)	282	(194)
Net earnings (loss)	11,062	6,691	(39,028)	1,748
Other comprehensive income (loss)	(6,727)	(8,429)	3,102	16,723
Comprehensive income (loss)	4,335	(1,738)	(35,926)	18,471
Ferrellgas, L.P. [Member]
Revenues:
Propane and other gas liquids sales	451,302	369,437	1,346,299	1,049,211
Midstream operations	22,595	126,676	260,631	331,507
Other	41,913	41,996	118,691	116,183
Total revenues	515,810	538,109	1,725,621	1,496,901
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	260,419	197,487	802,852	551,728
Cost of sales - midstream operations	14,518	118,767	229,710	300,433
Cost of product sold - other	19,850	20,810	54,339	53,213
Operating expense	116,579	104,773	350,757	322,935
Depreciation and amortization expense	25,348	25,737	76,565	77,546
General and administrative expense	11,546	9,869	39,600	36,416
Equipment lease expense	7,133	7,270	20,828	22,035
Non-cash employee stock ownership plan compensation charge	2,738	4,697	10,731	11,396
Asset Impairment Charges	0	0	10,005	0
Loss on asset sales and disposals	6,270	2,393	46,414	8,861
Operating income (loss)	51,409	46,306	83,820	112,338
Interest expense	(31,739)	(31,270)	(97,993)	(95,416)
Other income (expense), net	227	162	1,422	1,433
Earnings (loss) before income taxes	19,897	15,198	(12,751)	18,355
Income tax expense (benefit)	57	(197)	261	(200)
Equity in earnings of subsidiary	0	0	0	0
Net earnings (loss)	19,840	15,395	(13,012)	18,555
Other comprehensive income (loss)	(6,727)	(8,429)	3,102	16,723
Comprehensive income (loss)	13,113	6,966	(9,910)	35,278
Reportable Legal Entities [Member] | Ferrellgas, L.P. (Parent and Co-Issuer) [Member]
Revenues:
Propane and other gas liquids sales	451,212	369,437	1,345,604	1,049,211
Midstream operations	0	0	0	0
Other	19,701	17,850	59,085	56,785
Total revenues	470,913	387,287	1,404,689	1,105,996
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	260,317	197,487	802,063	551,728
Cost of sales - midstream operations	0	0	0	0
Cost of product sold - other	2,328	1,992	7,890	6,993
Operating expense	108,291	96,264	323,619	297,905
Depreciation and amortization expense	19,105	18,261	55,973	54,552
General and administrative expense	10,460	8,930	35,048	32,886
Equipment lease expense	7,045	7,108	20,555	21,585
Non-cash employee stock ownership plan compensation charge	2,738	4,697	10,731	11,396
Asset Impairment Charges			0
Loss on asset sales and disposals	2,243	2,146	3,706	3,666
Operating income (loss)	58,386	50,402	145,104	125,285
Interest expense	(20,297)	(19,452)	(61,903)	(60,893)
Other income (expense), net	(133)	(157)	490	100
Earnings (loss) before income taxes	37,956	30,793	83,691	64,492
Income tax expense (benefit)	102	97	174	171
Equity in earnings of subsidiary	(18,014)	(15,301)	(96,529)	(45,766)
Net earnings (loss)	19,840	15,395	(13,012)	18,555
Other comprehensive income (loss)	(6,727)	(8,429)	3,102	16,723
Comprehensive income (loss)	13,113	6,966	(9,910)	35,278
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Revenues:
Propane and other gas liquids sales	90	0	695	0
Midstream operations	22,595	126,676	260,631	331,507
Other	22,212	24,146	59,606	59,398
Total revenues	44,897	150,822	320,932	390,905
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	102	0	789	0
Cost of sales - midstream operations	14,518	118,767	229,710	300,433
Cost of product sold - other	17,522	18,818	46,449	46,220
Operating expense	9,262	8,594	28,320	28,482
Depreciation and amortization expense	6,171	7,418	20,377	22,817
General and administrative expense	1,086	939	4,547	3,525
Equipment lease expense	88	162	273	450
Non-cash employee stock ownership plan compensation charge	0	0	0	0
