XML 35 R25.htm IDEA: XBRL DOCUMENT v3.20.2

Inventories - Additional Information (Detail) - USD ($)	9 Months Ended
	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Inventory [Line Items]
Slow moving and obsolete inventory reserve	$ 4,569,000	$ 4,700,000
Cumulative impact of change in accounting method inventory	$ 148,053,000	$ 141,897,000
Three to Four Years Old Inventory [Member]
Inventory [Line Items]
Cost basis reduction in inventory, percentage	50.00%
Inventory, minimum time period on the shelf, years	3 years
Inventory, maximum time period on the shelf, years	4 years
Four to Five Years Old Inventory [Member]
Inventory [Line Items]
Cost basis reduction in inventory, percentage	75.00%
Inventory, minimum time period on the shelf, years	4 years
Inventory, maximum time period on the shelf, years	5 years
Greater Than Five Years Old Inventory [Member]
Inventory [Line Items]
Inventory, minimum time period on the shelf, years	5 years
Inventory valuation estimate	$ 0
Provisions on obsolescence	$ 0
Inventory Valuation Adjustment [Member]
Inventory [Line Items]
Cumulative impact of change in accounting method inventory			$ 2,708,000

X

- Definition

Represents the percentage cost basis reduction for inventories related to obsolescence, excessive levels, deterioration, possible alternative uses and other factors in determining net realizable value. Inventories are valued at the lower of cost or market, with cost being determined principally by using the last-in, first-out (LIFO) method and market defined as replacement cost for raw materials and net realizable value for work in process and finished goods. Appropriate consideration is given to obsolescence, excessive levels, deterioration, possible alternative uses and other factors in determining net realizable value. The cost of work in process and finished goods includes materials, direct labor, variable costs and overhead. The Company evaluates the need to record inventory adjustments on all inventories, including raw material, work in process, finished goods, spare parts and used equipment. Used equipment acquired by the Company on trade-in from customers is carried at estimate

+ References

No definition available.

+ Details

Name:	genc_CostBasisReductionInInventoryPercentage
Namespace Prefix:	genc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Inventory cost basis determination period maximum.

+ References

No definition available.

+ Details

Name:	genc_InventoryCostBasisDeterminationPeriodMaximum
Namespace Prefix:	genc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Inventory cost basis determination period minimum.

+ References

No definition available.

+ Details

Name:	genc_InventoryCostBasisDeterminationPeriodMinimum
Namespace Prefix:	genc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Represents the inventory valuation estimate amount after accounting for inventories related to obsolescence, excessive levels, deterioration, possible alternative uses and other factors in determining net realizable value. Inventories are valued at the lower of cost or market, with cost being determined principally by using the last-in, first-out (LIFO) method and market defined as replacement cost for raw materials and net realizable value for work in process and finished goods. Appropriate consideration is given to obsolescence, excessive levels, deterioration, possible alternative uses and other factors in determining net realizable value. The cost of work in process and finished goods includes materials, direct labor, variable costs and overhead. The Company evaluates the need to record inventory adjustments on all inventories, including raw material, work in process, finished goods, spare parts and used equipment. Used equipment acquired by the Company on trade-in from customers i

+ References

No definition available.

+ Details

Name:	genc_InventoryValuationEstimate
Namespace Prefix:	genc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(c))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_InventoryLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116847112&loc=d3e4542-108314

+ Details

Name:	us-gaap_InventoryWriteDown
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30)(a)(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(a)(4))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(i)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

+ Details

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

X

- Details

Name:	us-gaap_PublicUtilitiesInventoryAxis=genc_MoreThanThreeAndWithinFourYearFromBalanceSheetDateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PublicUtilitiesInventoryAxis=genc_MoreThanFourAndWithinFiveYearFromBalanceSheetDateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PublicUtilitiesInventoryAxis=genc_MoreThanFiveYearFromBalanceSheetDateAndThereafterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_AdjustmentsForChangeInAccountingPrincipleAxis=genc_InventoryValuationAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: