Consolidated Balance Sheets Parenthetical (USD $) In Thousands, unless otherwise specified	Jun. 29, 2012	Dec. 30, 2011
Statement Of Financial Position Parenthetical [Abstract]
Receivables allowances	$ 5,900	$ 5,500

Allowances for doubtful accounts, returns and credits. This includes allowances for accounts that are due to the Company within one year and are deemed uncollectable and allowances for sales returns and other credits.

No definition available.

Name:	ggg_AllowancesForDoubtfulAccountsAndSales
Namespace Prefix:	ggg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant