Consolidated Quarterly Statements of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	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
Quarterly Financial Information [Line Items]
Products	$ 211,710	[1],[2]	$ 365,825	$ 363,087	$ 214,300	$ 179,063	[3],[4]	$ 393,037	$ 480,578	[5]	$ 330,891	[6]	$ 1,154,922		$ 1,383,569		$ 1,160,191
Services	73,591	[1],[2]	67,551	65,802	66,067	69,341	[3],[4]	70,357	67,706	[5]	65,777	[6]	273,011		273,181		268,870
Total net revenues	285,301	[1],[2]	433,376	428,889	280,367	248,404	[3],[4]	463,394	548,284	[5]	396,668	[6]	1,427,933	[7]	1,656,750	[7]	1,429,061	[7]
Cost of products	93,461	[1],[2]	150,365	158,411	96,793	92,599	[3],[4]	169,782	206,498	[5]	174,001	[6]	499,030		642,881		578,936
Cost of services	31,983	[1],[2]	28,717	29,245	30,157	30,400	[3],[4]	33,412	32,280	[5]	31,741	[6]	120,102		127,832		138,302
Total cost of revenues	125,444	[1],[2]	179,082	187,656	126,950	122,999	[3],[4]	203,194	238,778	[5]	205,742	[6]	619,132		770,713		717,238
Gross profit	159,857	[1],[2]	254,294	241,233	153,417	125,405	[3],[4]	260,200	309,506	[5]	190,926	[6]	808,801		886,037		711,823
Engineering and development	64,613	[1],[2]	68,918	67,773	62,751	62,807	[3],[4]	63,946	67,834	[5]	61,279	[6]	264,055		255,866		201,024
Selling and administrative	69,523	[1],[2]	72,917	69,230	67,890	69,289	[3],[4]	69,030	72,064	[5]	66,633	[6]	279,560		277,016		232,093
Acquired intangible assets amortization	18,284	[1],[2]	18,064	18,063	18,036	18,221	[3],[4]	18,429	18,429	[5]	18,429	[6]	72,447		73,508		40,465
Restructuring and other	600	[1],[2]	889	259	332	(317)	[3],[4]	683	(6,262)	[5]	(1,825)	[6]	2,080		(7,721)		6,743
Total operating expenses	153,020	[1],[2]	160,788	155,325	149,009	150,000	[3],[4]	152,088	152,065	[5]	144,516	[6]	618,142		598,669		480,325
Income (loss) from operations	6,837	[1],[2]	93,506	85,908	4,408	(24,595)	[3],[4]	108,112	157,441	[5]	46,410	[6]	190,659		287,368		231,498
Interest income	1,206	[1],[2]	948	903	1,072	1,256	[3],[4]	1,067	874	[5]	893	[6]	4,129		4,090		6,617
Interest expense and other	(27,396)	[1],[2]	6,902	6,454	6,906	6,946	[3],[4]	6,154	6,323	[5]	6,059	[6]
Income (loss) from continuing operations before income taxes	35,439	[1],[2]	87,552	80,357	(1,426)	(30,285)	[3],[4]	103,025	151,992	[5]	41,244	[6]	201,922	[8],[9]	265,976	[8],[9]	214,421	[8],[9]
(Benefit) provision for income taxes	13,096	[1],[2]	18,093	13,801	(8,015)	(13,742)	[3],[4]	14,384	40,605	[5]	7,680	[6]	36,975		48,927		(129,536)
Net income	$ 22,343	[1],[2]	$ 69,459	$ 66,556	$ 6,589	$ (16,543)	[3],[4]	$ 88,641	$ 111,387	[5]	$ 33,564	[6]	$ 164,947		$ 217,049		$ 369,873
Net income (loss) per common share-basic	$ 0.12	[1],[2]	$ 0.36	$ 0.35	$ 0.03	$ (0.09)	[3],[4]	$ 0.47	$ 0.60	[5]	$ 0.18	[6]	$ 0.86		$ 1.16		$ 2.00
Net income (loss) per common share-diluted	$ 0.09	[1],[2]	$ 0.29	$ 0.28	$ 0.03	$ (0.09)	[3],[4]	$ 0.39	$ 0.49	[5]	$ 0.15	[6]	$ 0.70		$ 0.94		$ 1.63

[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.

[7] Revenues attributable to a country are based on location of customer site.

[8] Interest income, interest expense and other, and pension and postretirement plans actuarial gains and losses are included in Corporate and Eliminations.

[9] Included in income (loss) from continuing operations before taxes are charges and credits related to restructuring and other and inventory charges.