Pension and Other Post-retirement Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
German Pension and Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of pension and benefit plans	4
Ceradyne Boron Products Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of pension and benefit plans	2
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit costs [Abstract]
Service cost	$ 192	$ 192
Interest cost	332	332
Expected return on plan assets	(139)	(139)
Amortization of unrecognized (gain) loss	(10)	(10)
Net periodic benefit cost	$ 375	$ 375