Teradyne (TER) 10-K 1 Mar 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Feb. 25, 2019	Jun. 29, 2018
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Entity Registrant Name	TERADYNE, INC
Entity Central Index Key	97,210
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 6.4
Trading Symbol	TER
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		173,629,283

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents		$ 926,752	$ 429,843
Marketable securities		190,096	1,347,979
Accounts receivable, less allowance for doubtful accounts of $1,673 and $2,219 in 2018 and 2017, respectively		291,267	272,783
Inventories, net		153,541	107,525
Prepayments and other current assets		170,826	112,151
Total current assets		1,732,482	2,270,281
Property, plant and equipment, net		279,821	268,447
Marketable securities		87,731	125,926
Deferred tax assets		70,848	84,026
Retirement plans assets		16,883	17,491
Other assets		11,509	12,275
Acquired intangible assets, net		125,482	79,088
Goodwill		381,850	252,011
Total assets	[1]	2,706,606	3,109,545
Current liabilities:
Accounts payable		100,688	86,393
Accrued employees' compensation and withholdings		148,566	141,694
Deferred revenue and customer advances		77,711	83,614
Other accrued liabilities		78,272	59,083
Contingent consideration		34,865	24,497
Income taxes payable		36,185	59,055
Total current liabilities		476,287	454,336
Retirement plans liabilities		117,456	119,776
Long-term deferred revenue and customer advances		32,750	30,127
Long-term contingent consideration		35,678	20,605
Deferred tax liabilities		20,662	6,720
Long-term other accrued liabilities		37,547	10,273
Long-term income taxes payable		83,891	148,075
Long-term debt		379,981	365,987
Total liabilities		1,184,252	1,155,899
Commitments and contingencies (Note K)
Shareholders' equity
Common stock, $0.125 par value, 1,000,000 shares authorized, 175,522 and 195,548 shares issued and outstanding at December 31, 2018 and 2017, respectively		21,940	24,444
Additional paid-in capital		1,671,645	1,638,413
Accumulated other comprehensive (loss) income		(13,040)	18,776
(Accumulated deficit) Retained earnings		(158,191)	272,013
Total shareholders' equity		1,522,354	1,953,646
Total liabilities and shareholders' equity		$ 2,706,606	$ 3,109,545
[1]	Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, less allowance for doubtful accounts	$ 1,673	$ 2,219
Common stock, par value	$ 0.125	$ 0.125
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	175,522,000	195,548,000
Common stock, shares outstanding	175,522,000	195,548,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2018	[1],[2]	Sep. 30, 2018	[2],[3]	Jul. 01, 2018	[2],[4]	Apr. 01, 2018	[5]	Dec. 31, 2017	[6],[7]	Oct. 01, 2017	[7],[8]	Jul. 02, 2017	[7],[9]	Apr. 02, 2017	[10]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 519,558		$ 566,848		$ 526,929		$ 487,467		$ 479,415		$ 503,378		$ 696,901		$ 456,913		$ 2,100,802	$ 2,136,606	$ 1,753,250
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	210,023		233,155		219,595		217,635		208,485		208,509		306,263		191,897		880,408	915,153	794,642
Gross profit	309,535		333,693		307,334		269,832		270,930		294,869		390,638		265,016		1,220,394	1,221,453	958,608
Operating expenses:
Selling and administrative	100,552		100,202		99,410		90,505		87,880		86,130		90,111		84,792		390,669	348,913	316,544
Engineering and development	74,706		77,049		75,342		74,408		72,070		76,986		82,270		75,978		301,505	307,305	292,159
Acquired intangible assets amortization	10,558		11,142		9,793		7,698		7,384		7,028		8,166		7,952		39,191	30,530	52,648
Restructuring and other	11,446		1,710		2,389		(313)		8,970		(4,407)		2,288		2,511		15,232	9,362	21,942
Goodwill impairment																			254,946
Acquired intangible assets impairment																	8,800		83,339
Total operating expenses	197,262		190,103		186,934		172,298		176,304		165,737		182,835		171,233		746,597	696,110	1,021,578
Income (loss) from operations	112,273		143,590		120,400		97,534		94,626		129,132		207,803		93,783		473,797	525,343	(62,970)
Non-operating (income) expenses:
Interest income	(9,083)		(6,213)		(5,427)		(5,981)		(6,476)		(4,517)		(3,292)		(3,520)		(26,704)	(17,805)	(9,296)
Interest expense	13,182		5,557		5,639		6,890		5,380		5,372		5,509		5,402		31,269	21,663	3,637
Other (income) expense, net	(2,954)		3,405		176		805		(2,362)		840		(1,291)		(115)		1,431	(2,927)	(2,251)
Income (loss) before income taxes	111,128		140,841		120,012		95,820		98,084		127,437		206,877		92,016		467,801	524,412	(55,060)
Income tax provision (benefit)	(32,662)		20,863		18,975		8,846		204,007		24,017		31,901		6,795		16,022	266,720	(11,639)
Net income (loss)	$ 143,790		$ 119,978		$ 101,037		$ 86,974		$ (105,923)		$ 103,420		$ 174,976		$ 85,221		$ 451,779	$ 257,692	$ (43,421)
Net income (loss) per common share:
Basic	$ 0.80		$ 0.65		$ 0.53		$ 0.45		$ (0.54)		$ 0.52		$ 0.88		$ 0.43		$ 2.41	$ 1.30	$ (0.21)
Diluted	0.79		0.63		0.52		0.43		(0.54)		0.52		0.87		0.42		$ 2.35	$ 1.28	$ (0.21)
Weighted average common shares-basic																	187,672	198,069	202,578
Weighted average common shares-diluted																	192,605	201,641	202,578
Cash dividend declared per common share	$ 0.09		$ 0.09		$ 0.09		$ 0.09		$ 0.07		$ 0.07		$ 0.07		$ 0.07		$ 0.36	$ 0.28	$ 0.24
Product [Member]
Revenues:
Total revenues	$ 420,652		$ 470,994		$ 434,051		$ 403,925		$ 388,282		$ 412,854		$ 610,356		$ 373,204		$ 1,729,621	$ 1,784,695	$ 1,453,248
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	170,064		195,339		180,777		180,958		168,672		169,661		267,752		154,883		727,138	760,967	660,056
Service [Member]
Revenues:
Total revenues	98,906		95,854		92,878		83,542		91,133		90,524		86,545		83,709		371,181	351,911	300,002
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 39,959		$ 37,816		$ 38,818		$ 36,677		$ 39,813		$ 38,848		$ 38,511		$ 37,014		$ 153,270	$ 154,186	$ 134,586
[1]	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.
[2]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[3]	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.
[4]	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.
[5]	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.
[6]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[7]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[8]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[9]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[10]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income (loss)	$ 451,779	$ 257,692	$ (43,421)
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustment, net of tax of $0, $0, $0	(28,442)	37,840	(13,162)
Available-for-sale marketable securities:
Unrealized (losses) gains on marketable securities arising during period, net of tax of $(722), $1,903, $923, respectively	(2,110)	1,863	2,037
Less: Reclassification adjustment for losses (gains) included in net income, net of tax of $(255), $(297), $(21) respectively	1,337	(441)	(683)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Total	(773)	1,422	1,354
Defined benefit pension and post-retirement plans:
Amortization of prior service benefit included in net periodic pension and post-retirement benefit, net of tax $(71), $(154), $(190), respectively	(245)	(272)	(321)
Prior service benefit arising during period, net of tax of $0, $0, $34, respectively			59
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(245)	(272)	(262)
Other comprehensive (loss) income	(29,460)	38,990	(12,070)
Comprehensive income (loss)	$ 422,319	$ 296,682	$ (55,491)

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Foreign currency translation adjustments, tax	$ 0	$ 0	$ 0
Unrealized (losses) gains on marketable securities arising during period, tax	(722)	1,903	923
Reclassification adjustment for losses (gains) included in net income, tax	(21)	(297)	(255)
Amortization of net prior service (credit) cost included in net periodic pension and post-retirement expense/income, tax	(71)	(154)	(190)
Prior service credit, tax	$ 0	$ 0	$ 34

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at Dec. 31, 2015		$ 1,965,786	$ 25,455	$ 1,480,647	$ (8,144)	$ 467,828
Balance, Shares at Dec. 31, 2015			203,641
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax (in shares)			2,377
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax		10,665	$ 297	10,368
Equity component of convertible debt		100,836		100,836
Equity component of convertible notes issuance cost		(2,017)		(2,017)
Purchase of convertible notes hedges		(100,834)		(100,834)
Proceeds from issuance of warrants		67,852		67,852
Stock-based compensation expense		30,745		30,745
Repurchase of common stock		$ (146,331)	$ (855)			(145,476)
Repurchase of common stock (in shares)		6,800	(6,841)
Tax benefit related to stock options and restricted stock units		$ 6,087		6,087
Cash dividends		(48,639)				(48,639)
Net income (loss)		(43,421)				(43,421)
Foreign currency translation adjustment		(13,162)			(13,162)
Unrealized gains (losses) on marketable securities:
Unrealized (losses) gains on marketable securities arising during period, net of tax of $923, 1903, (722) respectively		2,037			2,037
Less: Reclassification adjustment for losses (gains) included in net income, net of tax of $(255), $(297), $(21) respectively		(683)			(683)
Amortization of prior service benefit, net of tax of $(190), $(154), $(71) respectively		(321)			(321)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax of $769					1,004
Prior service income arising during period, net of tax of $34		59			59
Balance at Dec. 31, 2016		1,828,659	$ 24,897	1,593,684	(20,214)	230,292
Balance, Shares at Dec. 31, 2016			199,177
Net income (loss)	[1]	85,221
Balance at Dec. 31, 2016		1,828,659	$ 24,897	1,593,684	(20,214)	230,292
Balance, Shares at Dec. 31, 2016			199,177
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax (in shares)			2,211
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax		11,024	$ 277	10,747
Stock-based compensation expense		33,982		33,982
Repurchase of common stock		(200,304)	$ (730)			(199,574)
Repurchase of common stock (in shares)			(5,840)
Cumulative effect adjustment for prior year tax benefits related to stock options and restricted stock units		39,081				39,081
Cash dividends		(55,478)				(55,478)
Net income (loss)		257,692				257,692
Foreign currency translation adjustment		37,840			37,840
Unrealized gains (losses) on marketable securities:
Unrealized (losses) gains on marketable securities arising during period, net of tax of $923, 1903, (722) respectively		1,863			1,863
Less: Reclassification adjustment for losses (gains) included in net income, net of tax of $(255), $(297), $(21) respectively		(441)			(441)
Amortization of prior service benefit, net of tax of $(190), $(154), $(71) respectively		(272)			(272)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax of $769		713			713
Balance at Dec. 31, 2017		1,953,646	$ 24,444	1,638,413	18,776	272,013
Balance, Shares at Dec. 31, 2017			195,548
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax (in shares)			1,613
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax		129	$ 201	(72)
Stock-based compensation expense		33,304		33,304
Repurchase of common stock		(832,356)	$ (2,705)			(829,651)
Repurchase of common stock (in shares)			(21,639)
Cash dividends		(67,367)				(67,367)
Net income (loss)		451,779				451,779
Foreign currency translation adjustment		(28,442)			(28,442)
Unrealized gains (losses) on marketable securities:
Unrealized (losses) gains on marketable securities arising during period, net of tax of $923, 1903, (722) respectively		(2,110)			(2,110)
Less: Reclassification adjustment for losses (gains) included in net income, net of tax of $(255), $(297), $(21) respectively		1,337			1,337
Reclassification of unrealized gains on equity securities, net of tax of $(902)		0			(3,125)	3,125
Amortization of prior service benefit, net of tax of $(190), $(154), $(71) respectively		(245)			(245)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax of $769		0			769	(769)
Balance at Dec. 31, 2018		1,522,354	$ 21,940	$ 1,671,645	$ (13,040)	(158,191)
Balance, Shares at Dec. 31, 2018			175,522
Unrealized gains (losses) on marketable securities:
Cumulative effect of changes in accounting principle related to revenue recognition		$ 12,679				$ 12,679
[1]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

