Fair value derivative contracts excluding impact of credit risk.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Date the derivative contract become effective, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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- Details

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Balance Type:	na
Period Type:	duration

- Definition

Number of new contracts entered into during the period mentioned.

+ References

No definition available.

+ Details

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Namespace Prefix:	gnrc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Floor rate on an interest rate derivative such as an interest rate floor or collar. If market rates falls below the floor rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a),(c),(d),(e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

+ Details

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

- Definition

High end period remaining until maturity for the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the entity entered into the derivative contract, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the derivative contract matures, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5579245-113959

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Note 4 - Derivative Instruments and Hedging Activities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May 19, 2014	Oct. 23, 2013	May 30, 2012
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Fair value of derivative contracts excluding impact of credit risk	$ (1,727)	$ 1,385
Cost of Sales [Member] \| Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(629)	(605)	386
Commodity Contract [Member] \| Maximum [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Higher Remaining Maturity Range	18 months
Foreign Exchange Contract [Member] \| Maximum [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Higher Remaining Maturity Range	12 months
Foreign Exchange Contract [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(149)	(56)
Derivative, Number of Instruments Held			0
Interest Rate Swap [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Number of Instruments Held						4
Number of New Contracts Entered				1	2
Interest Rate Swap Five [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Floor Interest Rate	0.75%
Interest Rate Swap Five [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Inception Date	Oct. 23, 2013
Derivative Effective Date	Jul. 01, 2014
Derivative, Maturity Date	Jul. 01, 2018
Derivative, Notional Amount	100,000
Derivative, Fixed Interest Rate	1.737%
Interest Rate Swap Six [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Floor Interest Rate	0.75%
Interest Rate Swap Six [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Inception Date	Oct. 23, 2013
Derivative Effective Date	Jul. 01, 2014
Derivative, Maturity Date	Jul. 01, 2018
Derivative, Notional Amount	100,000
Derivative, Fixed Interest Rate	1.742%
Interest Rate Swap Seven [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Floor Interest Rate	0.75%
Interest Rate Swap Seven [Member]
Note 4 - Derivative Instruments and Hedging Activities (Details) [Line Items]
Derivative, Inception Date	May 19, 2014
Derivative Effective Date	Jul. 01, 2014
Derivative, Maturity Date	Jul. 01, 2018
Derivative, Notional Amount	$ 100,000
Derivative, Fixed Interest Rate	1.6195%