Schedule of Condensed Consolidated Statements of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Change In Accounting Principle
Net income	$ (16,543)	[1],[2],[3]	$ 88,641	[4]	$ 111,387	[5]	$ 33,564	[6]	$ 129,071	[7],[8]	$ 56,706	[9]	$ 87,252	[10]	$ 96,844	[11]	$ 217,049	$ 369,873	$ 384,820
Foreign currency translation reclassification adjustment included in net income																		2,266	(349)
Unrealized gains on marketable securities																	1,307	(3)	1,559
Prior service cost arising during period, net of tax of $0																			3,279
Prior service costs, net of tax of $9 in 2011 and $0 in 2010																	(233)	14	310
Defined benefit pension and post-retirement plans, total																	(233)	14	3,589
Other comprehensive (loss) income																	1,074	2,277	4,799
Comprehensive income																	218,123	372,150	389,619
Originally Reported
Change In Accounting Principle
Net income																		373,809	379,730
Foreign currency translation reclassification adjustment included in net income																		2,266	(349)
Unrealized gains on marketable securities																		(3)	1,559
Actuarial gain (loss) arising during period, net of tax of(3,427) and 3,427 in 2010 and ($1,826) and $1,826 in 2011																		(9,496)	(288)
Prior service cost arising during period, net of tax of $0																			3,279
Actuarial losses, net of tax of $3,385, ($3,385) in 2011 and $133, ($133) in 2010																		5,560	5,378
Prior service costs, net of tax of $9 in 2011 and $0 in 2010																		14	310
Defined benefit pension and post-retirement plans, total																		5,574	5,688
Other comprehensive (loss) income																		(1,659)	9,889
Comprehensive income																		372,150	389,619
Effect Of Accounting Change
Change In Accounting Principle
Net income																		(3,936)	5,090
Actuarial gain (loss) arising during period, net of tax of(3,427) and 3,427 in 2010 and ($1,826) and $1,826 in 2011																		9,496	288
Actuarial losses, net of tax of $3,385, ($3,385) in 2011 and $133, ($133) in 2010																		(5,560)	(5,378)
Defined benefit pension and post-retirement plans, total																		(5,560)	(5,378)
Other comprehensive (loss) income																		3,936	(5,090)
As Adjusted
Change In Accounting Principle
Net income																		369,873	384,820
Foreign currency translation reclassification adjustment included in net income																		2,266	(349)
Unrealized gains on marketable securities																		(3)	1,559
Prior service cost arising during period, net of tax of $0																			3,279
Prior service costs, net of tax of $9 in 2011 and $0 in 2010																		14	310
Defined benefit pension and post-retirement plans, total																		14	310
Other comprehensive (loss) income																		2,277	4,799
Comprehensive income																		$ 372,150	$ 389,619

[1] Restructuring and other, net includes a ($0.4) million fair value adjustment to decrease LitePoint acquisition contingent consideration.

[2] 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.

[3] In the fourth quarter ended December 31, 2012, the change in recognizing pension and postretirement benefit plans expense, as a result of the mark-to-market adjustments, 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.

[4] Restructuring and other, net includes $0.7 million of severance charges related to the headcount reductions of 9 people, of which $0.5 million and 7 people were in Systems Test Group, $0.2 million and 2 people were in Wireless Test.

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

[7] Restructuring and other, net includes $0.5 million of charges related to pension settlement and $3.3 million to the acquisition of LitePoint.

[8] In the fourth quarter ended December 31, 2011, the change in recognizing pension and postretirement benefit plans expense, as a result of the mark-to-market adjustments, decreased gross profit and net income by $2.4 million and $6.1 million, respectively. See Note B: "Accounting Policies" for a discussion of our accounting policy.

[9] Restructuring and other, net includes $1.4 million of charges related to the acquisition of LitePoint.

[10] Restructuring and other, net includes $0.3 million of severance charges related to headcount reductions of approximately 2 people in Semiconductor Test and $0.7 million related to pension settlement charges.

[11] Restructuring and other, net includes $0.8 million of severance charges related to headcount reductions of approximately 5 people in Semiconductor Test and $(0.4) million credit related to early exit of previously impaired leased facilities in Westford and North Reading, Massachusetts.