Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended												12 Months Ended
	Dec. 31, 2013		Sep. 29, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Income tax expense (benefit) from continuing operations, total	$ 13,096,000	[1],[2]	$ 18,093,000	$ 13,801,000	$ (8,015,000)	$ (13,742,000)	[3],[4]	$ 14,384,000	$ 40,605,000	[5]	$ 7,680,000	[6]	$ 36,975,000	$ 48,927,000	$ (129,536,000)
U.S. research and development tax credit reduction Percentage													(7.20%)		(1.10%)
U.S. statutory federal tax rate													35.00%	35.00%	35.00%
Tax savings due to the tax holiday													4,700,000	10,900,000	200,000
Tax savings due to the tax holiday, per share													$ 0.02	$ 0.05	$ 0.00
Accrued interest and penalties	400,000												400,000
Valuation allowance amount decrease/increase													(19,500,000)	4,400,000	(190,200,000)
Valuation allowance includes net deferred tax assets	40,386,000					55,446,000							40,386,000	55,446,000
U.S. Federal operating loss carryforwards	19,354,000												19,354,000
Net operating loss carryforward excess tax deductions related to stock based compensation	0												0
Tax credit carry forwards, approximately	133,400,000												133,400,000
Tax credits carry forwards	65,210,000					64,123,000							65,210,000	64,123,000
Alternative minimum tax credits carryforwards	6,600,000												6,600,000
Unrecognized tax benefits	21,203,000					18,666,000							21,203,000	18,666,000	19,391,000	11,777,000
Unrecognized tax benefits, if recognized would impact effective tax rate	16,000,000												16,000,000
Unrecognized tax benefits, if recognized would impact valuation allowance	5,200,000												5,200,000
Decrease in unrecognized tax benefits													1,000,000
Deferred tax liability not been established	320,000,000												320,000,000
General Business Tax Credit Carryforward
Income Taxes [Line Items]
Tax credits carry forwards	27,700,000												27,700,000
Foreign
Income Taxes [Line Items]
Tax credits carry forwards	34,500,000												34,500,000
State and Local Jurisdiction
Income Taxes [Line Items]
Tax credits carry forwards	64,600,000												64,600,000
Stock Option
Income Taxes [Line Items]
Tax credits carry forwards	41,100,000												41,100,000
GenRad, Inc.
Income Taxes [Line Items]
U.S. Federal operating loss carryforwards	16,500,000												16,500,000
ZTEC Instruments, Inc.
Income Taxes [Line Items]
U.S. Federal operating loss carryforwards	$ 2,800,000												$ 2,800,000
Minimum
Income Taxes [Line Items]
Tax credit carryforward, expiration date													2017
Minimum | Foreign
Income Taxes [Line Items]
Tax credit carryforward, expiration date													2018
Maximum
Income Taxes [Line Items]
Tax credit carryforward, expiration date													2033
Maximum | Foreign
Income Taxes [Line Items]
Tax credit carryforward, expiration date													2022

[1] Interest expense and other includes a $34.2 million gain from the sale of an equity investment.

[2] In the fourth quarter ended December 31, 2013, pension and post retirement net actuarial gains increased gross profit and net income by $2.7 million and $9.1 million, respectively. See Note B: "Accounting Policies" for a discussion of our accounting policy.

[3] In the fourth quarter ended December 31, 2012, we corrected prior period income tax provision (benefit) errors that resulted in a $0.2 million income tax provision. These errors were not individually or in aggregate material to the fourth quarter of 2012 or any prior period.

[4] In the fourth quarter ended December 31, 2012, pension and postretirement actuarial losses decreased gross profit and net income by $8.1 million and $18.3 million, respectively. See Note B: "Accounting Policies" for a discussion of our accounting policy.

[5] Restructuring and other includes $0.3 million of severance charges related to headcount reductions of 10 people in Semiconductor Test and ($6.5) million fair value adjustment to decrease the LitePoint acquisition contingent consideration.

[6] Restructuring and other includes a ($1.8) million fair value adjustment to decrease the LitePoint acquisition contingent consideration.