CONSOLIDATED STATEMENTS OF SH_2

CONSOLIDATED STATEMENTS OF SHAREHOLDERS EQUITY (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Issuance of stock to employees under benefit plans, shares withheld for payroll tax	$ 20,025
Cumulative effect of changes in accounting principle, net of tax	(1,670)
Unrealized (losses) gains on marketable securities arising during period, tax	(722)
Reclassification adjustment for gains included in net income, tax	(21)
Amortization of prior service (credit) cost included in net periodic pension and post-retirement expense/income, tax	(71)
Prior service income arising during period, tax	0
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings Tax Effect	769
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Reclassification adjustment for gains included in net income, tax	(902)
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings Tax Effect	$ (691)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ 451,779	$ 257,692	$ (43,421)
Adjustments to reconcile net income (loss) from operations to net cash provided by operating activities:
Depreciation	67,415	66,122	64,782
Amortization	45,809	41,953	55,227
Stock-based compensation	33,577	34,097	30,750
Deferred taxes	28,340	37,105	(62,936)
Provision for excess and obsolete inventory	11,242	8,844	17,493
Contingent consideration fair value adjustment	987	7,820	15,896
Losses (gains) on investments	3,494	(878)	(1,050)
Retirement plans actuarial gains	(3,316)	(6,624)	(3,203)
Property insurance recovery, net		(4,309)
Goodwill impairment			254,946
Acquired intangible assets impairment	8,800		83,339
Tax benefit related to employee stock compensation awards			(6,198)
Other	1,083	1,585	602
Changes in operating assets and liabilities, net of businesses acquired:
Accounts receivable	(17,938)	(80,584)	18,325
Inventories	(29,498)	44,960	34,263
Prepayments and other assets	(58,402)	2,254	(19,194)
Accounts payable and other accrued expenses	13,693	43,574	6,820
Deferred revenue and customer advances	13,379	4,984	(3,634)
Retirement plan contributions	(4,334)	(5,902)	(6,044)
Income taxes	(80,429)	173,802	18,434
Net cash provided by operating activities	476,881	626,495	455,197
Cash flows from investing activities:
Purchases of property, plant and equipment	(114,379)	(105,375)	(85,272)
Proceeds from government subsidy for property, plant and equipment	7,920
Purchases of marketable securities	(918,744)	(1,391,917)	(1,656,267)
Proceeds from maturities of marketable securities	1,270,439	701,681	243,232
Proceeds from sales of marketable securities	846,122	527,746	852,794
Proceeds from insurance	1,126	5,064	5,051
Acquisition of businesses, net of cash acquired	(169,474)
Net cash provided by (used for) investing activities	923,010	(262,801)	(640,462)
Cash flows from financing activities:
Issuance of common stock under stock purchase and stock option plans	20,973	24,493	20,473
Repurchase of common stock	(823,478)	(200,304)	(146,331)
Dividend payments	(67,322)	(55,447)	(48,619)
Payments related to net settlement of employee stock compensation awards	(20,023)	(12,881)	(9,398)
Payments of contingent consideration	(13,571)	(1,050)	(11,697)
Proceeds from issuance of convertible notes, net of issuance costs			450,800
Purchase of convertible note hedges			(100,834)
Proceeds from issuance of warrants			67,852
Tax benefit related to employee stock compensation awards			6,198
Net cash (used for) provided by financing activities	(903,421)	(245,189)	228,444
Effects of exchange rate changes on cash and cash equivalents	439	3,454
Increase in cash and cash equivalents	496,909	121,959	43,179
Cash and cash equivalents at beginning of year	429,843	307,884	264,705
Cash and cash equivalents at end of year	926,752	429,843	307,884
Cash paid for:
Interest	6,205	6,446	446
Income taxes	$ 72,811	$ 53,775	$ 40,424

