Guarantor financial information - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 15,075	$ 74,148	$ 127,288
Cash flows from investing activities:
Business acquisitions, net of cash acquired	(13,551)	(18,141)	(3,539)
Capital expenditures	(108,822)	(84,919)	(50,472)
Proceeds from sale of assets	5,699	152,587	8,510
Cash payments to construct assets in connection with future lease transactions	(9,934)	0	0
Proceeds From Equipment On Lease	862	0	0
Other	1,419	0	(37)
Net cash used in investing activities	(124,327)	49,527	(45,538)
Cash flows from financing activities:
Distributions	(9,814)	(39,254)	(79,733)
Proceeds from issuance of long-term debt	0	323,680	230,864
Payments on long-term debt	(2,428)	(212,920)	(174,292)
Net additions to (reductions in) short-term borrowings	10,200	(51,379)	(41,510)
Net additions to (reductions in) collateralized short-term borrowings	4,000	(11,000)	5,000
Cash paid for financing costs	(548)	(18,535)	(6,078)
Net cash used in financing activities	995	(10,124)	(80,955)
Increase (decrease) in cash and cash equivalents	(108,257)	113,551	795
Cash and cash equivalents	11,054	119,311	5,760	$ 4,965
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(30,887)	(31,006)	(21,460)
Cash flows from investing activities:
Net cash used in investing activities	40,706	70,246	(47,319)
Cash flows from financing activities:
Distributions	(9,814)	(39,254)	(79,733)
Proceeds from issuance of long-term debt			168,000
Cash paid for financing costs		(42)	(3,653)
Net cash used in financing activities	(9,814)	(39,296)	68,763
Increase (decrease) in cash and cash equivalents	5	(56)	(16)
Cash and cash equivalents	8	3	59	75
Ferrellgas, L.P. [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	45,962	105,154	148,748
Cash flows from investing activities:
Business acquisitions, net of cash acquired	(13,551)	(18,141)	(3,539)
Capital expenditures	(108,822)	(84,919)	(50,472)
Proceeds from sale of assets	5,699	152,587	8,510
Cash payments to construct assets in connection with future lease transactions	(9,934)
Proceeds From Equipment On Lease	862
Cash collected for purchase of interest in accounts receivable	0	0	0
Cash remitted for accounts receivable	0	0	0
Net changes in advances with consolidated entities		0	0
Intercompany loan to affiliate	0
Other	1,419		(37)
Net cash used in investing activities	(124,327)	49,527	(45,538)
Cash flows from financing activities:
Distributions	(41,121)	(70,962)	(119,879)
Capital contribution			167,843
Proceeds from issuance of long-term debt		323,680	62,864
Payments on long-term debt	(2,428)	(212,920)	(174,292)
Net additions to (reductions in) short-term borrowings	10,200	(51,379)	(41,510)
Net additions to (reductions in) collateralized short-term borrowings	4,000	(11,000)	5,000
Net changes in advances with consolidated entities	0	0	0
Cash paid for financing costs	(548)	(18,493)	(2,425)
Net cash used in financing activities	(29,897)	(41,074)	(102,399)
Effect of exchange rate changes on cash			0
Increase (decrease) in cash and cash equivalents	(108,262)	113,607	811
Cash and cash equivalents	11,046	119,308	5,701	4,890
Reportable Legal Entities [Member] | Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	25,796	139,294	185,640
Cash flows from investing activities:
Business acquisitions, net of cash acquired	(13,551)	(18,141)	(3,539)
Capital expenditures	(108,822)	(81,114)	(49,107)
Proceeds from sale of assets	5,699	7,327	8,510
Cash payments to construct assets in connection with future lease transactions	(9,934)
Proceeds From Equipment On Lease	862
Cash collected for purchase of interest in accounts receivable	0	0	0
Cash remitted for accounts receivable	0	0	0
Net changes in advances with consolidated entities		96,514	(33,573)
Intercompany loan to affiliate	24,328
Other	1,419		(37)
Net cash used in investing activities	(99,999)	4,586	(77,746)
Cash flows from financing activities:
Distributions	(41,121)	(70,962)	(119,879)
Capital contribution			167,843
Proceeds from issuance of long-term debt		323,680	62,864
Payments on long-term debt	(2,428)	(212,920)	(174,292)
Net additions to (reductions in) short-term borrowings	10,200	(51,379)	(41,510)
Net additions to (reductions in) collateralized short-term borrowings	0	0	0
Net changes in advances with consolidated entities	0	0	0
Cash paid for financing costs	(536)	(18,493)	(2,065)
Net cash used in financing activities	(33,885)	(30,074)	(107,039)
Effect of exchange rate changes on cash			0
Increase (decrease) in cash and cash equivalents	(108,088)	113,806	855
Cash and cash equivalents	11,045	119,133	5,327	4,472
Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(6)	(5)	(5)
Cash flows from investing activities:
Business acquisitions, net of cash acquired	0	0	0
