Guarantor financial information - Statements of Earnings (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Revenues:
Revenues	$ 279,081	$ 479,625	$ 573,377	$ 352,309	$ 347,521	$ 515,810	$ 755,156	$ 454,655	$ 433,376	$ 538,109	$ 579,250	$ 379,542	$ 1,684,392	$ 2,073,142	$ 1,930,277
Costs and expenses:
Operating expense													468,868	471,748	432,412
Depreciation and amortization expense													78,846	101,795	103,351
General and administrative expense													59,994	54,401	49,617
Equipment lease expense													33,073	28,272	29,124
Non-cash employee stock ownership plan compensation charge													5,693	13,859	15,088
Asset impairments							10,000						0	10,005	0
Loss on asset sales and disposals													10,968	187,399	14,457
Operating Income (Loss)													113,028	(91,964)	95,367
Interest expense													(177,619)	(168,467)	(152,485)
Other income, net													369	928	1,474
Earnings (loss) before income taxes													(64,222)	(259,503)	(55,644)
Income tax expense (benefit)													323	(2,678)	(1,143)
Net loss	(71,672)	20,760	43,875	(57,508)	(217,797)	11,062	(1,774)	(48,316)	(56,249)	6,691	38,528	(43,471)	(64,545)	(256,825)	(54,501)
Other comprehensive income (loss)													(35,380)	5,969	25,324
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													(99,925)	(250,856)	(29,177)
Propane [Member]
Revenues:
Revenues													1,608,858	1,642,976	1,318,412
Costs and expenses:
Cost of sales													902,516	973,414	694,155
Midstream Operations [Member]
Revenues:
Revenues														282,319	466,703
Costs and expenses:
Cost of sales														255,559	429,439
Other Revenues
Revenues:
Revenues													75,534	147,847	145,162
Costs and expenses:
Cost of sales													11,406	68,654	67,267
Parent Company [Member]
Costs and expenses:
General and administrative expense													14	137	139
Operating Income (Loss)													(29,233)	(220,039)	(28,904)
Interest expense													(34,984)	(34,521)	(25,297)
Income tax expense (benefit)													30	21	6
Equity in earnings (loss) of Ferrellgas, L.P.													(29,219)	(219,902)	(28,765)
Net loss													(64,247)	(254,581)	(54,207)
Ferrellgas, L.P. [Member]
Revenues:
Revenues	279,081	479,625	573,377	352,309	347,521	515,810	755,156	454,655	433,376	538,109	579,250	379,542	1,684,392	2,073,142	1,930,277
Costs and expenses:
Operating expense													468,868	471,748	432,412
Depreciation and amortization expense													78,846	101,795	103,351
General and administrative expense													59,980	54,264	49,478
Equipment lease expense													33,073	28,272	29,124
Non-cash employee stock ownership plan compensation charge													5,693	13,859	15,088
Asset impairments													0	10,005	0
Loss on asset sales and disposals													10,968	187,399	14,457
Operating Income (Loss)													113,042	(91,827)	95,506
Interest expense													(142,635)	(133,946)	(127,188)
Other income, net													369	928	1,474
Earnings (loss) before income taxes													(29,224)	(224,845)	(30,208)
Income tax expense (benefit)													293	(2,699)	(1,149)
Equity in earnings (loss) of Ferrellgas, L.P.													0	0	0
Net loss	$ (62,874)	$ 29,554	$ 52,617	$ (48,814)	$ (209,134)	$ 19,840	$ 6,847	$ (39,699)	$ (47,614)	$ 15,395	$ 42,600	$ (39,440)	(29,517)	(222,146)	(29,059)
Other comprehensive income (loss)													(35,380)	5,969	25,324
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													(64,897)	(216,177)	(3,735)
Ferrellgas, L.P. [Member] | Propane [Member]
Revenues:
Revenues													1,608,858	1,642,976	1,318,412
Costs and expenses:
Cost of sales													902,516	973,414	694,155
Ferrellgas, L.P. [Member] | Midstream Operations [Member]
Revenues:
Revenues														282,319	466,703
Costs and expenses:
Cost of sales														255,559	429,439
Ferrellgas, L.P. [Member] | Other Revenues
Revenues:
Revenues													75,534	147,847	145,162
Costs and expenses:
Cost of sales													11,406	68,654	67,267
Reportable Legal Entities [Member] | Parent Company [Member]
Revenues:
Revenues													1,684,343
Costs and expenses:
Operating expense													469,652	436,962	398,584
Depreciation and amortization expense													78,400	75,163	72,919
General and administrative expense													59,974	48,337	44,810
Equipment lease expense													33,073	27,939	28,560
Non-cash employee stock ownership plan compensation charge													5,693	13,859	15,088
Asset impairments														0
Loss on asset sales and disposals													8,289	8,978	9,198
Operating Income (Loss)													115,454	121,293	116,587
