Guarantor financial information - Condensed Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 54,550	$ 40,848
Cash flows from investing activities:
Capital expenditures	(10,005)	(25,607)
Proceeds from sale of assets	2,279	3,575
Net cash used in investing activities	(7,726)	(22,046)
Cash flows from financing activities:
Distributions	(50,294)	(51,963)
Proceeds from increase in long-term debt	25,626	21,321
Payments on long-term debt	(2,261)	(4,380)
Net additions to (reductions in) short-term borrowings	(4,467)	20,072
Net additions to collateralized short-term borrowings	10,000	(2,000)
Cash paid for financing costs	(1,390)	(142)
Net cash provided by (used in) financing activities	(39,150)	(17,562)
Increase (decrease) in cash and cash equivalents	7,674	1,240
Cash and cash equivalents - beginning of period	4,965	7,652
Cash and cash equivalents - end of period	12,639	8,892
Ferrellgas, L.P. [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	54,551	42,646
Cash flows from investing activities:
Business acquisitions, net of cash acquired		0
Capital expenditures	(10,005)	(25,607)
Proceeds from sale of assets	2,279	3,575
Cash collected for purchase of interest in accounts receivable	0	0
Cash remitted to Ferrellgas, L.P for accounts receivable	0	0
Intercompany loan to affiliate	0	0
Other		(14)
Net cash used in investing activities	(7,726)	(22,046)
Cash flows from financing activities:
Distributions	(66,658)	(52,493)
Capital contribution		30
Proceeds from increase in long-term debt	25,626	21,321
Payments on long-term debt	(2,261)	(4,380)
Net additions to (reductions in) short-term borrowings	(4,467)	20,072
Net reductions to collateralized short-term borrowings	10,000
Net additions to collateralized short-term borrowings	10,000	(2,000)
Net changes in advances with consolidated entities	0	0
Cash paid for financing costs	(1,390)	(142)
Net cash provided by (used in) financing activities	(39,150)	(17,592)
Effect of exchange rate changes on cash	0	0
Increase (decrease) in cash and cash equivalents	7,675	3,008
Cash and cash equivalents - beginning of period	4,890	5,600
Cash and cash equivalents - end of period	12,565	8,608
Reportable Legal Entities [Member] | Ferrellgas, L.P. (Parent and Co-Issuer) [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	79,220	12,807
Cash flows from investing activities:
Business acquisitions, net of cash acquired		0
Capital expenditures	(10,000)	(14,674)
Proceeds from sale of assets	2,279	1,013
Cash collected for purchase of interest in accounts receivable	0	0
Cash remitted to Ferrellgas, L.P for accounts receivable	0	0
Intercompany loan to affiliate	(14,453)	16,908
Other		(14)
Net cash used in investing activities	(22,174)	3,233
Cash flows from financing activities:
Distributions	(66,658)	(52,493)
Capital contribution		30
Proceeds from increase in long-term debt	25,626	21,321
Payments on long-term debt	(2,261)	(4,380)
Net additions to (reductions in) short-term borrowings	(4,467)	20,072
Net reductions to collateralized short-term borrowings	0
Net additions to collateralized short-term borrowings		0
Net changes in advances with consolidated entities	0	0
Cash paid for financing costs	(1,390)	(142)
Net cash provided by (used in) financing activities	(49,150)	(15,592)
Effect of exchange rate changes on cash	0	2
Increase (decrease) in cash and cash equivalents	7,896	450
Cash and cash equivalents - beginning of period	4,472	5,579
Cash and cash equivalents - end of period	12,368	6,029
Reportable Legal Entities [Member] | Ferrellgas Finance Corp. (Co-Issuer) [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(2)	(3)
Cash flows from investing activities:
Business acquisitions, net of cash acquired		0
Capital expenditures	0	0
Proceeds from sale of assets	0	0
Cash collected for purchase of interest in accounts receivable	0	0
Cash remitted to Ferrellgas, L.P for accounts receivable	0	0
Intercompany loan to affiliate	0	0
Other		0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Distributions	0	0
