Employee Retirement and Other Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Components of other comprehensive income, net of tax [Roll Forward]
Foreign currency effect, net of tax	$ (2,735,000)		$ (10,368,000)	$ 5,149,000
Ceradyne SMART 401(k) Plan [Member]
Supplemental Retirement Plan [Abstract]
Defined contribution plan, description	In December 1988, the Board of Directors of the Company approved the adoption of a supplemental retirement plan, the Ceradyne SMART 401(k) Plan (the Plan), in which substantially all employees are eligible to participate after completing 90 days of employment. Participation in the Plan is voluntary. An employee may elect to contribute up to the maximum deferred tax amount of $16,500 in 2011 as a basic contribution. The Company may contribute any amount which the Board of Directors annually determines appropriate. Company contributions fully vest and are non-forfeitable after the participant has completed five years of service.
Maximum amount of annual deferred tax contribution per employee	16,500
Company contributions	1,500,000		1,300,000	1,500,000
German Pension and Benefit Plans [Member]
German Pension and Benefit Plans [Abstract]
Number of pension and benefit plans	4
Estimated future employer contributions in next fiscal year [Abstract]
Total contributions expected in 2012	3,328,000
Pensionskasse - Old [Member]
Estimated future employer contributions in next fiscal year [Abstract]
Total contributions expected in 2012	1,744,000
Pensionskasse - New [Member]
Pensionskasse - New [Abstract]
Percentage of annual contributions per employee (in hundredths)	2.00%
Total costs	207,603		130,173	134,346
Additional Compensation Plan [Member]
Estimated future employer contributions in next fiscal year [Abstract]
Total contributions expected in 2012	1,370,000
Deferred Compensation Plan [Member]
Estimated future employer contributions in next fiscal year [Abstract]
Total contributions expected in 2012	214,000
Additional and Deferred Compensation Plans [Member]
Components of net periodic benefit costs [Abstract]
Service cost	757,000		675,000	592,000
Interest cost	850,000		727,000	681,000
Amortization of actuarial loss	229,000		164,000	88,000
Net periodic benefit cost	1,836,000		1,566,000	1,361,000
Weighted-average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate (in hundredths)	5.10%		5.40%	6.25%
Rate of long-term compensation increase (in hundredths)	3.00%		3.00%	3.00%
Weighted-average assumptions used to determine pension benefit obligations [Abstract]
Discount rate (in hundredths)	4.60%		5.10%
Rate of long-term compensation increase (in hundredths)	3.00%		3.00%
Funded status at end of year:
Projected benefit obligation	(18,323,000)		(16,109,000)	(14,657,000)
Assets at fair value	0		0
Funded status	(18,323,000)		(16,109,000)
Net amounts recognized in consolidated balance sheet:
Current liabilities	(275,000)		(238,000)
Non-current liabilities	(18,048,000)		(15,871,000)
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	(16,109,000)		(14,657,000)
Foreign currency exchange rate changes	712,000		944,000
Service costs	(757,000)		(675,000)	(592,000)
Interest costs	(850,000)		(727,000)	(681,000)
Actuarial gains (losses)	(1,495,000)		(1,146,000)
Benefits paid	176,000		152,000
Projected benefit obligation at end of year	(18,323,000)		(16,109,000)	(14,657,000)
Accumulated benefit obligation	(16,656,000)		(14,576,000)
Change in fair value of plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Benefits paid	(176,000)		(152,000)
Fair value of plan assets at end of year	0		0
Components of other comprehensive income, before tax [Roll Forward]
Accumulated other comprehensive (loss) income, before tax, at beginning of year	(4,938,000)		(3,956,000)
Net actuarial (loss) gain arising during current year, before tax	(1,495,000)		(1,146,000)
Amortization of actuarial loss, before tax	229,000		163,000
Foreign currency effect, before tax	71,000		1,000
Accumulated other comprehensive (loss) income, before tax, at end of year	(6,133,000)	[1]	(4,938,000)	(3,956,000)
Components of other comprehensive income, tax (expense) benefit [Roll Forward]
Accumulated other comprehensive (loss) income, tax, at beginning of year	1,448,000		1,160,000
Net actuarial (loss) gain arising during current year, tax	440,000		336,000
Amortization of actuarial loss, tax	(67,000)		(48,000)
Foreign currency effect, tax	(21,000)		0
Accumulated other comprehensive (loss) income, tax, at end of year	1,800,000	[1]	1,448,000	1,160,000
Components of other comprehensive income, net of tax [Roll Forward]
Accumulated other comprehensive (loss) income, net of tax, at beginning of year	(3,490,000)		(2,796,000)
Net actuarial (loss) gain arising during current year, net of tax	(1,055,000)		(810,000)
Amortization of actuarial loss, net of tax	162,000		115,000
