Guarantor financial information Condensed Consolidated Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 127,288	$ 194,327	$ 203,072
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	(3,539)	(15,144)	(641,427)
Payments to Acquire Productive Assets	(50,472)	(117,518)	(72,481)
Proceeds from sale of assets	8,510	17,089	5,905
Other	(37)	(286)	(14)
Net cash used in investing activities	(45,538)	(115,859)	(708,017)
Cash flows from financing activities:
Distributions	(79,733)	(204,160)	(167,105)
Prepaid expenses and other current assets	33,388	39,973
Inventories	92,552	90,594
Proceeds from increase in long-term debt	230,864	168,117	628,134
Repayments of Long-term Debt	(174,292)	(14,959)	(119,457)
Proceeds from (Repayments of) Short-term Debt	(41,510)	25,972	5,800
Net additions to collateralized short-term borrowings	(5,000)	(6,000)	(21,000)
Cash paid for financing costs	(6,078)	(1,214)	(10,301)
Net cash provided by (used in) financing activities	(80,955)	(81,155)	504,310
Effect of exchange rate changes on cash	0	0	(2)
Increase (decrease) in cash and cash equivalents	795	(2,687)	(637)
Cash and cash equivalents	5,760	4,965	7,652	$ 8,289
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(21,460)	(18,387)	(13,416)
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	0	0	562,500
Net cash used in investing activities	(47,319)	266,818	(2,988)
Cash flows from financing activities:
Distributions	79,733	204,160	167,105
Prepaid expenses and other current assets	4	18
Proceeds from increase in long-term debt	168,000
Cash paid for financing costs	3,653	0	0
Net cash provided by (used in) financing activities	68,763	(250,408)	18,450
Increase (decrease) in cash and cash equivalents	(16)	(1,977)	2,046
Cash and cash equivalents	59	75	2,052	6
Ferrellgas, L.P. [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	148,748	212,744	216,488
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	(3,539)	(15,144)	(78,927)
Payments to Acquire Productive Assets	(50,472)	(117,518)	(72,481)
Proceeds from sale of assets	8,510	17,089	5,905
Proceeds from (Repayments of) Accounts Receivable Securitization	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization, Related Party	0	0	0
Proceeds from Collection of (Payments to Fund) Long-term Loans to Related Parties	0	0	0
Other	(37)	(286)	(14)
Net cash used in investing activities	(45,538)	(115,859)	(145,517)
Cash flows from financing activities:
Distributions	(119,879)	(269,541)	(607,875)
Capital contribution	167,843	30	51,047
Prepaid expenses and other current assets	33,426	39,955
Inventories	92,552	90,594
Proceeds from increase in long-term debt	62,864	168,117	628,134
Repayments of Long-term Debt	(174,292)	(14,959)	(119,457)
Proceeds from (Repayments of) Short-term Debt	(41,510)	25,972	5,800
Net additions to collateralized short-term borrowings	5,000	(6,000)	(21,000)
Advances (To) From Related Parties	0	0	0
Cash paid for financing costs	(2,425)	(1,214)	(10,301)
Net cash provided by (used in) financing activities	(102,399)	(97,595)	(73,652)
Effect of exchange rate changes on cash	0	0	(2)
Increase (decrease) in cash and cash equivalents	811	(710)	(2,683)
Cash and cash equivalents	5,701	4,890	5,600	8,283
Reportable Legal Entities [Member] | Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	185,640	102,569	197,740
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	(3,539)	(15,144)	(71,750)
Payments to Acquire Productive Assets	(49,107)	(52,501)	(56,955)
Proceeds from sale of assets	8,510	17,089	5,905
Proceeds from (Repayments of) Accounts Receivable Securitization	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization, Related Party	0	0	0
Proceeds from Collection of (Payments to Fund) Long-term Loans to Related Parties	(33,573)	38,759	(24,493)
Other	(37)	(286)	(14)
Net cash used in investing activities	(77,746)	(12,083)	(147,307)
Cash flows from financing activities:
Distributions	(119,879)	(269,541)	(607,875)
Capital contribution	167,843	30	51,047
Prepaid expenses and other current assets	26,106	27,922
Inventories	78,963	71,422
Proceeds from increase in long-term debt	62,864	168,117	628,134
Repayments of Long-term Debt	(174,292)	(14,959)	(119,457)
Proceeds from (Repayments of) Short-term Debt	(41,510)	25,972	5,800
Net additions to collateralized short-term borrowings	0	0	0
Advances (To) From Related Parties	0	0	0
Cash paid for financing costs	(2,065)	(1,214)	(10,301)
Net cash provided by (used in) financing activities	(107,039)	(91,595)	(52,652)
Effect of exchange rate changes on cash		2	0
Increase (decrease) in cash and cash equivalents	855	(1,107)	(2,219)
Cash and cash equivalents	5,327	4,472	5,579	7,798