Capital expenditures	0	0	0
Proceeds from sale of assets	0	0	0
Cash payments to construct assets in connection with future lease transactions	0
Proceeds From Equipment On Lease	0
Cash collected for purchase of interest in accounts receivable	0	0	0
Cash remitted for accounts receivable	0	0	0
Net changes in advances with consolidated entities		0	0
Intercompany loan to affiliate	0
Other	0		0
Net cash used in investing activities	0	0	0
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution			0
Proceeds from issuance of long-term debt		0	0
Payments on long-term debt	0	0	0
Net additions to (reductions in) short-term borrowings	0	0	0
Net additions to (reductions in) collateralized short-term borrowings	0	0	0
Net changes in advances with consolidated entities	6	5	5
Cash paid for financing costs	0	0	0
Net cash used in financing activities	6	5	5
Effect of exchange rate changes on cash			0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents	1	1	1	1
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	24,889	(48,708)	(36,297)
Cash flows from investing activities:
Business acquisitions, net of cash acquired	0	0	0
Capital expenditures	0	(3,805)	(1,365)
Proceeds from sale of assets	0	145,260	0
Cash payments to construct assets in connection with future lease transactions	0
Proceeds From Equipment On Lease	0
Cash collected for purchase of interest in accounts receivable	0	0	0
Cash remitted for accounts receivable	0	0	0
Net changes in advances with consolidated entities		0	0
Intercompany loan to affiliate	0
Other	0		0
Net cash used in investing activities	0	141,455	(1,365)
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution			0
Proceeds from issuance of long-term debt		0	0
Payments on long-term debt	0	0	0
Net additions to (reductions in) short-term borrowings	0	0	0
Net additions to (reductions in) collateralized short-term borrowings	0	0	0
Net changes in advances with consolidated entities	(25,063)	(92,946)	37,618
Cash paid for financing costs	0	0	0
Net cash used in financing activities	(25,063)	(92,946)	37,618
Effect of exchange rate changes on cash			0
Increase (decrease) in cash and cash equivalents	(174)	(199)	(44)
Cash and cash equivalents	0	174	373	417
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(717)	3,573	4,410
Cash flows from investing activities:
Business acquisitions, net of cash acquired	0	0	0
Capital expenditures	0	0	0
Proceeds from sale of assets	0	0	0
Cash payments to construct assets in connection with future lease transactions	0
Proceeds From Equipment On Lease	0
Cash collected for purchase of interest in accounts receivable	1,258,050	1,226,211	1,011,244
Cash remitted for accounts receivable	(1,262,050)	(1,215,211)	(1,016,244)
Net changes in advances with consolidated entities		0	360
Intercompany loan to affiliate	0
Other	0		0
Net cash used in investing activities	(4,000)	11,000	(4,640)
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution			0
Proceeds from issuance of long-term debt		0	0
Payments on long-term debt	0	0	0
Net additions to (reductions in) short-term borrowings	0	0	0
Net additions to (reductions in) collateralized short-term borrowings	4,000	(11,000)	5,000
Net changes in advances with consolidated entities	729	(3,573)	(4,410)
Cash paid for financing costs	(12)	0	(360)
Net cash used in financing activities	4,717	(14,573)	230
Effect of exchange rate changes on cash			0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents	0	0	0	0
Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(4,000)	11,000	(5,000)
Cash flows from investing activities:
Business acquisitions, net of cash acquired	0	0	0
Capital expenditures	0	0	0
Proceeds from sale of assets	0	0	0
Cash payments to construct assets in connection with future lease transactions	0
Proceeds From Equipment On Lease	0
Cash collected for purchase of interest in accounts receivable	(1,258,050)	(1,226,211)	(1,011,244)
Cash remitted for accounts receivable	1,262,050	1,215,211	1,016,244
Net changes in advances with consolidated entities		(96,514)	33,213
Intercompany loan to affiliate	(24,328)
Other	0		0
Net cash used in investing activities	(20,327)	(107,514)	38,213
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution			0
Proceeds from issuance of long-term debt		0	0
Payments on long-term debt	0	0	0
Net additions to (reductions in) short-term borrowings	0	0	0
Net additions to (reductions in) collateralized short-term borrowings	0	0	0
Net changes in advances with consolidated entities	24,328	96,514	(33,213)
Cash paid for financing costs	0	0	0
Net cash used in financing activities	24,328	96,514	(33,213)
Effect of exchange rate changes on cash			0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents	$ 0	$ 0	$ 0	$ 0