Summary of Significant Accounting Policies (Other Intangibles) (Details) (USD $)	12 Months Ended
Dec. 26, 2014	Dec. 27, 2013	Dec. 28, 2012
Finite-Lived Intangible Assets [Line Items]
Cost	$ 161,587,000	$ 137,505,000
Accumulated Amortization	(29,118,000)	(32,255,000)
Foreign Currency Translation	(7,989,000)	1,576,000
Book Value	124,480,000us-gaap_FiniteLivedIntangibleAssetsNet	106,826,000us-gaap_FiniteLivedIntangibleAssetsNet
Not Subject to Amortization
Total Original Cost	216,852,000ggg_OtherIntangibleAssetsGross	177,905,000ggg_OtherIntangibleAssetsGross
Total Book Value	176,278,000us-gaap_OtherIntangibleAssetsNet	147,940,000us-gaap_OtherIntangibleAssetsNet
Current and future amortization expense
Amortization of Intangible Assets	11,600,000us-gaap_AmortizationOfIntangibleAssets	12,500,000us-gaap_AmortizationOfIntangibleAssets	15,000,000us-gaap_AmortizationOfIntangibleAssets
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	12,400,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	12,100,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	11,800,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	11,700,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	11,600,000
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	64,900,000
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	143,144,000	121,205,000
Accumulated Amortization	(21,948,000)	(26,377,000)
Foreign Currency Translation	(7,334,000)	1,458,000
Book Value	113,862,000	96,286,000
Customer Relationships \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (years)	3 years	3 years
Customer Relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (years)	14 years	14 years
Patents, proprietary technology and product documentation
Finite-Lived Intangible Assets [Line Items]
Cost	18,268,000	16,125,000
Accumulated Amortization	(7,126,000)	(5,869,000)
Foreign Currency Translation	(655,000)	118,000
Book Value	10,487,000	10,374,000
Patents, proprietary technology and product documentation \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (years)	3 years	3 years
Patents, proprietary technology and product documentation \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (years)	11 years	11 years
Trademarks, trade names and other
Finite-Lived Intangible Assets [Line Items]
Cost	175,000	175,000
Accumulated Amortization	(44,000)	(9,000)
Foreign Currency Translation	0	0
Book Value	131,000	166,000
Trademarks, trade names and other \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (years)	5 years	5 years
Trademarks, trade names and other \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (years)	5 years	5 years
Trade Names
Not Subject to Amortization
Cost	55,265,000	40,400,000
Foreign Currency Translation	(3,467,000)	714,000
Book Value	$ 51,798,000	$ 41,114,000

Change in other intangible assets from currency translation

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Original cost of assets (excluding financial assets) that lack physical substance, excluding goodwill, having a projected indefinite period of benefit.

+ References

No definition available.

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The gross carrying amount as of the balance sheet date of other indefinite-lived and finite-lived intangible assets that are not separately presented on the statement of financial position.

+ References

No definition available.

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

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

-Publisher FASB

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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Amount of amortization expense expected to be recognized after the fifth fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

No definition available.

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Amount of amortization expense expected to be recognized during the next fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References