Foreign currency effect, net of tax	50,000		1,000
Accumulated other comprehensive (loss) income, net of tax, at end of year	(4,333,000)	[1]	(3,490,000)	(2,796,000)
Net actuarial loss included in accumulated other comprehensive loss that will be amortized into income over next fiscal year	276,000
Estimated future benefit payments [Abstract]
2012	274,000
2013	303,000
2014	369,000
2015	412,000
2016	459,000
2017 - 2021	3,667,000
Ceradyne Boron Products Pension Plans [Member]
Components of net periodic benefit costs [Abstract]
Service cost	8,000		63,000	86,000
Interest cost	478,000		506,000	513,000
Amortization of actuarial loss	116,000		146,000	202,000
Expected return on assets	(556,000)		(520,000)	(490,000)
Net periodic benefit cost	46,000		195,000	311,000
Weighted-average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate (in hundredths)	5.28%		5.75%	5.74%
Rate of long-term compensation increase (in hundredths)	3.00%		3.00%	4.00%
Expected return on plan assets (in hundredths)	8.00%		8.00%	8.00%
Weighted-average assumptions used to determine pension benefit obligations [Abstract]
Discount rate (in hundredths)	4.39%		5.28%
Rate of long-term compensation increase (in hundredths)	3.00%		3.00%
Funded status at end of year:
Projected benefit obligation	(10,425,000)		(9,599,000)	(9,088,000)
Assets at fair value	7,150,000		7,125,000	6,857,000
Funded status	(3,275,000)		(2,474,000)
Net amounts recognized in consolidated balance sheet:
Non-current liabilities	(3,275,000)		(2,474,000)
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	(9,599,000)		(9,088,000)
Service costs	(8,000)		(63,000)	(86,000)
Interest costs	(478,000)		(506,000)	(513,000)
Actuarial gains (losses)	(909,000)		(521,000)
Benefits paid	569,000		579,000
Projected benefit obligation at end of year	(10,425,000)		(9,599,000)	(9,088,000)
Change in fair value of plan assets [Roll Forward]
Fair value of plan assets at beginning of year	7,125,000		6,857,000
Actual return on plan assets	123,000		749,000
Employer contributions	471,000		98,000
Benefits paid	(569,000)		(579,000)
Fair value of plan assets at end of year	7,150,000		7,125,000	6,857,000
Components of other comprehensive income, before tax [Roll Forward]
Accumulated other comprehensive (loss) income, before tax, at beginning of year	(2,217,000)		(2,072,000)
Net actuarial (loss) gain arising during current year, before tax	(1,125,000)		(145,000)
Accumulated other comprehensive (loss) income, before tax, at end of year	(3,442,000)	[2]	(2,217,000)	(2,072,000)
Components of other comprehensive income, tax (expense) benefit [Roll Forward]
Accumulated other comprehensive (loss) income, tax, at beginning of year	864,000		807,000
Net actuarial (loss) gain arising during current year, tax	478,000		57,000
Accumulated other comprehensive (loss) income, tax, at end of year	1,342,000	[2]	864,000	807,000
Components of other comprehensive income, net of tax [Roll Forward]
Accumulated other comprehensive (loss) income, net of tax, at beginning of year	(1,353,000)		(1,265,000)
Net actuarial (loss) gain arising during current year, net of tax	(747,000)		(88,000)
Accumulated other comprehensive (loss) income, net of tax, at end of year	(2,100,000)	[2]	(1,353,000)	(1,265,000)
Net actuarial loss included in accumulated other comprehensive loss that will be amortized into income over next fiscal year	236,000
Estimated future benefit payments [Abstract]
2012	587,000
2013	644,000
2014	627,000
2015	618,000
2016	635,000
2017 - 2021	3,371,000
Pension plan with accumulated benefit obligations in excess of fair value of plan assets [Abstract]
Fair value of plan assets at end of year	7,150,000		7,125,000
Accumulated benefit obligation at end of year	(10,425,000)		(9,596,000)
Ceradyne Boron Products Pension Plans [Member] | Investment fund - equity securities [Member]
Pension plan with accumulated benefit obligations in excess of fair value of plan assets [Abstract]
Fair value of plan assets at end of year	4,622,000		4,618,000
Target plan asset allocations (in hundredths)	65.00%
Ceradyne Boron Products Pension Plans [Member] | Investment fund - fixed income securities [Member]
Pension plan with accumulated benefit obligations in excess of fair value of plan assets [Abstract]
Fair value of plan assets at end of year	$ 2,528,000		$ 2,507,000
Target plan asset allocations (in hundredths)	25.00%
Ceradyne Boron Products Pension Plans [Member] | Other Investment [Member]
Pension plan with accumulated benefit obligations in excess of fair value of plan assets [Abstract]
Target plan asset allocations (in hundredths)	10.00%

[1] Approximately $276 of net actuarial loss included in accumulated other comprehensive loss will be amortized into income in 2012.

[2] Approximately $236 of actuarial net loss included in accumulated other comprehensive loss will be amortized into income in 2012.