The Company

The Company	12 Months Ended
	Dec. 31, 2018
The Company	A. THE COMPANY Teradyne, Inc. (“Teradyne”) is a leading global supplier of automation equipment for test and industrial applications. Teradyne designs, develops, manufactures and sells automatic test systems used to test semiconductors, wireless products, data storage and complex electronics systems in the consumer electronics, wireless, automotive, industrial, computing, communications, and aerospace and defense industries. Teradyne’s industrial automation products include collaborative robotic arms, autonomous mobile robots and advanced robotic control software used by global manufacturing and light industrial customers to improve quality, increase manufacturing and material handling efficiency and decrease manufacturing costs. Teradyne’s automatic test equipment and industrial automation products and services include: • semiconductor test (“Semiconductor Test”) systems; • defense/aerospace (“Defense/Aerospace”) test instrumentation and systems, storage test (“Storage Test”) systems, and circuit-board test and inspection (“Production Board Test”) systems (collectively these products represent “System Test”); • industrial automation (“Industrial Automation”) products; and • wireless test (“Wireless Test”) systems. On June 11, 2015, Teradyne acquired Universal Robots A/S (“Universal Robots”) for approximately $284 million of cash plus up to an additional $65 million of cash if certain performance targets are met extending through 2018. Universal Robots is the leading supplier of collaborative robots which are low-cost, easy-to-deploy and simple-to-program robots that work side by side with production workers. Universal Robots is a separate operating and reportable segment, Industrial Automation. On February 26, 2018, Teradyne acquired Energid Technologies Corporation (“Energid”) for a total purchase price of approximately $28 On April 25, 2018, Teradyne acquired Mobile Industrial Robots ApS (“MiR”), a Danish limited liability company, for a total purchase price of approximately $198 $145 million of cash paid and $53 $115 Universal Robots, MiR and Energid are included in Teradyne’s Industrial Automation segment.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies	B. ACCOUNTING POLICIES The consolidated financial statements include the accounts of Teradyne and its wholly-owned subsidiaries. All significant intercompany balances and transactions are eliminated. Certain prior years’ amounts were reclassified to conform to the current year presentation. Preparation of Financial Statements and Use of Estimates The preparation of consolidated financial statements requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent liabilities. On an on-going Revenue Recognition Revenue from Contracts with Customers Teradyne adopted Accounting Standards Codification (“ASC”) 606, “ Revenue from Contracts with Customers” “Revenue Recognition,” In accordance with ASC 606, Teradyne recognizes revenues, when or as control is transferred to a customer. Teradyne’s determination of revenue is dependent upon a five step process outlined below. Step 1: Identify the contract with the customer Teradyne accounts for a contract with a customer when there is written approval, the contract is committed, the rights of the parties, including payment terms, are identified, the contract has commercial substance and consideration is probable of collection. Step 2: Identify the performance obligations in the contract Teradyne periodically enters into contracts with customers in which a customer may purchase a combination of goods and services, such as products with extended warranty obligations. Teradyne determines performance obligations by assessing whether the products or services are distinct from the other elements of the contract. In order to be distinct, the product or service must perform either on its own or with readily available resources and must be separate within the context of the contract. Step 3: Determine the transaction price Teradyne considers the amount stated on the face of the purchase order to be the transaction price. Teradyne does not have material variable consideration which could impact the stated purchase price agreed to by Teradyne and the customer. Step 4: Allocate the transaction price to the performance obligations in the contract Transaction price is allocated to each individual performance obligation based on the standalone selling price of that performance obligation. Teradyne uses standalone transactions when available to value each performance obligation. If standalone transactions are not available, Teradyne will estimate the standalone selling price through market assessments or cost plus a reasonable margin analysis. Any discounts from standalone selling price are spread proportionally to each performance obligation. Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation In order to determine the appropriate timing for revenue recognition, Teradyne first determines if the transaction meets any of three criteria for over time recognition. If the transaction meets the criteria for over time recognition, Teradyne recognizes revenue as the good or service is delivered. Teradyne uses input variables such as hours or months utilized or costs incurred to determine the amount of revenue to recognize in a given period. Input variables are used as they best align consumption with benefit to the customer. For transactions that do not meet the criteria for over time recognition, Teradyne will recognize revenue at a point in time based on an assessment of the five criteria for transfer of control. Teradyne has concluded that revenue should be recognized when shipped or delivered based on contractual terms. Typically, acceptance of Teradyne’s products and services is a formality as Teradyne delivers similar systems, instruments and robots to standard specifications. In cases where acceptance is not deemed a formality, Teradyne will defer revenue recognition until customer acceptance. Revenue recognized in accordance with ASC 606 was $2,088.8 million for the twelve months ended December 31, 2018. For the twelve months ended December 31, 2018, Teradyne also recognized $12.0 million in revenue on leases of Teradyne systems, which are accounted for outside of ASC 606. Disaggregation of Revenue The following table provides information about disaggregated revenue by primary geographical market, major product line and timing of revenue recognition. For the Year Ended December 31, 2018 Semiconductor Test System Test Industrial Automation Wireless Test Corporate and Other Consolidated System on a Chip Memory Defense/ Aerospace Storage Test Production Board Test Universal Robots Mobile Industrial Robots Energid (in thousands) Americas Point in time $ 43,398 $ 14,579 $ 59,246 $ 767 $ 9,082 $ 68,289 $ 7,326 $ 543 $ 17,730 $ (1,205 ) $ 219,755 Over time 35,100 2,774 24,577 — 3,091 649 — 997 1,436 — 68,624 Europe, Middle East and Africa Point in time 50,988 9,726 3,056 — 16,733 105,776 10,839 — 3,821 — 200,939 Over time 21,584 1,125 2,124 — 6,467 1,000 — 1,591 1,147 — 35,038 Asia Pacific Point in time 916,107 235,061 2,769 58,004 17,761 57,830 5,950 10 100,985 — 1,394,477 Over time 140,887 10,203 965 7,877 3,221 551 — 101 6,127 — 169,932 Lease revenue 10,885 — — — 392 — — — 760 — 12,037 Total $ 1,218,949 $ 273,468 $ 92,737 $ 66,648 $ 56,747 $ 234,095 $ 24,115 $ 3,242 $ 132,006 $ (1,205 ) $ 2,100,802 Performance Obligations Hardware Teradyne hardware consists primarily of semiconductor test systems and instruments, defense/aerospace test instrumentation and systems, storage test systems and instruments, circuit-board test and inspection systems and instruments, collaborative robots, autonomous mobile robots and wireless test systems. The hardware includes a standard 12-month warranty. This warranty is not considered a distinct performance obligation because it does not obligate Teradyne to provide a separate service to the customer and it cannot be purchased separately. Teradyne’s hardware is recognized at a point in time upon transfer of control to the customer. Extended Warranty Customers have the option to purchase an extended warranty, which extends the warranty period for systems and robots beyond the one-year Training and Applications Support Teradyne sells training and applications support to customers either in standalone transactions or included with system purchases. The training and support allow the customer to use Teradyne’s systems efficiently and effectively. Training and applications support included in system orders are valued based on their standalone selling price and all training and applications support is recognized over time as the customer receives and consumes the benefit associated with each. Both are recognized using an input method of hours consumed as this best depicts the transfer of services to the customer. Service Agreements Service agreements are recognized ratably over the period of agreement based on months completed. Post-Contract Customer Support (“PCS”) Teradyne provides support services for certain systems and robots outside of warranty. These services include telephone support, bug fixes, and when-and-if Teradyne does not allow customer returns or provide refunds to customers for any products or services. Contract Balances The following table provides information about contract liabilities. Teradyne does not have material contract assets on the balance sheet. December 31, 2018 January 1, 2018 (as adjusted) Increase (in thousands) Deferred revenue and customer advances $ 77,711 $ 76,638 $ 1,073 Long-term deferred revenue and customer advances 32,750 20,848 11,902 The amount of revenue recognized during the twelve months ended December 31 , 2018 that was previously included within the deferred revenue and customer advances balance was Practical Expedients Teradyne has adopted the practical expedients available within ASC 340 “Other Assets and Deferred Costs” Teradyne has adopted the practical expedient, which states an entity need not adjust the promised amount of consideration for the effects of a significant financing component if the entity expects, at contract inception, that the period between when the entity transfers a promised good or service to the customer and when the customer pays for that good or service will be one year or less. Teradyne does not have material payments associated with performance obligations outside this one-year Impacts The following tables summarize the impact of ASC 606 to Teradyne’s consolidated financial statements. Differences are the result of timing differences between the recognition of revenue under ASC 606 and ASC 605 primarily with respect to software transactions deferred due to lack of vendor specific objective evidence of price under ASC 605 and Teradyne’s assessment of acceptance under ASC 606. Under Legacy GAAP, Teradyne did not recognize revenue prior to acceptance if payment, title, or risk of loss was tied to acceptance. Under ASC 606, Teradyne recognizes revenue prior to receipt of acceptance if acceptance is deemed a formality. Condensed Consolidated Balance Sheet: December 31, 2018 As Reported Adjustments to Recognize under Legacy GAAP Legacy GAAP (in thousands, except per share amount) Assets Accounts receivable, less allowance for doubtful accounts $ 291,267 $ (37,348 ) $ 253,919 Inventories, net 153,541 10,759 164,300 Deferred tax assets 70,848 (3,874 ) 66,974 Liabilities Deferred revenue and customer advances $ 77,711 $ (4,118 ) $ 73,593 Income taxes payable 36,185 (4,495 ) 31,690 Long-term deferred revenue and customer advances 32,750 (10,303 ) 22,447 Shareholders’ equity Accumulated deficit $ (158,191 ) $ (11,547 ) $ (169,738 ) Condensed Consolidated Stateme nt of Operation: For the Year Ended December 31, 2018 As Reported Adjustments to Recognize under Legacy GAAP Legacy GAAP (in thousands, except per share amount) Total revenues $ 2,100,802 $ (39,184 ) $ 2,061,618 Total cost of revenues 880,408 (10,760 ) 869,648 Income tax provision 16,022 (4,197 ) 11,825 Net income 451,779 (24,227 ) 427,552 Net income per common share: Basic $ 2.41 $ (0.13 ) $ 2.28 Diluted $ 2.35 $ (0.13 ) $ 2.22 As of December 31, 2018 and 2017, deferred revenue and customer advances consisted of the following and are included in the short and long-term deferred revenue and customer advances: 2018 2017 (in thousands) Maintenance and training $ 58,362 $ 57,256 Extended warranty 27,422 24,438 Customer advances, undelivered elements and other 24,677 32,047 Total deferred revenue and customer advances $ 110,461 $ 113,741 Product Warranty When Teradyne receives revenue for extended warranties, beyond one year, it is deferred and recognized on a straight-line basis over the contract period. Related costs are expensed as incurred. The balance below is included in short and long-term deferred revenue and customer advances: Amount (in thousands) Balance at December 31, 2015 $ 30,024 Deferral of new extended warranty revenue 19,909 Recognition of extended warranty deferred revenue (21,733 ) Balance at December 31, 2016 28,200 Deferral of new extended warranty revenue 20,513 Recognition of extended warranty deferred revenue (24,275 ) Balance at December 31, 2017 24,438 Deferral of new extended warranty revenue 23,753 Recognition of extended warranty deferred revenue (20,769 ) Balance at December 31, 2018 $ 27,422 Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable are recorded at the invoiced amount and do not bear interest. The volatility of the industries that Teradyne serves can cause certain of its customers to experience shortages of cash flows, which can impact their ability to make required payments. Teradyne maintains allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. Estimated allowances for doubtful accounts are reviewed periodically taking into account the customer’s recent payment history, the customer’s current financial statements and other information regarding the customer’s credit worthiness. Account balances are written off against the allowance when it is determined the receivable will not be recovered. Teradyne sells certain trade accounts receivables on a non-recourse basis to third-party financial institutions pursuant to factoring agreements. Teradyne accounts for these transactions as sales of receivables and presents cash proceeds as a cash provided by operating activities in the consolidated statements of cash flows. Total trade accounts receivable sold under the factoring agreements were $52.2 million and $5.4 million during 2018 and 2017, respectively. Factoring fees for the sales of receivables were recorded in interest expense and were not material. Inventories Inventories are stated at the lower of cost (first-in, first-out Investments Teradyne accounts for its investments in debt and equity securities in accordance with the provisions of ASC 320-10, Investments—Debt and Equity Securities 320-10 available-for-sale held-to-maturity • The length of time and the extent to which the market value has been less than cost; • The financial condition and near-term prospects of the issuer; and • The intent and ability to retain the investment in the issuer for a period of time sufficient to allow for any anticipated recovery in market value. Teradyne uses the market and income approach techniques to value its financial instruments and there were no changes in valuation techniques during the twelve months ended December 31, 2018 and 2017. As defined in ASC 820-10, “ Fair Value Measurements and Disclosures, Level 1: Quoted prices in active markets for identical assets as of the reporting date; Level 2: Inputs other than Level 1, that are observable either directly or indirectly as of the reporting date. For example, a common approach for valuing fixed income securities is the use of matrix pricing. Matrix pricing is a mathematical technique used to value securities by relying on the securities’ relationship to other benchmark quoted prices, and is considered a Level 2 input; or Level 3: Unobservable inputs that are not supported by market data. Unobservable inputs are developed based on the best information available, which might include ’s own data. In accordance with ASC 820-10, Teradyne measures its debt and equity investments at fair value. Teradyne’s debt investments are classified as Level 2, and equity investments are classified as Level 1. Acquisition-related contingent consideration is classified as Level 3. Teradyne determines the fair value of acquisition-related contingent consideration using a Monte Carlo simulation model. Assumptions utilized in the model include forecasted revenues, revenue volatility, earnings before interest and taxes, and discount rate. Financial Assets and Financial Liabilities In January 2016 , the Financial Accounting Standards Board (“FASB”) issued ASU 2016 - 01 , “Financial Instruments—Overall (Subtopic 825 - 10) : Recognition and Measurement of Financial Assets and Financial Liabilities.” Teradyne adopted the new accounting guidance in the first quarter of 2018 using the modified retrospective approach. This guidance requires that changes in fair value of equity securities be accounted for directly in earnings. Previously, the changes in fair value were recorded in accumulated other comprehensive income on the balance sheet. Teradyne continues to record realized gains in interest income and realized losses in interest expense. The adoption of this new accounting guidance increased the January 1 , 2018 retained earnings balance by $3.1 Prepayments Prepayments consist of the following and are included in prepayments and other current assets on the balance sheet: 2018 2017 (in thousands) Contract manufacturer and supplier prepayments $ 131,642 $ 82,503 Prepaid taxes 9,646 5,039 Prepaid maintenance and other services 8,487 8,189 Other prepayments 12,744 12,386 Total prepayments $ 162,519 $ 108,117 Retirement and Postretirement Plans Teradyne recogn izes net ac tuarial gains and losses and the change in the fair value of the plan assets in its operating results in the year in which they occur or upon any interim remeasurement of the plans. Teradyne calculates the expected return on plan assets using the fair value of the plan assets. Actuarial gains and losses are generally measured annually as of December 31 and, accordingly, recorded during the fourth quarter of each year or upon any interim remeasurement of the plans. Retirement Benefits In March 2017 , the FA SB issu ed ASU 2017 - 07 , “ Compensation—Retirement Benefits (Topic 715) : Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost 2018 . This guidance requires the service cost component of net benefit costs to be reported in the same line item in the consolidated statement of operations as other employee compensation costs. The non-service components of net benefit costs such as interest cost, expected return on assets, amortization of prior service cost, and actuarial gains or losses, are required to be reported separately outside of income or loss from operations. Following the adoption of this guidance, Teradyne continues to record the service cost component in the same line item as other employee compensation costs and the non-service components of net benefit costs such as interest cost, expected return on assets, amortization of prior service cost, and actuarial gains or losses are reported within other (income) expense, net. In the twelve months ended December 31 , 2017 and 2016 , the retrospective adoption of this standard decreased income from operations by $ 5.0 million and $ 3.0 million, respectively, due to the removal of net actuarial pension gains and increased non-operating (income) expense by the same amount with no impact to net income. Goodwill, Intangible and Long-Lived Assets Teradyne accounts for go odwill an d intangible assets in accordance with ASC 350 - 10 , Intangibles-Goodwill and Other. 31 , on a reporting unit basis, or more frequently when events and circumstances occur indicating that the recorded goodwill may be impaired. In accordance with ASC 350 - 10 , more likely than not two-step more likely than not two-step In accordance with ASC 360 - 10 , Impairmen t or Disposal of Long-Lived Assets, Property, Plant and Equipment Property, plant and equipment are stated at cos t and depreciated over the estimated useful lives of the assets. Leasehold improvements and major renewals are capitalized and included in property, plant and equipment accounts while expenditures for maintenance and repairs and minor renewals are charged to expense. When assets are retired, the assets and related accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in the consolidated statements of operations. Teradyne provides for depreciation of its assets principally on the straight-line method with the cost of the assets being charged to expense over their useful lives as follows: Buildings 40 years Building improvements 5 to 10 years Leasehold improvements Lesser of lease term or 10 years Furniture and fixtures 10 years Test systems manufactured internally 6 years Machinery and equipment 3 to 5 years Software 3 to 5 years Test systems manufactured internally are used by Te radyne for customer evaluations and manufacturing and support of its customers. Teradyne depreciates the test systems manufactured internally over a six-year 31 , 2018 , 2017 , and 2016 was $3.8 million, $3.6 million, and $11.4 million, respectively. Engineering and Development Costs Teradyne’s products are highly technical in nature and require a larg e and continuing engineering and development effort. Software development costs incurred prior to the establishment of technological feasibility are charged to expense. Software development costs incurred subsequent to the establishment of technological feasibility are capitalized until the product is available for release to customers. To date, the period between achieving technological feasibility and general availability of the product has been short and software development costs eligible for capitalization have not been material. Engineering and development costs are expensed as incurred and consist primarily of salaries, contractor fees including non-recurring Stock Compensation Plans and Employee Stock Purchase Plan Stock-based compensation expense is based on the grant-date fair val ue e 718 - 10 , Compensation-Stock Compensation In March 2016 , the FASB issued ASU 2016 - 09 , “Compensation-Stoc k C 718) : Improvements to Employee Share-Based Payment Accounting.” 2017 . This ASU changes how Teradyne accounts for certain aspects of share-based payment awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statements of cash flows. Adoption of this ASU required recognition of a cumulative effect adjustment to reta million was recorded in the first quarter of 2017 as an increase to retained earnings and deferred tax assets. This ASU also required a change in how Teradyne recognizes the excess tax benefits or tax defic 2016 - 09 , paid-in 2016 - 09 , 2017 , these excess tax benefits or tax deficiencies are recognized as a discrete tax benefit or discrete tax expense to the current income tax provision in Teradyne’s consolidated statements of operations. ASU 2016 - 09 requires companies to adopt the amendment related to accounting for excess tax ben efit 2017 , Teradyne recognized a discrete tax benefit of $ 6.3 million related to net excess tax benefit. In addition, under ASU 2016 - 09 , as Upon adoption of ASU 2016 - 09 , or Under its stock compensation plans, Teradyne has granted stock options, restricted stock units and p erf Teradyne’s common stock through its Employee Stock Purchase Plan (“ESPP”). Income Taxes Deferred tax assets and liabilities are determined based on differences between financial re porti 740 , “Accounting for Income Taxes.” Advertising Costs Teradyne expenses all advertising costs as incurred. Adve million, $9.1 million, and $6.4 million in 2018 , 2017 , and 2016 , respectively. Translation of Non-U.S. The functional currency for all subsidiaries is the U.S. dollar, except for the Uni ver Net foreign exchange gains and losses resulting from remeasurement are included in other (incom e) e 31 , 2018 , 2017 , and 2016 , (gains) losses from the remeasurement of the monetary assets and liabilities denominated in foreign currencies were $(2.4) million, $2.9 million, and $(8.0) million, respectively. These amounts do not reflect the corresponding (gains) losses from foreign exchange con trac Net Income (Loss) per Common Share Basic net income (loss) per common share is calculated by dividing net income (loss) by the w With respect to its convertible debt issued in 2016 , Teradyne has determined that it has the abili ty a Teradyne is accounting for the conversion spread using the treasury stock method. Comprehensive Income (Loss) Comprehensive income (loss) includes net income, unrealized pension and postretirement prior service costs and benefits, unrealized gains and losses on investments in debt marketable securities and foreign currency translation adjustment. Prior to 2018, comprehensive income (loss) included unrealized gains and losses on investments in equity marketable securities.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	12 Months Ended
	Dec. 31, 2018
Recently Issued Accounting Pronouncements	C. RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS On January 26, 2017, the FASB issued ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment.” one-step In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842).” “Leases.”

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2018
Acquisitions	D. ACQUISITIONS Business Mobile Industrial Robots On April 25, 2018, Teradyne acquired all the issued and outstanding shares of MiR, a Danish limited liability company located in Odense, Denmark. MiR is the leading maker of collaborative autonomous mobile robots for industrial applications. MiR is part of Teradyne’s Industrial Automation segment. The total purchase price of $197.8 million included $145.2 million of cash paid and $52.6 million of contingent consideration measured at fair value. The contingent consideration is payable in Euros upon the achievement of certain thresholds and targets for revenue and earnings before interest and taxes for periods from January 1, 2018 to December 31, 2018; January 1, 2018 to December 31, 2019; and January 1, 2018 to December 31, 2020. At December 31, 2018, the maximum amount of contingent consideration that could be paid is $115 The valuation of the contingent consideration is dependent on the following assumptions: forecasted revenues, revenue volatility, earnings before interest and taxes, and discount rate. These assumptions were estimated based on a review of the historical and projected results. The MiR acquisition was accounted for as a business combination and, accordingly, the results have been included in Teradyne’s consolidated results of operations from the date of acquisition. MiR’s products will help expand the Industrial Automation segment, which is a key component of our growth strategy. The allocation of the total purchase price to MiR’s net tangible liabilities and identifiable intangible assets was based on their estimated fair values as of the acquisition date. The excess of the purchase price over the identifiable intangible assets and net tangible liabilities in the amount of $ 136.0 million was allocated to goodwill, which is not deductible for tax purposes. MiR’s results have been included in Teradyne’s Industrial Automation segment from the date of acquisition. The following table represents the final allocation of the purchase price: Purchase Price Allocation (in thousands) Goodwill $ 135,976 Intangible assets 80,670 Tangible assets acquired and liabilities assumed: Current assets 6,039 Non-current assets 1,336 Accounts payable and current liabilities (7,336 ) Long-term deferred tax liabilities (18,007 ) Other long-term liabilities (900 ) Total purchase price $ 197,778 Teradyne estimated the fair value of intangible assets using the income and cost approaches. Acquired intangible assets are amortized on a straight-line basis over their estimated useful lives. Components of these intangible assets and their estimated useful lives at the acquisition date are as follows: Fair Value Estimated Useful Life (in thousands) (in years) Developed technology $ 58,900 7.0 Trademarks and tradenames 13,240 11.0 Customer relationships 8,500 2.5 Backlog 30 0.2 Total intangible assets $ 80,670 7.2 For the period The following unaudited pro forma information gives effect to the acquisition of MiR as if the acquisition occurred on January 1, 2017. The unaudited pro forma results are not necessarily indicative of what actually would have occurred had the acquisition been in effect for the periods presented: For the Year Ended December 31, 2018 December 31, 2017 (in thousands, except per share amounts) Revenues $ 2,107,600 $ 2,148,320 Net income $ 450,559 $ 243,399 Net income per common share: Basic $ 2.40 $ 1.23 Diluted $ 2.34 $ 1.21 Pro forma results fo non-recurring Pro forma results for the year ende d non-recurring Energid Technologies Corporation On February 26, 2018, Teradyne acquired a ll of the issued and outstanding shares of Energid for a total purchase price of approximately $27.6 million. Energid’s technology enables and simplifies the programming of complex robotic motions used in a wide variety of end markets, ranging from heavy industry to healthcare, utilizing both traditional robots and collaborative robots. The Energid acquisition was accounted for as a business combination and, accordingly, Energid’s results have been included in Teradyne’s Industrial Automation segment from the date of acquisition. As of the acquisition date, Teradyne’s purchase price allocation was goodwill of $14.4 million which is deductible for tax purposes , acquired intangible assets of $12.3 million with an average estimated useful life of 7.7 years, and $1.0 million of net tangible assets. The acquisition was not material to Teradyne’s condensed consolidated financial statements.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2018
Inventories	E. INVENTORIES Inventories, net consisted of the following at December 31, 2018 and 2017: 2018 2017 (in thousands) Raw material $ 89,365 $ 62,668 Work-in-process 31,014 19,464 Finished goods 33,162 25,393 $ 153,541 $ 107,525 Inventory reserves for the years ended December 31, 2018 and 2017 were $100.8 million and $102.9 million, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment	F. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment, net consisted of the following at December 31, 2018 and 2017: 2018 2017 (in thousands) Land $ 16,561 $ 16,561 Buildings 105,935 98,369 Machinery and equipment 689,770 647,961 Furniture and fixtures, and software 90,384 88,539 Leasehold improvements 52,536 49,540 Construction in progress 6,276 13,522 961,462 914,492 Less: accumulated depreciation 681,641 646,045 $ 279,821 $ 268,447 Depreciation of property, plant and equipment for the years ended December 31, 2018, 2017, and 2016 was $67.4 million, $66.1 million, and $64.8 million, respectively. As of December 31, 2018 and 2017, the gross book value included in machinery and equipment for internally manufactured test systems being leased by customers was $5.5 million and $18.1 million, respectively. As of December 31, 2018 and 2017, the accumulated depreciation on these test systems was $5.2 million and $13.7 million, respectively.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2018
Financial Instruments	G. FINANCIAL INSTRUMENTS Cash Equivalents Teradyne considers all highly liquid investments with maturities of three months or less at the date of acquisition to be cash equivalents. Marketable Securities Effective January 1, 2018, Teradyne adopted ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Teradyne’s available-for-sale debt securities are classified as Level 2 and equity securities are classified as Level 1. Contingent consideration is classified as Level 3. The vast majority of Level 2 securities are fixed income securities priced by third party pricing vendors. These pricing vendors utilize the most recent observable market information in pricing these securities or, if specific prices are not available, use other observable inputs like market transactions involving identical or comparable securities. During the years ended December 31, 2018 and 2017, there were no transfers in or out of Level 1, Level 2, or Level 3 financial instruments. Realized gains recorded in 2018, 2017, and 2016 were $4.0 million, $1.1 million, and $1.6 million, respectively. Realized losses recorded in 2018, 2017, and 2016 were $1.6 million, $0.3 million, and $0.5 million, respectively. Realized gains are included in interest income and realized losses are included in interest expense. Unrealized gains and losses on available-for-sale Unrealized gains related to equity securities are included in interest income and unrealized losses are included in interest expense. Unrealized losses related to equity securities recognized in 2018 were $6.0 million. The cost of securities sold is based on the specific identification method. The following table sets forth by fair value hierarchy Teradyne’s financial assets and liabilities that were measured at fair value on a recurring basis as of December 31, 2018 and 2017: December 31, 2018 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 312,512 $ — $ — $ 312,512 Cash equivalents 253,525 360,715 — 614,240 Available for sale securities: U.S. Treasury securities — 109,721 — 109,721 Commercial paper — 86,117 — 86,117 Corporate debt securities — 40,020 — 40,020 U.S. government agency securities — 9,611 — 9,611 Certificates of deposit and time deposits — 7,604 — 7,604 Debt mutual funds 3,187 — — 3,187 Non-U.S. — 376 — 376 Equity securities: Mutual funds 21,191 — — 21,191 590,415 614,164 — 1,204,579 Derivative assets — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Contingent consideration $ — $ — $ 70,543 $ 70,543 Derivative liabilities — 514 — 514 Total $ — $ 514 $ 70,543 $ 71,057 Reported as follows: Level 1 Level 2 Level 3 Total (in thousands) Assets Cash and cash equivalents $ 566,037 $ 360,715 $ — $ 926,752 Marketable securities — 190,096 — 190,096 Long-term marketable securities 24,378 63,353 — 87,731 Prepayments — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Other current liabilities $ — $ 514 $ — $ 514 Contingent consideration — — 34,865 34,865 Long-term contingent consideration — — 35,678 35,678 Total $ — $ 514 $ 70,543 $ 71,057 December 31, 2017 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 197,955 $ — $ — $ 197,955 Cash equivalents 206,335 25,553 — 231,888 Available for sale securities: U.S. Treasury securities — 855,795 — 855,795 Commercial paper — 282,840 — 282,840 Certificates of deposit and time deposits — 167,342 — 167,342 Corporate debt securities — 133,186 — 133,186 Equity and debt mutual funds 23,430 — — 23,430 U.S. government agency securities — 10,726 — 10,726 Non-U.S. — 586 — 586 427,720 1,476,028 — 1,903,748 Derivative assets — 389 — 389 Total $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Contingent consideration $ — $ — $ 45,102 $ 45,102 Derivative liabilities — 446 — 446 Total $ — $ 446 $ 45,102 $ 45,548 Reported as follows: Level 1 Level 2 Level 3 Total (in thousands) Assets Cash and cash equivalents $ 404,290 $ 25,553 $ — $ 429,843 Marketable securities — 1,347,979 — 1,347,979 Long-term marketable securities 23,430 102,496 — 125,926 Prepayments — 389 — 389 $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Other current liabilities $ — $ 446 $ — $ 446 Contingent consideration — — 24,497 24,497 Long-term contingent consideration — — 20,605 20,605 $ — $ 446 $ 45,102 $ 45,548 Changes in the fair value of Level 3 contingent consideration for the years ended December 31, 2018 and 2017 were as follows: Contingent Consideration (in thousands) Balance at December 31, 2016 $ 38,332 Payments (1) (1,050 ) Fair value adjustment (2) 7,820 Balance at December 31, 2017 45,102 Acquisition of MiR 52,547 Foreign currency impact (3,540 ) Payments (3) (24,553 ) Fair value adjustment (4) 987 Balance at December 31, 2018 $ 70,543 (1) During the year ended December 31, 2017, Teradyne paid $1.1 million of contingent consideration for the earn-out in connection with the acquisition of Avionics Interface Technologies, LLC (“AIT”). (2) During the year ended December 31, 2017, the fair value of contingent consideration for the earn-out (3) During the year ended December 31, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out (4) During the year ended December 31, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of MiR was increased by $ 17.7 16.7 The following table provides quantitative information associated with the fair value measurement of Teradyne’s Level 3 financial instrument: Liability December 31, 2018 Fair Value Valuation Technique Unobservable Inputs Weighted Average (in thousands) Contingent consideration (MiR) $ 66,672 (1) Monte Carlo simulation Revenue volatility 18.0 % Discount rate 1.1 % Contingent consideration (Universal Robots) $ 3,871 (1) (1) Contingent consideration related to MiR and acquisitions of $31.0 million and $3.9 million, respectively, is expected to be paid in March 2019. As of December 31, 2018, the significant unobservable inputs used in the Monte Carlo simulation to fair value the MiR contingent consideration include forecasted revenues, revenue volatility, earnings before interest and taxes and discount rate. Increases or decreases in the inputs would result in a higher or lower fair value measurement. As of December 31, 2018, the maximum amount of contingent consideration that could be paid in connection with the acquisition of MiR is $115 million. The earn-out The carrying amounts and fair values of Teradyne’s financial instruments at December 31, 2018 and 2017 were as follows: December 31, 2018 December 31, 2017 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 926,752 $ 926,752 $ 429,843 $ 429,843 Marketable securities 277,827 277,827 1,473,905 1,473,905 Derivative assets 79 79 389 389 Liabilities Contingent consideration 70,543 70,543 45,102 45,102 Derivative liabilities 514 514 446 446 Convertible debt (1) 379,981 547,113 365,987 659,525 (1) The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note which includes the equity conversion features. The fair values of accounts receivable, net and accounts payable approximate the carrying amount due to the short term nature of these instruments. The following tables summarize the composition of available-for-sale marketable securities at December 31, 2018 and 2017: December 31, 2018 Available-for-Sale Fair Market Cost Unrealized Gain Unrealized (Loss) Fair Market Value Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 110,969 $ 112 $ (1,360 ) $ 109,721 $ 75,040 Commercial paper 86,130 13 (26 ) 86,117 85,094 Corporate debt securities 41,133 432 (1,545 ) 40,020 24,767 U.S. government agency securities 9,646 1 (36 ) 9,611 7,077 Certificates of deposit and time deposits 7,604 — — 7,604 — Debt mutual funds 3,153 34 — 3,187 — Non-U.S. 376 — — 376 — $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 190,100 $ 88 $ (92 ) $ 190,096 $ 140,262 Long-term marketable securities 68,911 504 (2,875 ) 66,540 51,716 $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 December 31, 2017 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 858,258 $ 72 $ (2,535 ) $ 855,795 $ 850,163 Commercial paper 283,009 18 (187 ) 282,840 258,933 Certificates of deposit and time deposits 167,523 6 (187 ) 167,342 138,340 Corporate debt securities 131,179 2,380 (373 ) 133,186 91,010 Equity and debt mutual funds 19,403 4,102 (75 ) 23,430 1,723 U.S. government agency securities 10,775 — (49 ) 10,726 10,727 Non-U.S. 582 4 — 586 — $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 1,349,970 $ 38 $ (2,029 ) $ 1,347,979 $ 1,288,844 Long-term marketable securities 120,759 6,544 (1,377 ) 125,926 62,052 $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896 As of December 31, 2018, the fair market value of investments with unrealized losses totaled $192.0 million. Of this value, $28.5 million had unrealized losses of $1.6 million greater than one year and $163.5 million had unrealized losses of $1.4 million for less than one year. As of December 31, 2017, the fair market value of investments with unrealized losses totaled $1,350.9 million. Of this value, $141.0 million had unrealized losses of $1.2 million greater than one year and $1,209.9 million had unrealized losses of $2.2 million for less than one year. Teradyne reviews its investments to identify and evaluate investments that have an indication of possible impairment. Based on this review, Teradyne determined that the unrealized losses related to these investments at December 31, 2018 and 2017, were temporary. The contractual maturities of investments in available-for-sale marketable securities held at December 31, 2018 were as follows: Cost Fair Value (in thousands) Due within one year $ 190,100 $ 190,096 Due after 1 year through 5 years 9,199 9,144 Due after 5 years through 10 years 14,081 13,405 Due after 10 years 42,478 40,804 Total $ 255,858 $ 253,449 Contractual maturities of investments is available-for-sale marketable securities held at December 31, 2018 exclude $ 3.2 million of debt mutual funds as they do not have a contractual maturity date. Derivatives Teradyne conducts business in a number of foreign countries, with certain transactions denominated in local currencies. The purpose of Teradyne’s foreign currency management is to minimize the effect of exchange rate fluctuations on certain foreign currency denominated monetary assets and liabilities. Teradyne does not use derivative financial instruments for trading or speculative purposes. To minimize the effect of exchange rate fluctuations associated with the remeasurement of monetary assets and liabilities denominated in foreign currencies, Teradyne enters into foreign currency forward contracts. The change in fair value of these derivatives is recorded directly in earnings, and is used to offset the change in value of the monetary assets and liabilities denominated in foreign currencies. At December 31, 2018 and 2017, Teradyne had the following contracts to buy and sell non-U.S. non-U.S. December 31, 2018 December 31, 2017 Buy Position Sell Position Net Total Buy Position Sell Position Net Total (in millions) Japanese Yen $ (35.0 ) $ — $ (35.0 ) $ (35.7 ) $ — $ (35.7 ) Taiwan Dollar (11.2 ) — (11.2 ) (9.9 ) — (9.9 ) Korean Won (9.6 ) — (9.6 ) (8.9 ) — (8.9 ) British Pound Sterling (1.4 ) — (1.4 ) (1.4 ) — (1.4 ) Euro — 82.2 82.2 — 27.4 27.4 Singapore Dollar — 15.7 15.7 — 33.5 33.5 Philippine Peso — 5.2 5.2 — — — Chinese Yuan — 2.8 2.8 — — — Total $ (57.2 ) $ 105.9 $ 48.7 $ (55.9 ) $ 60.9 $ 5.0 The fair value of the outstanding contracts was a loss of $0.4 million and $0.1 million, respectively, at December 31, 2018 and 2017. Gains and losses on foreign currency forward contracts and foreign currency remeasurement gains and losses on monetary assets and liabilities are included in other (income) expense, net. The following table summarizes the fair value of derivative instruments as of December 31, 2018 and 2017: Balance Sheet Location December 31, 2018 December 31, 2017 (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Prepayments $ 79 $ 389 Foreign exchange contracts Other current liabilities (514 ) (446 ) Total derivatives $ (435 ) $ (57 ) The following table summarizes the effect of derivative instruments in the statements of operations recognized for the years ended December 31, 2018, 2017, and 2016. Location of (Gains) Losses Recognized in Statement of Operations 2018 2017 2016 (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Other (income) expense, net $ 7,257 $ (1,133 ) $ 8,671 (1) The table does not reflect the corresponding gains and losses from the remeasurement of the monetary assets and liabilities denominated in foreign currencies. (2) For the years ended December 31, 2018 and 2016, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $2.4 (3) For the year ended December 31, 2017, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $2.9 million. See Note H: “Debt” regarding derivatives related to the convertible senior notes. Concentration of Credit Risk Financial instruments which potentially subject Teradyne to concentrations of credit risk consist principally of cash equivalents, marketable securities, forward currency contracts and accounts receivable. Teradyne’s cash equivalents consist primarily of money market funds invested in U.S. Treasuries and government agencies. Teradyne’s fixed income available-for-sale