Interest expense													(132,929)	(86,646)	(80,866)
Other income, net													428	(234)	850
Earnings (loss) before income taxes													(17,047)	34,413	36,571
Income tax expense (benefit)													105	222	217
Equity in earnings (loss) of Ferrellgas, L.P.													(12,365)	(256,337)	(65,413)
Net loss													(29,517)	(222,146)	(29,059)
Other comprehensive income (loss)													(35,380)	5,969	25,324
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													(64,897)	(216,177)	(3,735)
Reportable Legal Entities [Member] | Parent Company [Member] | Propane [Member]
Revenues:
Revenues													1,608,858
Costs and expenses:
Cost of sales													902,516	972,467	694,155
Reportable Legal Entities [Member] | Parent Company [Member] | Midstream Operations [Member]
Costs and expenses:
Cost of sales														0	0
Reportable Legal Entities [Member] | Parent Company [Member] | Other Revenues
Revenues:
Revenues													75,485
Costs and expenses:
Cost of sales													11,292	10,111	8,473
Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Revenues:
Revenues													0
Costs and expenses:
Operating expense													0	0	0
Depreciation and amortization expense													0	0	0
General and administrative expense													6	5	5
Equipment lease expense													0	0	0
Non-cash employee stock ownership plan compensation charge													0	0	0
Asset impairments														0
Loss on asset sales and disposals													0	0	0
Operating Income (Loss)													(6)	(5)	(5)
Interest expense													0	0	0
Other income, net													0	0	0
Earnings (loss) before income taxes													(6)	(5)	(5)
Income tax expense (benefit)													0	0	0
Equity in earnings (loss) of Ferrellgas, L.P.													0	0	0
Net loss													(6)	(5)	(5)
Other comprehensive income (loss)													0	0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													(6)	(5)	(5)
Reportable Legal Entities [Member] | Subsidiary Issuer [Member] | Propane [Member]
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													0	0	0
Reportable Legal Entities [Member] | Subsidiary Issuer [Member] | Midstream Operations [Member]
Costs and expenses:
Cost of sales														0	0
Reportable Legal Entities [Member] | Subsidiary Issuer [Member] | Other Revenues
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													0	0	0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Revenues:
Revenues													49
Costs and expenses:
Operating expense													37	37,617	38,188
Depreciation and amortization expense													0	26,317	30,183
General and administrative expense													0	5,922	4,663
Equipment lease expense													0	333	564
Non-cash employee stock ownership plan compensation charge													0	0	0
Asset impairments														10,005
Loss on asset sales and disposals													2,679	178,421	5,259
Operating Income (Loss)													(2,781)	(215,631)	(25,187)
Interest expense													(38)	(43,247)	(43,839)
Other income, net													(59)	1,162	624
Earnings (loss) before income taxes													(2,878)	(257,716)	(68,402)
Income tax expense (benefit)													188	(2,921)	(1,366)
Equity in earnings (loss) of Ferrellgas, L.P.													0	0	0
Net loss													(3,066)	(254,795)	(67,036)
Other comprehensive income (loss)													0	0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													(3,066)	(254,795)	(67,036)
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Propane [Member]
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													0	947	0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Midstream Operations [Member]
Costs and expenses:
Cost of sales														255,559	429,439
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Other Revenues
Revenues:
Revenues													49
Costs and expenses:
Cost of sales													114	58,543	58,794
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Revenues:
Revenues													0
Costs and expenses:
Operating expense													3,589	4,755	95
Depreciation and amortization expense													446	315	249
General and administrative expense													0	0	0
Equipment lease expense													0	0	0
Non-cash employee stock ownership plan compensation charge													0	0	0
Asset impairments														0
Loss on asset sales and disposals													0	0	0
Operating Income (Loss)													(4,035)	(5,070)	(344)
Interest expense													(9,668)	(4,053)	(2,480)
Other income, net													4,410	7,586	4,452
Earnings (loss) before income taxes													(9,293)	(1,537)	1,628
Income tax expense (benefit)													0	0	0