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(36,297)	89,728	(12,875)
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	0	0	(7,177)
Payments to Acquire Productive Assets	(1,365)	(65,017)	(15,526)
Proceeds from sale of assets	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization, Related Party	0	0	0
Proceeds from Collection of (Payments to Fund) Long-term Loans to Related Parties	0	0	0
Other	0	0	0
Net cash used in investing activities	(1,365)	(65,017)	(22,703)
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution	0	0	0
Prepaid expenses and other current assets	7,314	12,029
Inventories	13,589	19,172
Proceeds from increase in long-term debt	0	0	0
Repayments of Long-term Debt	0	0	0
Proceeds from (Repayments of) Short-term Debt	0	0	0
Net additions to collateralized short-term borrowings	0	0	0
Advances (To) From Related Parties	37,618	(24,314)	35,114
Cash paid for financing costs	0	0	0
Net cash provided by (used in) financing activities	37,618	(24,314)	35,114
Effect of exchange rate changes on cash		0	0
Increase (decrease) in cash and cash equivalents	(44)	397	(464)
Cash and cash equivalents	373	417	20	484
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	4,410	14,456	10,627
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	0	0	0
Payments to Acquire Productive Assets	0	0	0
Proceeds from sale of assets	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization	1,011,244	946,804	1,299,325
Proceeds from (Repayments of) Accounts Receivable Securitization, Related Party	(1,016,244)	(940,804)	(1,278,325)
Proceeds from Collection of (Payments to Fund) Long-term Loans to Related Parties	360	0	0
Other	0	0	0
Net cash used in investing activities	(4,640)	6,000	21,000
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution	0	0	0
Prepaid expenses and other current assets	6	2
Inventories	0	0
Proceeds from increase in long-term debt	0	0	0
Repayments of Long-term Debt	0	0	0
Proceeds from (Repayments of) Short-term Debt	0	0	0
Net additions to collateralized short-term borrowings	5,000	(6,000)	(21,000)
Advances (To) From Related Parties	(4,410)	(14,454)	(10,625)
Cash paid for financing costs	(360)	0	0
Net cash provided by (used in) financing activities	230	(20,454)	(31,625)
Effect of exchange rate changes on cash		(2)	(2)
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents	0	0	0	0
Reportable Legal Entities [Member] | Co-issuer [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(5)	(9)	(4)
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	0	0	0
Payments to Acquire Productive Assets	0	0	0
Proceeds from sale of assets	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization, Related Party	0	0	0
Proceeds from Collection of (Payments to Fund) Long-term Loans to Related Parties	0	0	0
Other	0	0	0
Net cash used in investing activities	0	0	0
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution	0	0	0
Prepaid expenses and other current assets	0	2
Inventories	0	0
Proceeds from increase in long-term debt	0	0	0
Repayments of Long-term Debt	0	0	0
Proceeds from (Repayments of) Short-term Debt	0	0	0
Net additions to collateralized short-term borrowings	0	0	0
Advances (To) From Related Parties	5	9	4
Cash paid for financing costs	0	0	0
Net cash provided by (used in) financing activities	5	9	4
Effect of exchange rate changes on cash		0	0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents	1	1	1	1
Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(5,000)	6,000	21,000
Cash flows from investing activities:
Payments to Acquire Businesses, Net of Cash Acquired	0	0	0
Payments to Acquire Productive Assets	0	0	0
Proceeds from sale of assets	0	0	0
Proceeds from (Repayments of) Accounts Receivable Securitization	(1,011,244)	(946,804)	(1,299,325)
Proceeds from (Repayments of) Accounts Receivable Securitization, Related Party	1,016,244	940,804	1,278,325
Proceeds from Collection of (Payments to Fund) Long-term Loans to Related Parties	33,213	(38,759)	24,493
Other	0	0	0
Net cash used in investing activities	38,213	(44,759)	3,493
Cash flows from financing activities:
Distributions	0	0	0
Capital contribution	0	0	0
Prepaid expenses and other current assets	0	0
Inventories	0	0
Proceeds from increase in long-term debt	0	0	0
Repayments of Long-term Debt	0	0	0
Proceeds from (Repayments of) Short-term Debt	0	0	0
Net additions to collateralized short-term borrowings	0	0	0
Advances (To) From Related Parties	(33,213)	38,759	(24,493)
Cash paid for financing costs	0	0	0
Net cash provided by (used in) financing activities	(33,213)	38,759	(24,493)
Effect of exchange rate changes on cash		0	0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents	$ 0	$ 0	$ 0	$ 0