Derivative Instruments and Hedging Activities (Changes in Derivative Value Effect on Other Comprehensive Income Loss) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jul. 31, 2017	Jul. 31, 2016
Beginning balance	$ 24,332		$ 24,332		$ 14,601
Change in value of risk management derivatives	1,072	$ 15,262	23,521	$ 20,400
Reclassification of gains and losses on commodity hedges to cost of product sold - propane and other gas liquids sales	(9,743)	514	(13,692)	4,752
Ending balance	24,332		24,332
Ferrellgas, L.P. [Member]
Beginning balance	24,593		24,593		14,764
Change in value of risk management derivatives	1,072	15,262	23,521	20,400
Reclassification of gains and losses on commodity hedges to cost of product sold - propane and other gas liquids sales	(9,743)	514	(13,692)	4,752
Ending balance	24,593		24,593
Propane commodity derivatives [Member]
Change in value of risk management derivatives	960	14,699	23,283	19,572
Reclassification of gains and losses on commodity hedges to cost of product sold - propane and other gas liquids sales			(14,018)	3,523
Propane commodity derivatives [Member] \| Ferrellgas, L.P. [Member]
Change in value of risk management derivatives	960	14,699	23,283	19,572
Reclassification of gains and losses on commodity hedges to cost of product sold - propane and other gas liquids sales			(14,018)	3,523
Interest Rate Swap [Member]
Change in value of risk management derivatives	112	563	238	828
Derivative, Net Hedge Ineffectiveness Gain (Loss)			326	1,229
Interest Rate Swap [Member] \| Ferrellgas, L.P. [Member]
Change in value of risk management derivatives	112	563	238	828
Derivative, Net Hedge Ineffectiveness Gain (Loss)			326	1,229
Derivative [Member]
Beginning balance	24,477	15,337	24,477	15,337	14,648	$ (9,815)
Ending balance	24,477	15,337	24,477	15,337
Derivative [Member] \| Ferrellgas, L.P. [Member]
Beginning balance	24,477	15,337	24,477	15,337	$ 14,648	$ (9,815)
Ending balance	$ 24,477	$ 15,337	$ 24,477	$ 15,337

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e681-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

+ Details

Name:	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) from the ineffectiveness of the hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

+ Details

Name:	us-gaap_DerivativeNetHedgeIneffectivenessGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=fgp_FerrellgasLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_EnergyRelatedDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_DerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: