Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011	Feb. 05, 2012	Jun. 30, 2011
Document and Entity Information [Abstract]
Entity Registrant Name	CERADYNE INC
Entity Central Index Key	0000018937
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 910,100,000.00
Entity Common Stock, Shares Outstanding		24,194,539.00
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	true
Amendment Description	Ceradyne, Inc. (the “Company”) is filing this Amendment No. 1 to its Form 10-K for the year ended December 31, 2011 (the “Report”) for the purpose of including Interactive Data Files (Exhibit 101) formatted in XBRL (Extensible Business Reporting Language) with detail tagging of the notes to the consolidated financial statements. Previously, the Company included in the Report Interactive Data Files formatted in XBRL with the notes to the consolidated financial statement in block-tagged form. We have also unchecked the box on the cover page regarding disclosure of delinquent filers pursuant to Item 405 of Regulation S-K, as the disclosure of one delinquent filing was included in our definitive proxy statement for our annual meeting of stockholders to be held on May 16, 2012, which proxy statement is incorporated by reference into Part III of the Report. No revisions have been made with respect to any other disclosures contained in the Report.
Document Period End Date	Dec. 31, 2011