Consolidated Quarterly Statements of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																	12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019	Sep. 29, 2019	[3]	Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jul. 01, 2018		Apr. 01, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information [Line Items]
Total revenues	$ 654,650	[1],[2]		$ 582,038		$ 564,178	[4]	$ 494,099	[5]	$ 519,558	[6],[7]	$ 566,848	[8]	$ 526,929	[9]	$ 487,467	[10]
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	271,412	[1],[2]		237,000		240,260	[4]	206,464	[5]	210,023	[6],[7]	233,155	[8]	219,595	[9]	217,635	[10]	$ 955,136	$ 880,408	$ 915,153
Gross profit	383,238	[1],[2]		345,038		323,918	[4]	287,635	[5]	309,535	[6],[7]	333,693	[8]	307,334	[9]	269,832	[10]	1,339,829	1,220,394	1,221,453
Selling and administrative	117,092	[1],[2]		109,166		108,811	[4]	102,013	[5]	100,552	[6],[7]	100,202	[8]	99,410	[9]	90,505	[10]	437,084	390,669	348,913
Engineering and development	86,794	[1],[2]		77,804		81,434	[4]	76,791	[5]	74,706	[6],[7]	77,049	[8]	75,342	[9]	74,408	[10]	322,824	301,505	307,305
Acquired intangible assets amortization	9,784	[1],[2]		9,647		10,083	[4]	10,634	[5]	10,558	[6],[7]	11,142	[8]	9,793	[9]	7,698	[10]	40,147	39,191	30,530
Restructuring and other	(2,088)		$ (6,500)			(10,404)		5,112		11,446		1,710		2,389		(313)		(13,880)	15,232	9,362
Total operating expenses	211,582	[1],[2]		190,117		189,924	[4]	194,550	[5]	197,262	[6],[7]	190,103	[8]	186,934	[9]	172,298	[10]	786,175	746,597	696,110
Income from operations	171,656	[1],[2]		154,921		133,994	[4]	93,085	[5]	112,273	[6],[7]	143,590	[8]	120,400	[9]	97,534	[10]	553,654	473,797	525,343
Interest income	(6,145)	[1],[2]		(5,159)		(5,430)	[4]	(8,052)	[5]	(9,083)	[6],[7]	(6,213)	[8]	(5,427)	[9]	(5,981)	[10]	(24,785)	(26,704)	(17,805)
Interest expense	5,950	[1],[2]		5,682		5,800	[4]	5,713	[5]	13,182	[6],[7]	5,557	[8]	5,639	[9]	6,890	[10]	23,145	31,269	21,663
Other (income) expense, net	22,965	[1],[2]		2,665		2,447	[4]	1,445	[5]	(2,954)	[6],[7]	3,405	[8]	176	[9]	805	[10]	29,522	1,431	(2,927)
Income before income taxes	148,886	[1],[2]		151,733		131,177	[4]	93,979	[5]	111,128	[6],[7]	140,841	[8]	120,012	[9]	95,820	[10]	525,772	467,801	524,412
Income tax (benefit) provision	23,811	[1],[2]		15,873		33,780	[4]	(15,159)	[5]	(32,662)	[6],[7]	20,863	[8]	18,975	[9]	8,846	[10]	58,304	16,022	266,720
Net income	$ 125,075	[1],[2]		$ 135,860		$ 97,397	[4]	$ 109,138	[5]	$ 143,790	[6],[7]	$ 119,978	[8]	$ 101,037	[9]	$ 86,974	[10]	$ 467,468	$ 451,779	$ 257,692
Net income per common share—basic	$ 0.75	[1],[2]		$ 0.80		$ 0.57	[4]	$ 0.63	[5]	$ 0.80	[6],[7]	$ 0.65	[8]	$ 0.53	[9]	$ 0.45	[10]	$ 2.74	$ 2.41	$ 1.30
Net income per common share—diluted	0.69	[1],[2]		0.75		0.55	[4]	0.62	[5]	0.79	[6],[7]	0.63	[8]	0.52	[9]	0.43	[10]	2.60	2.35	1.28
Cash dividend declared per common share	$ 0.09	[1],[2]		$ 0.09		$ 0.09	[4]	$ 0.09	[5]	$ 0.09	[6],[7]	$ 0.09	[8]	$ 0.09	[9]	$ 0.09	[10]	$ 0.36	$ 0.36	$ 0.28
Product [Member]
Quarterly Financial Information [Line Items]
Total revenues	$ 548,552	[1],[2]		$ 488,170		$ 457,511	[4]	$ 393,442	[5]	$ 420,652	[6],[7]	$ 470,994	[8]	$ 434,051	[9]	$ 403,925	[10]
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	226,184	[1],[2]		197,196		193,299	[4]	165,368	[5]	170,064	[6],[7]	195,339	[8]	180,777	[9]	180,958	[10]	$ 782,047	$ 727,138	$ 760,967
Service [Member]
Quarterly Financial Information [Line Items]
Total revenues	106,098	[1],[2]		93,868		106,667	[4]	100,657	[5]	98,906	[6],[7]	95,854	[8]	92,878	[9]	83,542	[10]
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 45,228	[1],[2]		$ 39,804		$ 46,961	[4]	$ 41,096	[5]	$ 39,959	[6],[7]	$ 37,816	[8]	$ 38,818	[9]	$ 36,677	[10]	$ 173,089	$ 153,270	$ 154,186

[1] Restructuring and other includes a $5.8 million gain for the decrease in the fair value adjustment to the MiR acquisition contingent consideration, partially offset by a $3.0 million fair value adjustment to increase the AutoGuide acquisition contingent consideration, $0.5 million of employee severance charges and $0.2 million of acquisition related expenses and compensation.

[2] Teradyne recorded pension and post retirement net actuarial losses of $7.7 million for the fourth quarter in 2019. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[3] Restructuring and other includes a $7.8 million gain for the decrease in the fair value of MiR contingent consideration liability, partially offset by $0.8 million of employee severance charges and $0.5 million of acquisition related expenses and compensation.

[4] Restructuring and other includes a $11.7 million gain for the decrease in the fair value of the MiR contingent consideration liability, partially offset by $0.8 million of employee severance charges and $0.5 million of acquisition related expenses and compensation.

[5] Restructuring and other includes a $3.0 million fair value adjustment to increase the MiR acquisition contingent consideration, $1.3 million of acquisition related expenses and compensation and $0.8 million of employee severance charges.

[6] Restructuring and other includes a $17.7 million fair value adjustment to increase the MiR acquisition contingent consideration, $0.8 million of employee severance charges, and $0.5 million acquisition related expenses and compensation, partially offset by a $7.4 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability.

[7] Teradyne recorded pension and post retirement net actuarial gains of $3.5 million for the fourth quarter in 2018. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[8] Restructuring and other includes $1.7 million of employee severance charges, $0.8 million of acquisition related expenses and compensation, partially offset by a $0.8 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability.

[9] Restructuring and other includes a $5.0 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $3.9 million of employee severance charges and $0.8 million of acquisition related expenses and compensation.

[10] Restructuring and other includes a $3.5 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $2.5 million of acquisition related expenses and compensation and $2.4 million of employee severance charges.