Equity in earnings (loss) of Ferrellgas, L.P.													0	0	0
Net loss													(9,293)	(1,537)	1,628
Other comprehensive income (loss)													0	0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													(9,293)	(1,537)	1,628
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member] | Propane [Member]
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													0	0	0
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member] | Midstream Operations [Member]
Costs and expenses:
Cost of sales														0	0
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member] | Other Revenues
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													0	0	0
Eliminations [Member]
Revenues:
Revenues													0
Costs and expenses:
Operating expense													(4,410)	(7,586)	(4,455)
Depreciation and amortization expense													0	0	0
General and administrative expense													0	0	0
Equipment lease expense													0	0	0
Non-cash employee stock ownership plan compensation charge													0	0	0
Asset impairments														0
Loss on asset sales and disposals													0	0	0
Operating Income (Loss)													4,410	7,586	4,455
Interest expense													0	0	(3)
Other income, net													(4,410)	(7,586)	(4,452)
Earnings (loss) before income taxes													0	0	0
Income tax expense (benefit)													0	0	0
Equity in earnings (loss) of Ferrellgas, L.P.													12,365	256,337	65,413
Net loss													12,365	256,337	65,413
Other comprehensive income (loss)													0	0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest													12,365	256,337	65,413
Eliminations [Member] | Propane [Member]
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													0	0	0
Eliminations [Member] | Midstream Operations [Member]
Costs and expenses:
Cost of sales														0	0
Eliminations [Member] | Other Revenues
Revenues:
Revenues													0
Costs and expenses:
Cost of sales													$ 0	0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other Revenues
Revenues:
Revenues														147,847	145,162
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Ferrellgas, L.P. [Member]
Revenues:
Revenues														2,073,142	1,930,277
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Ferrellgas, L.P. [Member] | Propane [Member]
Revenues:
Revenues														1,642,976	1,318,412
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Ferrellgas, L.P. [Member] | Midstream Operations [Member]
Revenues:
Revenues														282,319	466,703
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Ferrellgas, L.P. [Member] | Other Revenues
Revenues:
Revenues														147,847	145,162
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Parent Company [Member]
Revenues:
Revenues														1,715,109	1,388,374
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Parent Company [Member] | Propane [Member]
Revenues:
Revenues														1,642,155	1,318,412
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Parent Company [Member] | Midstream Operations [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Parent Company [Member] | Other Revenues
Revenues:
Revenues														72,954	69,962
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Subsidiary Issuer [Member] | Propane [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Subsidiary Issuer [Member] | Midstream Operations [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Subsidiary Issuer [Member] | Other Revenues
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Revenues:
Revenues														358,033	541,903
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Propane [Member]
Revenues:
Revenues														821	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Midstream Operations [Member]
Revenues:
Revenues														282,319	466,703
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member] | Other Revenues
Revenues:
Revenues														74,893	75,200
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member] | Propane [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member] | Midstream Operations [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member] | Other Revenues
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Eliminations [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Eliminations [Member] | Propane [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Eliminations [Member] | Midstream Operations [Member]
Revenues:
Revenues														0	0
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Eliminations [Member] | Other Revenues
Revenues:
Revenues														$ 0	$ 0