Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Line Items]
Income tax expense (benefit) from continuing operations, total	$ 48,927,000	$ (129,536,000)	$ 16,655,000
Valuation allowance includes net deferred tax assets	55,400,000	51,100,000
Valuation allowance amount decreased	4,400,000	190,200,000	60,000,000
U.S. Federal Operating Loss Carryforwards	22,354,000
Net operating loss carryforward excess tax deductions related to stock based compensation	0
Tax credit carry forwards, approximately	119,000,000
Tax credits carry forwards	64,123,000	76,248,000
Alternative minimum tax credits carryforwards	6,600,000
Tax savings due to the tax holiday	10,900,000	200,000	0
Tax savings due to the tax holiday, per share	$ 0.05	$ 0.00	$ 0.00
Unrecognized tax benefits	17,467,000	19,678,000	12,028,000	12,767,000
Unrecognized tax benefits, if recognized would impact effective tax rate	14,800,000
Unrecognized tax benefits, if recognized would impact valuation allowance	2,700,000
Decrease in unrecognized tax benefits	300,000
Deferred tax liability not been established	10,600,000
General Business Tax Credit Carryforward
Income Taxes [Line Items]
Tax credits carry forwards	15,500,000
Foreign Country
Income Taxes [Line Items]
Tax credits carry forwards	42,500,000
State and Local Jurisdiction
Income Taxes [Line Items]
Tax credits carry forwards	54,400,000
American Taxpayer Relief Act of Twenty Twelve
Income Taxes [Line Items]
Unrecognized tax benefits	7,000,000
GenRad, Inc.
Income Taxes [Line Items]
U.S. Federal Operating Loss Carryforwards	$ 22,400,000
Minimum
Income Taxes [Line Items]
Tax credit carryforward, expiration date	2028
Foreign tax carryforward, expiration date	2013
Maximum
Income Taxes [Line Items]
Tax credit carryforward, expiration date	2031
Foreign tax carryforward, expiration date	2022