Asset Impairment Charges			10,005
Loss on asset sales and disposals	4,027	247	42,708	5,195
Operating income (loss)	(7,879)	(4,123)	(62,246)	(16,217)
Interest expense	(10,104)	(11,019)	(33,028)	(32,694)
Other income (expense), net	360	319	932	1,333
Earnings (loss) before income taxes	(17,623)	(14,823)	(94,342)	(47,578)
Income tax expense (benefit)	(45)	(294)	87	(371)
Equity in earnings of subsidiary	0	0	0	0
Net earnings (loss)	(17,578)	(14,529)	(94,429)	(47,207)
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss)	(17,578)	(14,529)	(94,429)	(47,207)
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Revenues:
Propane and other gas liquids sales	0	0	0	0
Midstream operations	0	0	0	0
Other	0	0	0	0
Total revenues	0	0	0	0
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	0	0	0	0
Cost of sales - midstream operations	0	0	0	0
Cost of product sold - other	0	0	0	0
Operating expense	1,459	1,315	4,474	(251)
Depreciation and amortization expense	72	58	215	177
General and administrative expense	0	0	0	0
Equipment lease expense	0	0	0	0
Non-cash employee stock ownership plan compensation charge	0	0	0	0
Asset Impairment Charges			0
Loss on asset sales and disposals	0	0	0	0
Operating income (loss)	(1,531)	(1,373)	(4,689)	74
Interest expense	(1,338)	(799)	(3,062)	(1,826)
Other income (expense), net	2,433	1,400	5,656	3,198
Earnings (loss) before income taxes	(436)	(772)	(2,095)	1,446
Income tax expense (benefit)	0	0	0	0
Equity in earnings of subsidiary	0	0	0	0
Net earnings (loss)	(436)	(772)	(2,095)	1,446
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss)	(436)	(772)	(2,095)	1,446
Reportable Legal Entities [Member] | Ferrellgas Finance Corp. (Co-Issuer) [Member]
Revenues:
Propane and other gas liquids sales	0	0	0	0
Midstream operations	0	0	0	0
Other	0	0	0	0
Total revenues	0	0	0	0
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	0	0	0	0
Cost of sales - midstream operations	0	0	0	0
Cost of product sold - other	0	0	0	0
Operating expense	0	0	0	0
Depreciation and amortization expense	0	0	0	0
General and administrative expense	0	0	5	5
Equipment lease expense	0	0	0	0
Non-cash employee stock ownership plan compensation charge	0	0	0	0
Asset Impairment Charges			0
Loss on asset sales and disposals	0	0	0	0
Operating income (loss)	0	0	(5)	(5)
Interest expense	0	0	0	0
Other income (expense), net	0	0	0	0
Earnings (loss) before income taxes	0	0	(5)	(5)
Income tax expense (benefit)	0	0	0	0
Equity in earnings of subsidiary	0	0	0	0
Net earnings (loss)	0	0	(5)	(5)
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss)	0	0	(5)	(5)
Eliminations [Member]
Revenues:
Propane and other gas liquids sales	0	0	0	0
Midstream operations	0	0	0	0
Other	0	0	0	0
Total revenues	0	0	0	0
Costs and expenses:
Cost of product sold - propane and other gas liquids sales	0	0	0	0
Cost of sales - midstream operations	0	0	0	0
Cost of product sold - other	0	0	0	0
Operating expense	(2,433)	(1,400)	(5,656)	(3,201)
Depreciation and amortization expense	0	0	0	0
General and administrative expense	0	0	0	0
Equipment lease expense	0	0	0	0
Non-cash employee stock ownership plan compensation charge	0	0	0	0
Asset Impairment Charges			0
Loss on asset sales and disposals	0	0	0	0
Operating income (loss)	2,433	1,400	5,656	3,201
Interest expense	0	0	0	(3)
Other income (expense), net	(2,433)	(1,400)	(5,656)	(3,198)
Earnings (loss) before income taxes	0	0	0	0
Income tax expense (benefit)	0	0	0	0
Equity in earnings of subsidiary	18,014	15,301	96,529	45,766
Net earnings (loss)	18,014	15,301	96,529	45,766
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss)	$ 18,014	$ 15,301	$ 96,529	$ 45,766