Gain on change in cash flows related to debt during the period.

No definition available.

Name:	gnrc_GainOnChangeInCashFlowsRelatedToDebt
Namespace Prefix:	gnrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents net debt leverage ratio that the borrower has achieved (the borrower's actual net debt leverage ratio is below this target).

+ References

No definition available.

+ Details

Name:	gnrc_NetDebtLeverageRatioAchieved
Namespace Prefix:	gnrc_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold of the ratio used to calculate the financial leverage and the ability to meet financial obligations. If the borrower's actual net debt leverage ratio falls below this threshold for a certain measurement period, the applicable margin related to LIBOR rate loans can be reduced by a specified percentage.

+ References

No definition available.

+ Details

Name:	gnrc_NetDebtLeverageRatioThreshold
Namespace Prefix:	gnrc_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	gnrc_Note8CreditAgreementsDetailsLineItems
Namespace Prefix:	gnrc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to uncommitted incremental term loan facility after amendment.

+ References

No definition available.

+ Details

Name:	gnrc_UncommittedIncrementalTermLoanFacility
Namespace Prefix:	gnrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3044-108585

+ Details

Name:	us-gaap_CashAndCashEquivalentsAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Incremental percentage increase (decrease) in the stated rate on a debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentInterestRateIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),16(a)(1))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13

-Subparagraph 2, 3

-Article 9

+ Details

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

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=gnrc_ABLRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=gnrc_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_ForeignLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=gnrc_NetDebtLeverageRatioThresholdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=gnrc_LIBORFloorRateMember
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Period Type:

- Details

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Note 8 - Credit Agreements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	0 Months Ended	1 Months Ended			3 Months Ended
	Mar. 31, 2015	Apr. 01, 2014	Dec. 31, 2014	Sep. 30, 2014	Apr. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	May 31, 2013
Note 8 - Credit Agreements (Details) [Line Items]
Cash and Cash Equivalents, at Carrying Value	150,085		$ 189,761				$ 173,740	$ 150,147
Short-term Debt	3,103us-gaap_ShortTermBorrowings		5,359us-gaap_ShortTermBorrowings
Net Debt Leverage Ratio Threshold [Member] \| Base Rate [Member] \| Term Loan [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Net Debt Leverage Ratio Threshold [Member] \| Adjusted LIBOR Rate [Member] \| Term Loan [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.50%
Foreign Line of Credit [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Short-term Debt	3,103		5,359
Base Rate [Member] \| Term Loan [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Base Rate [Member] \| ABL Revolving Credit Facility [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Adjusted LIBOR Rate [Member] \| Term Loan [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.75%
Adjusted LIBOR Rate [Member] \| ABL Revolving Credit Facility [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
LIBOR Floor Rate [Member] \| Term Loan [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.75%
Term Loan [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity									1,200,000
Uncommitted Incremental Term Loan Facility									300,000
Net Debt Leverage Ratio Threshold	3.00
Net Debt Leverage Ratio Achieved	3.00	3.00
Debt Instrument, Interest Rate, Increase (Decrease)						0.25%
Gain on Change in Contractual Interest Rate						16,014
Repayments of Long-term Debt	50,000		25,000	50,000	12,000
Write off of Deferred Debt Issuance Cost	1,368		2,084
ABL Revolving Credit Facility [Member]
Note 8 - Credit Agreements (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity									150,000
Long-term Line of Credit	0
Line of Credit Facility, Remaining Borrowing Capacity	148,500