Capital contribution		0
Proceeds from increase in long-term debt	0	0
Payments on long-term debt	0	0
Net additions to (reductions in) short-term borrowings	0	0
Net reductions to collateralized short-term borrowings	0
Net additions to collateralized short-term borrowings		0
Net changes in advances with consolidated entities	2	3
Cash paid for financing costs	0	0
Net cash provided by (used in) financing activities	2	3
Effect of exchange rate changes on cash	0	0
Increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	1	1
Cash and cash equivalents - end of period	1	1
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(15,354)	22,041
Cash flows from investing activities:
Business acquisitions, net of cash acquired		0
Capital expenditures	(5)	(10,933)
Proceeds from sale of assets	0	2,562
Cash collected for purchase of interest in accounts receivable	0	0
Cash remitted to Ferrellgas, L.P for accounts receivable	0	0
Intercompany loan to affiliate	0	0
Other		0
Net cash used in investing activities	(5)	(8,371)
Cash flows from financing activities:
Distributions	0	0
Capital contribution		0
Proceeds from increase in long-term debt	0	0
Payments on long-term debt	0	0
Net additions to (reductions in) short-term borrowings	0	0
Net reductions to collateralized short-term borrowings	0
Net additions to collateralized short-term borrowings		0
Net changes in advances with consolidated entities	15,138	(11,112)
Cash paid for financing costs	0	0
Net cash provided by (used in) financing activities	15,138	(11,112)
Effect of exchange rate changes on cash	0	0
Increase (decrease) in cash and cash equivalents	(221)	2,558
Cash and cash equivalents - beginning of period	417	20
Cash and cash equivalents - end of period	196	2,578
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	687	5,801
Cash flows from investing activities:
Business acquisitions, net of cash acquired		0
Capital expenditures	0	0
Proceeds from sale of assets	0	0
Cash collected for purchase of interest in accounts receivable	183,939	186,280
Cash remitted to Ferrellgas, L.P for accounts receivable	(193,939)	(184,280)
Intercompany loan to affiliate	0	0
Other		0
Net cash used in investing activities	(10,000)	2,000
Cash flows from financing activities:
Distributions	0	0
Capital contribution		0
Proceeds from increase in long-term debt	0	0
Payments on long-term debt	0	0
Net additions to (reductions in) short-term borrowings	0	0
Net reductions to collateralized short-term borrowings	10,000
Net additions to collateralized short-term borrowings		(2,000)
Net changes in advances with consolidated entities	(687)	(5,799)
Cash paid for financing costs	0	0
Net cash provided by (used in) financing activities	9,313	(7,799)
Effect of exchange rate changes on cash	0	(2)
Increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0
Cash and cash equivalents - end of period	0	0
Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(10,000)	2,000
Cash flows from investing activities:
Business acquisitions, net of cash acquired		0
Capital expenditures	0	0
Proceeds from sale of assets	0	0
Cash collected for purchase of interest in accounts receivable	(183,939)	(186,280)
Cash remitted to Ferrellgas, L.P for accounts receivable	193,939	184,280
Intercompany loan to affiliate	14,453	(16,908)
Other		0
Net cash used in investing activities	24,453	(18,908)
Cash flows from financing activities:
Distributions	0	0
Capital contribution		0
Proceeds from increase in long-term debt	0	0
Payments on long-term debt	0	0
Net additions to (reductions in) short-term borrowings	0	0
Net reductions to collateralized short-term borrowings	0
Net additions to collateralized short-term borrowings		0
Net changes in advances with consolidated entities	(14,453)	16,908
Cash paid for financing costs	0	0
Net cash provided by (used in) financing activities	(14,453)	16,908
Effect of exchange rate changes on cash	0	0
Increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0
Cash and cash equivalents - end of period	$ 0	$ 0