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt	H. DEBT Convertible Senior Notes On December 12, 2016, Teradyne completed a private offering of $460.0 million aggregate principal amount of 1.25% convertible senior unsecured notes (the “Notes”) due December 15, 2023 and received net proceeds, after issuance costs, of approximately $450.8 million, $33.0 million of which was used to pay the net cost of the convertible note hedge transactions and $50.1 million of which was used to repurchase 2.0 million shares of Teradyne’s common stock under its existing stock repurchase program from purchasers of the Notes in privately negotiated transactions effected through one of the initial purchasers or its affiliates conducted concurrently with the pricing of the Note offering. The Notes will mature on December 15, 2023 June 15, 2017 September 15, 2023 Concurrent with the offering of the Notes, Teradyne entered into convertible note hedge transactions (the “Note Hedge Transactions”) with the initial purchasers or their affiliates (the “Option Counterparties”). The Note Hedge Transactions cover, subject to customary anti-dilution adjustments, the number of shares of the common stock that underlie the Notes, with a strike price equal to the conversion price of the Notes of $31.70. The Note Hedge Transactions cover, subject to customary anti-dilution adjustments, approximately 14.5 million shares of Teradyne’s common stock. Separately and concurrent with the pricing of the Notes, Teradyne entered into warrant transactions with the Option Counterparties (the “Warrant Transactions”) in which it sold net-share-settled (or, at its election subject to certain conditions, cash-settled) warrants to the Option Counterparties. The Warrant Transactions cover, subject to customary anti-dilution adjustments, approximately 14.5 million shares of common stock. As of December 31, 2018, the strike price of the warrants was approximately $39.78 per share. The strike price is subject to adjustment under certain circumstances. The Warrant Transactions could have a dilutive effect to Teradyne’s common stock to the extent that the market price per share of Teradyne’s common stock, as measured under the terms of the Warrant Transactions, exceeds the applicable strike price of the warrants. The Note Hedge Transactions are expected to reduce the potential dilution to Teradyne’s common stock upon any conversion of the Notes. However, the Warrant Transactions could separately have a dilutive effect to the extent that the market value per share of Teradyne’s common stock exceeds the applicable strike price of the warrant. The net cost of the Note Hedge Transactions, after being partially offset by the proceeds from the sale of the warrants, was approximately $33.0 million. In connection with establishing their initial hedge of these convertible note hedge and warrant transactions, the Option Counterparties have entered into various derivative transactions with respect to Teradyne’s common stock and/or purchased shares of Teradyne’s common stock or other securities, including the Notes, concurrent with, or shortly after, the pricing of the Notes. In addition, the Option Counterparties may modify their hedge positions by entering into or unwinding various derivative transactions with respect to Teradyne’s common stock or by selling Teradyne’s common stock or other securities, including the Notes, in secondary market transactions (and may do so during any observation period related to the conversion of the Notes). These activities could adversely affect the value of Teradyne’s common stock and the Notes. Teradyne considered the guidance of ASC 815-40, “Derivatives and Hedging—Contracts in Entity’s Own Equity,” and concluded that the convertible note hedge is both indexed to Teradyne’s stock and should be classified in stockholders’ equity in its statements of financial position. The convertible note hedge is considered indexed to Teradyne’s stock as the terms of the Note Hedge Transactions do not contain an exercise contingency and the settlement amount equals the difference between the fair value of a fixed number of Teradyne’s shares and a fixed strike price. Because the only variable that can affect the settlement amount is Teradyne’s stock price, which is an input to the fair value of a fixed-for-fixed option contract, the convertible note hedge is considered indexed to Teradyne’s stock. Teradyne assessed whether the convertible note hedge should be classified as equity under ASC 815-40. In the Note Hedge Transactions contract the settlement terms permit net cash settlement or net share settlement, at the option of Teradyne. Therefore, the criteria as set forth in ASC 815-40 were evaluated by Teradyne. In reviewing the criteria, Teradyne noted the following: (1) the convertible note hedge does not require Teradyne to issue shares; (2) there is no requirement to net cash settle the convertible note hedge for failure to make timely filings with the SEC; (3) in the case of termination, the convertible note hedge is settled in the same consideration as the holders of the underlying stock; (4) the counterparty does not have rights that rank higher than those of a shareholder of the stock underlying the convertible note hedge; and (5) there is no requirement to post collateral. Based on its analysis of those criteria, Teradyne concluded that the convertible note hedge should be recorded in equity and no further adjustment should be made in future periods to adjust the value of the convertible note hedge. Teradyne analyzed the Warrant Transactions under ASC 815-40, “Derivatives and Hedging—Contracts in Entity’s Own Equity,” and other relevant literature, and determined that it met the criteria for classification as an equity transaction and is considered indexed to Teradyne’s stock. As a result, Teradyne recorded the proceeds from the warrants as an increase to additional paid-in capital. Teradyne does not recognize subsequent changes in fair value of the warrants in its financial statements. The provisions of ASC 470-20, “ Debt with Conversion and Other Options, ” are applicable to the Notes. ASC 470-20 requires Teradyne to separately account for the liability (debt) and equity (conversion feature) components of the Notes in a manner that reflects Teradyne’s nonconvertible debt borrowing rate at the date of issuance when interest cost is recognized in subsequent periods. Teradyne allocated $100.8 million of the $460.0 million principal amount of the Notes to the equity component, which represents a discount to the debt and will be amortized to interest expense using the effective interest method through December 2023. Accordingly, Teradyne’s effective annual interest rate on the Notes will be approximately 5.0%. The Notes are classified as long-term debt in the balance sheet based on their December 15, 2023 maturity date. Debt issuance costs of approximately $7.2 million are being amortized to interest expense using the effective interest method over the seven year term of the Notes. As of December 31, 2018, debt issuance costs were approximately $5.3 million. The below tables represents the key components of Teradyne’s convertible senior notes: December 31, 2018 December 31, 2017 (in thousands) Debt principal $ 460,000 $ 460,000 Unamortized discount 80,019 94,013 Net carrying amount of convertible debt $ 379,981 $ 365,987 For the year ended December 31, 2018 December 31, 2017 (in thousands) Contractual interest expense on the coupon $ 5,750 $ 5,734 Amortization of the discount component and debt issue fees recognized as interest expense 13,995 13,318 Total interest expense on the convertible debt $ 19,745 $ 19,052 As of December 31, 2018, the unamortized discount was $80.0 million, which will be amortized over five years using the effective interest rate method. The carrying amount of the equity component was $100.8 million. As of December 31, 2018, the conversion price was approximately $31.70 per share and if converted the value of the notes was $455.4 million. Revolving Credit Facility On April 27, 2015, Teradyne entered into a Credit Agreement (the “Credit Agreement”) with Barclays Bank PLC, as administrative agent and collateral agent, and the lenders party thereto. The Credit Agreement provides for a five-year, senior secured revolving credit facility of up to $350 million (the “Credit Facility”). The Credit Agreement further provides that, subject to customary conditions, Teradyne may seek to obtain from existing or new lenders incremental commitments under the Credit Facility in an aggregate principal amount not to exceed $150 million. Proceeds from the Credit Facility may be used for general corporate purposes and working capital. Teradyne incurred $2.3 million in costs related to the revolving credit facility. These costs are being amortized over the five-year term of the revolving credit facility and are included in interest expense in the statements of operations. As of March 1, 2019, Teradyne has not borrowed any funds under the Credit Facility. The interest rates applicable to loans under the Credit Facility are, at Teradyne’s option, equal to either a base rate plus a margin ranging from 0.00% to 1.00% per annum or LIBOR plus a margin ranging from 1.00% to 2.00% per annum, based on the Consolidated Leverage Ratio of Teradyne and its Restricted Subsidiaries. In addition, Teradyne will pay a commitment fee on the unused portion of the commitments under the Credit Facility ranging from 0.125% to 0.350% per annum, based on the then applicable Consolidated Leverage Ratio. Teradyne is not required to repay any loans under the Credit Facility prior to maturity, subject to certain customary exceptions. Teradyne is permitted to prepay all or any portion of the loans under the Credit Facility prior to maturity without premium or penalty, other than customary LIBOR breakage costs. The Credit Agreement contains customary events of default, representations, warranties and affirmative and negative covenants that, among other things, limit Teradyne’s and its Restricted Subsidiaries’ ability to sell assets, grant liens on assets, incur other secured indebtedness and make certain investments and restricted payments, all subject to exceptions set forth in the Credit Agreement. The Credit Agreement also requires Teradyne to satisfy two financial ratios measured as of the end of each fiscal quarter: a consolidated leverage ratio and an interest coverage ratio. As of December 31, 2018, Teradyne was in compliance with all covenants. The Credit Facility is guaranteed by certain of Teradyne’s domestic subsidiaries and collateralized by assets of Teradyne and such subsidiaries, including a pledge of 65% of the capital stock of certain foreign subsidiaries.

Accumulated Other Comprehensive

Accumulated Other Comprehensive (Loss) Income	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive (Loss) Income	I. ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME Changes in accumulated other comprehensive (loss) income, which is presented net of tax, consist of the following: Foreign Currency Translation Adjustment Unrealized Gains on Marketable Securities Retirement Plans Prior Service Credit Total (in thousands) Balance at December 31, 2016, net of tax of $0, $209, $(778) $ (21,921 ) $ (60 ) $ 1,767 $ (20,214 ) Other comprehensive income before reclassifications, net of tax of $0, $1,903, $0 37,840 1,863 — 39,703 Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(297), $(154) — (441 ) (272 ) (713 ) Net current period other comprehensive income, net of tax of $0, $1,606, $(154) 37,840 1,422 (272 ) 38,990 Balance at December 31, 2017, net of tax of $0, $1,815, $(932) 15,919 1,362 1,495 18,776 Other comprehensive loss before reclassifications, net of tax of $0, $(722), $0 (28,442 ) (2,110 ) — (30,552 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(21), $(71) — 1,337 (245 ) 1,092 Net current period other comprehensive loss, net of tax of $0, $(743), $(71) (28,442 ) (773 ) (245 ) (29,460 ) Reclassification of tax effects resulting from the Tax Reform Act, net of tax of $0, $(691), $(78), respectively (a) — 691 78 769 Reclassification of unrealized gains on equity securities, net of tax of $0, $(902), $0, respectively, (b) — (3,125 ) — (3,125 ) Balance at December 31, 2018, net of tax of $0, $(521), $(1,081) $ (12,523 ) $ (1,845 ) $ 1,328 $ (13,040 ) (a) In the year ended December 31, 2018, Teradyne early adopted ASU 2018-02, “Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” As a result, the stranded tax effects resulting from the Tax Reform Act enacted in December 2017 were reclassified from accumulated other comprehensive income to retained earnings. (b) In the year ended December 31, 2018, Teradyne adopted ASU 2016-01, “ Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities .” See Note B: “Accounting Policies.” Reclassifications out of accumulated other comprehensive income to the statements of operations for the years ended December 31, 2018, 2017, and 2016 were as follows: Details about Accumulated Components For the year ended Affected Line Item in the Statements of Operations December 31, 2018 December 31, 2017 December 31, 2016 (in thousands) Available-for-sale marketable securities Unrealized (losses) gains, net of tax of $21, $297, $255 $ (1,337 ) $ 441 $ 683 Interest income (expense) Defined benefit pension and postretirement plans: Amortization of prior service benefit, net of tax of $71, $154, $190 245 272 321 (a) Total reclassifications, net of tax of $92, $451, $445 $ (1,092 ) $ 713 $ 1,004 Net income (a) The amortization of prior service credit is included in the computation of net periodic pension cost and postretirement benefit; see Note N: “Retirement Plans.”

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets	J. GOODWILL AND INTANGIBLE ASSETS Goodwill Teradyne performs its annual goodwill impairment test as required under the provisions of ASC 350-10, Intangibles—Goodwill and Other, Teradyne has the option to perform a qualitative assessment (“Step zero”) to determine whether it is more likely than not two-step more likely than not two-step two-step In the second quarter of 2016, the Wireless Test reporting unit (which is Teradyne’s Wireless Test operating and reportable segment) reduced headcount by 11% as a result of a sharp decline in projected demand attributable to an estimated smaller future wireless test market. The decrease in projected demand was due to lower forecasted buying from Teradyne’s largest Wireless Test segment customer (who has contributed between 51% and 73% of annual Wireless Test sales since the LitePoint acquisition in 2011 through 2015) as a result of the customer’s numerous operational efficiencies; slower smartphone growth rates; and a slowdown of new wireless technology adoption. Teradyne considered the headcount reduction and sharp decline in projected demand to be a triggering event for an interim goodwill impairment test. Teradyne allocated the fair value of the Wireless Test reporting unit to all of its assets and liabilities (including unrecognized intangible assets). The net book value of raw materials inventory was estimated as an approximation of current replacement costs. The fair value of finished goods inventory was estimated at the present value of selling price less direct selling costs and profit on the selling effort. The selling price used in the inventory fair values was based upon the product gross margins included in Teradyne’s forecast. The fair value of the deferred revenue liability was estimated by assessing the costs required to service the obligation plus a reasonable profit margin. The fair value for personal property assets, which consisted of furniture and fixtures, machinery and equipment, computer equipment, software and leasehold improvements, was estimated using the replacement cost approach, which approximated carrying value. The fair value of intangible assets was estimated using the income approach and, in particular, developed technology and trademarks/trade names were valued using the relief-from-royalty method and customer relationships and customer backlog were valued using the discounted cash flow method. Royalty rates were estimated using rates applicable to wireless testing equipment and other similar technologies. Based upon this allocation, Teradyne determined that the Wireless Test reporting unit goodwill is valued at $8.0 million and recorded an impairment loss of $254.9 million in the second quarter of 2016. In the fourth quarter of 2018, Teradyne performed the annual goodwill impairment test. Teradyne completed step one of the two-step In the fourth quarter of 2017, Teradyne performed the annual goodwill impairment test. Teradyne completed step one of the two-step In the fourth quarter of 2016, Teradyne performed the annual goodwill impairment test. Teradyne completed step one of the two-step The changes in the carrying amount of goodwill by reportable segments for the years ended December 31, 2018 and 2017 are as follows: Industrial Automation System Test Wireless Test Semiconductor Test Total (in thousands) Balance at December 31, 2016: Goodwill $ 204,851 $ 158,699 $ 361,819 $ 260,540 $ 985,909 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 204,851 10,516 7,976 — 223,343 Foreign currency translation adjustment 28,668 — — — 28,668 Balance at December 31, 2017: Goodwill 233,519 158,699 361,819 260,540 1,014,577 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 233,519 10,516 7,976 — 252,011 MiR acquisition 135,976 — — — 135,976 Energid acquisition 14,394 — — — 14,394 Foreign currency translation adjustment (20,531 ) — — — (20,531 ) Balance at December 31, 2018: Goodwill 363,358 158,699 361,819 260,540 1,144,416 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) $ 363,358 $ 10,516 $ 7,976 $ — $ 381,850 Intangible Assets Teradyne reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable or that the useful lives of these assets are no longer appropriate. As a result of the Wireless Test segment goodwill impairment review in the second quarter of 2016, Teradyne performed an impairment test of the Wireless Test segment’s intangible and long-lived assets. The impairment test is based on a comparison of the estimated undiscounted cash flows to the carrying value of the asset group. If undiscounted cash flows for the asset group are less than the carrying amount, the asset group is written down to its estimated fair value based on a discounted cash flow analysis. The cash flow estimates used to determine the impairment contain management’s best estimates using appropriate assumptions and projections at that time. The fair value of intangible assets was estimated using the income approach and, in particular, developed technology and trademarks/trade names were valued using the relief-from-royalty method and customer relationships were valued using the discounted cash flow method. Royalty rates were estimated using rates applicable to wireless testing equipment and other similar technologies. As a result of the analysis, Teradyne recorded an $83.3 million impairment charge in the second quarter of 2016 in acquired intangible assets impairment on the statements of operations, resulting in a remaining intangible assets balance of $2.2 million at December 31, 2018 for the Wireless Test segment. There were no events or circumstances indicating that the carrying value of intangible and long-lived assets may not be recoverable in 2018 and 2017. Amortizable intangible assets consist of the following and are included in intangible assets, net on the balance sheets: December 31, 2018 Gross Carryin Amount (1)(2) Accumulated Amortization (2) Foreign Currency Translation Adjustment Net Carrying Amount (in thousan ds) Developed technology $ 336,308 $ (252,080 ) $ (4,079 ) $ 80,149 Customer relationships 97,153 (83,448 ) (340 ) 13,365 Tradenames and trademarks 64,420 (31,653 ) (799 ) 31,968 Non-compete agreement 320 (320 ) — — Backlog 30 (30 ) — — Total intangible assets $ 498,231 $ (367,531 ) $ (5,218 ) $ 125,482 December 31, 2017 Gross Carrying Amount Accumulated Amortization Foreign Currency Translation Adjustment Net Carrying Amount (in thousands) Developed technology $ 270,877 $ (226,190 ) $ 1,618 $ 46,305 Customer relationships 92,741 (83,585 ) 171 9,327 Tradenames and trademarks 50,100 (27,120 ) 416 23,396 Non-compete agreement 320 (260 ) — 60 Total intangible assets $ 414,038 $ (337,155 ) $ 2,205 $ 79,088 (1) Includes intangible assets acquired in 2018, $80.7 million from the MiR acquisition and $12.3 million from the Energid acquisition. (2) In 2018, $8.8 million of amortizable intangible assets became fully amortized and have been eliminated from the gross carrying amount and accumulated amortization. Aggregate intangible assets amortization expense for the years ended December 31, 2018, 2017, and 2016 was $39.2 million, $30.5 million, and $52.6 million, respectively. Estimated intangible assets amortization expense for each of the five succeeding fiscal years is as follows: Year Amortization Expense (in thousands) 2019 $ 38,496 2020 24,186 2021 13,945 2022 13,052 2023 12,785 Thereafter 23,018

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies	K. COMMITMENTS AND CONTINGENCIES Purchase Commitments As of December 31, 2018, Teradyne had entered into non-cancelable Commitments Teradyne leases certain of its office buildings and other facilities under various operating lease arrangements that include renewal options and escalation clauses for adjusting rent payments to reflect changes in price indices. Rental expense for leases with fixed escalation clauses is recognized on a straight line basis over the lease term. Rental expense for the years ended December 31, 2018, 2017, and 2016 was $19.3 million, $20.2 million, and $19.1 million, respectively. The following table reflects Teradyne’s non-cancelable Non-cancelable Lease Commitments (in thousands) 2019 $ 19,570 2020 18,293 2021 13,578 2022 9,693 2023 5,449 Beyond 2024 9,472 Total $ 76,055 Legal Claims Teradyne is subject to legal proceedings, claims and investigations that arise in the ordinary course of business such as, but not limited to, patent, employment, commercial and environmental matters. Teradyne believes that it has meritorious defenses against all pending claims and intends to vigorously contest them. While it is not possible to predict or determine the outcomes of any pending claims or to provide possible ranges of losses that may arise, Teradyne believes the potential losses associated with all of these actions are unlikely to have a material adverse effect on its business, financial position or results of operations. Guarantees and Indemnification Obligations Teradyne provides indemnification, to the extent permitted by law, to its officers, directors, employees and agents for liabilities arising from certain events or occurrences while the officer, director, employee, or agent, is or was serving, at Teradyne’s request in such capacity. Teradyne has entered into indemnification agreements with certain of its officers and directors. With respect to acquisitions, Teradyne provides indemnifications to or assumes indemnification obligations for the current and former directors, officers and employees of the acquired companies in accordance with the acquired companies’ by-laws Teradyne enters into agreements in the ordinary course of business with customers, resellers, distributors, integrators and suppliers. Most of these agreements require Teradyne to defend and/or indemnify the other party against intellectual property infringement claims brought by a third party with respect to Teradyne’s products. From time to time, Teradyne also indemnifies customers and business partners for damages, losses and liabilities they may suffer or incur relating to personal injury, personal property damage, product liability, breach of confidentiality obligations and environmental claims relating to the use of Teradyne’s products and services or resulting from the acts or omissions of Teradyne, its employees, authorized agents or subcontractors. On occasion, Teradyne has also provided guarantees to customers regarding the delivery and performance of its products in addition to the warranty described below. As a matter of ordinary business course, Teradyne warrants that its products will substantially perform in accordance with its standard published specifications in effect at the time of delivery. Most warranties have a one-year In addition, in the ordinary course of business, Teradyne provides minimum purchase guarantees to certain vendors to ensure continuity of supply against the market demand. Although some of these guarantees provide penalties for cancellations and/or modifications to the purchase commitments as the market demand decreases, most of the guarantees do not. Therefore, as the market demand decreases, Teradyne re-evaluates With respect to its agreements covering product, business or entity divestitures and acquisitions, Teradyne provides certain representations, warranties and covenants to purchasers and agrees to indemnify and hold such purchasers harmless against breaches of such representations, warranties and covenants. Many of the indemnification claims have a definite expiration date while some remain in force indefinitely. With respect to its acquisitions, Teradyne may, from time to time, assume the liability for certain events or occurrences that took place prior to the date of acquisition. As a matter of ordinary course of business, Teradyne occasionally guarantees certain indebtedness obligations of its subsidiary companies, limited to the borrowings from financial institutions, purchase commitments to certain vendors, and lease commitments to landlords. Based on historical experience and information known as of December 31, 2018 and 2017, except for product warranty, Teradyne has not recorded any liabilities for these guarantees and obligations because the amount would be immaterial.

Net Income (Loss) per Common Sh

Net Income (Loss) per Common Share	12 Months Ended
	Dec. 31, 2018
Net Income (Loss) per Common Share	L. NET INCOME (LOSS) PER COMMON SHARE The following table sets forth the computation of basic and diluted net income (loss) per common share: 2018 2017 2016 (in thousands, except per share amounts) Net income (loss) for basic and diluted net income per share $ 451,779 $ 257,692 $ (43,421 ) Weighted average common shares-basic 187,672 198,069 202,578 Effect of dilutive potential common shares: Incremental shares from assumed conversion of convertible notes (1) 2,749 1,298 — Convertible note hedge warrant shares (2) 485 112 — Restricted stock units 1,385 1,800 — Stock options 278 335 0 Employee stock purchase rights 36 27 0 Dilutive potential common shares 4,933 3,572 — Weighted average common shares-diluted 192,605 201,641 202,578 Net income (loss) per common share-basic $ 2.41 $ 1.30 $ (0.21 ) Net income (loss) per common share-diluted $ 2.35 $ 1.28 $ (0.21 ) (1) Incremental shares from the assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.70, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period. (2) Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.78, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period. The computation of diluted net income per common share for 2018 excludes the effect of the potential exercise of stock options to purchase approximately 0.1 The computation of diluted net income per common share for 2017 excludes the effect of the potential exercise of stock options to purchase approximately 0.1 million shares because the effect would have been anti-dilutive. The computation of diluted net loss per common share for 2016 excludes the effect of the potential exercise of all outstanding stock options and restricted stock units because Teradyne had a net loss and inclusion would be anti-dilutive.

Restructuring and Other

Restructuring and Other	12 Months Ended
	Dec. 31, 2018
Restructuring and Other	M. RESTRUCTURING AND OTHER During the year ended December 31, 2018, Teradyne recorded an expense of $17.7 million for the increase in the fair value of the MiR contingent consideration liability, $8.7 million of severance charges related to headcount reductions primarily in Semiconductor Test, and $4.5 million for acquisition related expenses and compensation, partially offset by a gain of $16.7 million for the decrease in the fair value of the Universal Robots contingent consideration liability. During the year ended December 31, 2017, Teradyne recorded an expense of $7.8 million for the increase in the fair value of the Universal Robots contingent consideration liability, $3.8 million of severance charges related to headcount reductions primarily in Semiconductor Test, $1.1 million for an impairment of fixed assets in Semiconductor Test, $1.0 million for a lease impairment of a Wireless Test facility in Sunnyvale, CA, which was terminated in September 2017, and $0.8 million of expenses related to an earthquake in Kumamoto, Japan, partially offset by $5.1 million of property insurance recovery related to the Japan earthquake. During the year ended December 31, 2016, Teradyne recorded an expense of $15.9 million for the increase in the fair value of the contingent consideration liability, of which $15.3 million was related to Universal Robots and $0.6 million was related to AIT, $6.0 million of severance charges related to headcount reductions primarily in Wireless Test, $4.2 million for an impairment of fixed assets, and $0.9 million for expenses related to an earthquake in Kumamoto, Japan, partially offset by $5.1 million of property insurance recovery related to the Japan earthquake.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2018
Defined Benefit Pension Plans
Retirement Plans	N. RETIREMENT PLANS ASC 715 , Compensation—Retirement Benefits, Defined Benefit Pension Plans Teradyne has defined benefit pension plans covering a portion of domestic employees and employees of certain non-U.S. During 2018, Teradyne purchased a group annuity contract for its retiree participants in the U.S. qualified pension plan. Under the group annuity, the accrued pension obligations for approximately 1,700 retiree participants were transferred to an insurance company. The reduction in the pension benefit obligation and pension assets was $151.3 million. During 2018, Teradyne recorded a settlement loss of $0.3 million related to the retiree group annuity transaction. The December 31 balances of these defined benefit pension plans assets and obligations are shown below: 2018 2017 United States Foreign United States Foreign (in thousands) Assets and Obligations Change in benefit obligation: Projected benefit obligation: Beginning of year $ 363,026 $ 39,353 $ 353,616 $ 60,738 Service cost 2,196 786 2,239 818 Interest cost 8,940 687 13,151 852 Actuarial (gain) loss (30,136 ) 773 12,702 262 Benefits paid (14,793 ) (741 ) (18,682 ) (994 ) Retiree annuity purchase (151,341 ) — — — Liability loss due to settlement 345 — — — Settlements — — — (28,560 ) Admin expenses paid — — — (40 ) Non-U.S. — (1,712 ) — 6,277 End of year 178,237 39,146 363,026 39,353 Change in plan assets: Fair value of plan assets: Beginning of year 324,506 1,307 307,304 27,571 Company contributions 2,587 822 4,462 883 Actual return on plan assets (16,658 ) 50 31,422 737 Benefits paid (14,793 ) (741 ) (18,682 ) (994 ) Retiree annuity purchase (151,341 ) — — — Settlements — — — (28,560 ) Admin expenses paid — — — (40 ) Non-U.S. — (38 ) — 1,710 End of year 144,301 1,400 324,506 1,307 Funded status $ (33,936 ) $ (37,746 ) $ (38,520 ) $ (38,046 ) The following table provides amounts recorded within the account line items of the statements of financial position as of December 31: 2018 2017 United States Foreign United States Foreign (in thousands) Retirement plans assets $ 16,883 $ — $ 17,491 $ — Accrued employees’ compensation and withholdings (2,676 ) (852 ) (2,524 ) (863 ) Retirement plans liabilities (48,143 ) (36,894 ) (53,487 ) (37,183 ) Funded status $ (33,936 ) $ (37,746 ) $ (38,520 ) $ (38,046 ) The following table provides amounts recognized in accumulated other comprehensive income as of December 31: 2018 2017 United States Foreign United States Foreign (in thousands) Prior service cost, before tax $ — $ — $ 58 $ — Deferred taxes 560 — 539 — Total recognized in other comprehensive income, net of tax $ 560 $ — $ 597 $ — The accumulated benefit obligation for the United States defined benefit pension plans was $172.8 million and $354.3 million at December 31, 2018 and 2017, respectively. The accumulated benefit obligation for foreign defined benefit pension plans was $35.6 million and $34.7 million at December 31, 2018 and 2017, respectively. Information for pension plans with an accumulated benefit obligation in excess of plan assets as of December 31: 2018 2017 United States Foreign United States Foreign (in millions) Projected benefit obligation $ 50.8 $ 39.1 $ 56.0 $ 39.4 Accumulated benefit obligation 48.6 35.6 51.6 34.7 Fair value of plan assets — 1.4 — 1.3 Expense For the years ended December 31, 2018, 2017, and 2016, Teradyne’s net periodic pension (income) cost was comprised of the following: 2018 2017 2016 United States Foreign United States Foreign United States Foreign (in thousands) Components of Net Periodic Pension (Income) Cost: Service cost $ 2,196 $ 786 $ 2,239 $ 818 $ 2,302 $ 761 Interest cost 8,940 687 13,151 852 13,630 1,185 Expected return on plan assets (9,049 ) (19 ) (12,008 ) (165 ) (13,830 ) (443 ) Amortization of prior service cost 58 — 70 — 96 — Net actuarial (gain) loss (4,429 ) 743 (6,712 ) (310 ) (4,013 ) 815 Settlement loss 345 — — — — — Total net periodic pension (income) cost $ (1,939 ) $ 2,197 $ (3,260 ) $ 1,195 $ (1,815 ) $ 2,318 Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Reversal of amortization items: Prior service cost (58 ) — (70 ) — (96 ) — Total recognized in other comprehensive income (58 ) — (70 ) — (96 ) — Total recognized in net periodic pension (income) cost and other comprehensive income $ (1,997 ) $ 2,197 $ (3,330 ) $ 1,195 $ (1,911 ) $ 2,318 Weighted Average Assumptions to Determine Net Periodic Pension Cost at January 1: 2018 2017 2016 United States Foreign United States Foreign United States Foreign Discount rate 3.4 % 1.8 % 3.9 % 1.8 % 4.0 % 2.3 % Expected return on plan assets 4.3 1.5 4.0 2.0 4.8 2.0 Salary progression rate 2.3 2.7 2.6 2.7 2.7 3.2 Weighted Average Assumptions to Determine Pension Obligations at December 31: 2018 2017 United States Foreign United States Foreign Discount rate 4.1 % 1.8 % 3.4 % 1.8 % Salary progression rate 2.3 2.6 2.3 2.7 In developing the expected return on plan assets assumption, Teradyne evaluates input from its investment manager and pension consultants, including their forecast of asset class return expectations. Teradyne believes that 4.25% was an appropriate rate to use for fiscal 2018 for the U.S. Qualified Pension Plan (“U.S. Plan”). Teradyne recognizes net actuarial gains and losses and the change in the fair value of the plan assets in its operating results in the year in which they occur or upon any interim remeasurement of the plans. Teradyne calculates the expected return on plan assets using the fair value of the plan assets. Actuarial gains and losses are generally measured annually as of December 31 and, accordingly, recorded during the fourth quarter of each year or upon any interim remeasurement of the plans. The discount rate utilized to determine future pension obligations for the U.S. Plan is based on FTSE Pension Index adjusted for the plan’s expected cash flows and was 4.15% at December 31, 2018, up from 3.4% at December 31, 2017. Plan Assets As of December 31, 2018, the fair value of Teradyne’s pension plans’ assets totaled $145.7 million of which $144.3 million was related to the U.S. Plan and $1.4 million was related to the Taiwan defined benefit pension plan. Substantially all of Teradyne’s pension plans’ assets are held in individual trusts, which were established for the investment of assets of Teradyne’s sponsored retirement plans. The following table provides weighted average pension asset allocation by asset category at December 31, 2018 and 2017: 2018 2017 United States Foreign United States Foreign Fixed income securities 94.0 % — % 88.1 % — % Equity securities 5.0 — 9.9 — Other 1.0 100.0 2.0 100.0 100.0 % 100.0 % 100.0 % 100.0 % The assets of the U.S. Plan are overseen by the Teradyne Fiduciary Committee which is comprised of members of senior management drawn from appropriate diversified levels of the management team. The Fiduciary Committee is responsible for setting the policy that provides the framework for management of the U.S. Plan assets. In accordance with its responsibilities, the Fiduciary Committee meets on a regular basis to review the performance of the U.S. Plan assets and compliance with the investment policy. The policy sets forth an investment structure for managing U.S. Plan assets, including setting the asset allocation ranges, which are expected to provide an appropriate level of overall diversification required to maximize the long-term return on plan assets for a prudent and reasonable level of risk given prevailing market conditions, total investment return over the long term, and preservation of capital, while maintaining sufficient liquidity to pay the benefits of the U.S. Plan. The investment portfolio will not, at any time, have a direct investment in Teradyne stock. It may have indirect investment in Teradyne stock, if one of the funds selected by the investment manager invests in Teradyne stock. In developing the asset allocation ranges, third party asset allocation studies are periodically performed that consider the current and expected positions of the plan assets and funded status. Based on this study and other appropriate information, the Fiduciary Committee establishes asset allocation ranges taking into account acceptable risk targets and associated returns. The investment return objectives are to avoid excessive volatility and produce a rate of return that at least matches the Policy Index identified below. The manager’s investment performance is reviewed at least annually. Results for the total portfolio and for each major category of assets are evaluated in comparison with appropriate market indices and the Policy Index. The target asset allocation and the index for each asset category for the U.S. Plan, per the investment policy, are as follows: Asset Category: Policy Index: Target Allocation U.S. corporate fixed income Barclays U.S. Corporate A or Better Index 75 % Global equity MSCI World Minimum Volatility Index 5 U.S. government fixed income Barclays Index 14 High yield fixed income Barclays U.S. Corporate High Yield 2% Issuer Cap Index 5 Cash Citigroup Three Month U.S. Treasury Bill Index 1 Teradyne’s U.S. Plan invests primarily in common trust funds. Units held in the common trust funds are valued at the unit price as reported by the investment manager based on the asset value of the underlying investments; underlying investments in equity securities are valued at the last reported sales price, and underlying investments in fixed-income securities are generally valued using methods based upon market transactions for comparable securities. In 2017, the U.K. defined benefit pension was terminated and the obligations and assets of the plan were transferred to an insurance company. During the year ended December 31, 2018, $2.7 million of pension assets were transferred out of Level 3 to Level 2. During the year ended December 31, 2017, there were no transfers of pension assets in or out of Level 1, Level 2 or Level 3. The fair value of pension plan assets by asset category and by level at December 31, 2018 and December 31, 2017 were as follows: December 31, 2018 United States Foreign Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in thousands) Fixed income securities: Corporate debt securities $ — $ 115,424 $ — $ 115,424 $ — $ — $ — $ — U.S. government securities — 20,176 — 20,176 — — — — Global equity — 7,252 — 7,252 — — — — Other — — — — — 1,400 — 1,400 Cash and cash equivalents 1,449 — — 1,449 — — — — Total $ 1,449 $ 142,852 $ — $ 144,301 $ — $ 1,400 $ — $ 1,400 December 31, 2017 United States Foreign Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in thousands) Fixed income securities: Corporate debt securities $ — $ 260,294 $ — $ 260,294 $ — $ — $ — $ — U.S. government securities — 25,709 — 25,709 — — — — Global equity — 32,120 — 32,120 — — — — Group annuity insurance contracts — — 3,166 3,166 — — — — Other — — — — — 1,307 — 1,307 Cash and cash equivalents 3,217 — — 3,217 — — — — Total $ 3,217 $ 318,123 $ 3,166 $ 324,506 $ — $ 1,307 $ — $ 1,307 The pension plan assets identified as Level 3 above are related to group annuity insurance contracts held by the U.S. Plan. Changes in the fair value of Level 3 group annuity insurance contracts for the years ended December 31, 2018 and 2017 were as follows: Group Annuity Insurance Contracts (in thousands) Balance at December 31, 2016 $ 29,456 Settlements (28,560 ) Interest and market value adjustments 959 Benefits paid (244 ) Other (61 ) Non-U.S. 1,616 Balance at December 31, 2017 3,166 Transfer out of Level 3 (2,658 ) Purchases of retiree annuity insurance contracts (512 ) Interest and market value adjustments 59 Benefits paid (40 ) Other (15 ) Balance at December 31, 2018 $ — Contributions Teradyne’s funding policy is to make contributions to the plans in accordance with local laws and to the extent that such contributions are tax deductible. During 2018, Teradyne contributed $2.6 million to the U.S. supplemental executive defined benefit pension plan and $0.8 million to certain qualified plans for non-U.S. non-U.S. non-U.S. Future benefit payments are expected to be paid as follows: United States Foreign (in thousands) 2019 $ 6,903 $ 874 2020 7,133 1,522 2021 8,026 905 2022 8,863 888 2023 9,584 1,199 2024-2028 57,120 5,921 Postretirement Benefit Plans In addition to receiving pension benefits, U.S. Teradyne employees who meet early retirement eligibility requirements as of their termination dates may participate in Teradyne’s Welfare Plan, which includes medical and dental benefits up to age 65. Death benefits provide a fixed sum to retirees’ survivors and are available to all retirees. Substantially all of Teradyne’s current U.S. employees could become eligible for these benefits, and the existing benefit obligation relates primarily to those employees. The December 31 balances of the postretirement assets and obligations are shown below: 2018 2017 (in thousands) Assets and Obligations Change in benefit obligation: Projected benefit obligation: Beginning of year $ 6,177 $ 5,510 Service cost 39 34 Interest cost 196 201 Actuarial loss 25 398 Special termination benefits 3,708 591 Benefits paid (889 ) (557 ) End of year 9,256 6,177 Change in plan assets: Fair value of plan assets: Beginning of year — — Company contributions 889 557 Benefits paid (889 ) (557 ) End of year — — Funded status $ (9,256 ) $ (6,177 ) The following table provides amounts recorded within the account line items of financial position as of December 31: 2018 2017 (in thousands) Accrued employees’ compensation and withholdings $ (1,310 ) $ (591 ) Retirement plans liability (7,946 ) (5,586 ) Funded status $ (9,256 ) $ (6,177 ) The following table provides amounts recognized in accumulated other comprehensive income as of December 31: 2018 2017 (in thousands) Prior service credit, before tax $ (249 ) $ (622 ) Deferred taxes (1,641 ) (1,472 ) Total recognized in other comprehensive income, net of tax $ (1,890 ) $ (2,094 ) The estimated portion of prior service credit remaining in accumulated other comprehensive income that is expected to be recognized as a component of net periodic postretirement benefit income in 2019 is $(0.2) million. Expense For the years ended December 31, 2018, 2017, and 2016, Teradyne’s net periodic postretirement benefit cost (income) was comprised of the following: 2018 2017 2016 (in thousands) Components of Net Periodic Postretirement Benefit Cost (income): Service cost $ 39 $ 34 $ 37 Interest cost 196 201 218 Amortization of prior service credit (373 ) (496 ) (607 ) Net actuarial loss 25 398 5 Special termination benefits 3,708 591 — Total net periodic postretirement benefit cost (income) 3,595 728 (347 ) Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Prior service cost — — (93 ) Reversal of amortization items: Prior service credit 373 496 607 Total recognized in other comprehensive income 373 496 514 Total recognized in net periodic postretirement benefit cost (income) and other comprehensive income $ 3,968 $ 1,224 $ 167 Weighted Average Assumptions to Determine Net Periodic Postretirement Benefit Income as of January 1: 2018 2017 2016 Discount rate 3.4 % 3.9 % 3.9 % Initial health care cost trend rate 7.9 7.3 7.5 Ultimate health care cost trend rate 4.5 5.0 5.0 Year in which ultimate health care cost trend rate is reached 2026 2023 2023 Weighted Average Assumptions to Determine Postretirement Benefit Obligation as of December 31: 2018 2017 2016 Discount rate 4.0 % 3.4 % 3.9 % Initial medical trend 7.5 7.9 7.3 Ultimate health care trend 4.5 4.5 5.0 Medical cost trend rate decrease to ultimate rate in year 2026 2026 2023 Assumed health care trend rates could have a significant effect on the amounts reported for health care plans. A one percentage point change in the assumed health care cost trend rates for the year ended December 31, 2018 would have the following effects: 1 Percentage Point Increase 1 Percentage Point Decrease (in thousands) Effect on total service and interest cost components $ 7 $ (7 ) Effect on postretirement benefit obligations 181 (171 ) Expected Future Benefit Payments Future benefit payments are expected to be paid as follows: Benefit Payments (in thousands) 2019 $ 1,310 2020 1,234 2021 1,181 2022 984 2023 811 2024-2028 2,364

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Stock-Based Compensation	O. STOCK-BASED COMPENSATION Stock Compensation Plans Under Teradyne’s stock compensation plans, Teradyne grants stock options, restricted stock units and performance-based restricted stock units, and employees are eligible to purchase Teradyne’s common stock through its Employee Stock Purchase Plan (“ESPP”). Stock options to purchase Teradyne’s common stock at 100% of the fair market value on the grant date vest in equal annual installments over four years from the grant date and have a maximum term of seven years. Time-based restricted stock unit awards granted to employees vest in equal annual installments over four years. Restricted stock unit awards granted to non-employee directors vest in full, on the earlier of (a) the first anniversary of the grant date or (b) the date of the following year’s Annual Meeting of Shareholders. Teradyne expenses the cost of the restricted stock unit awards subject to time based vesting, which is determined to be the fair market value of the shares at the date of grant, ratably over the period during which the restrictions lapse. Teradyne grants performance-based restricted stock units (“PRSUs”) to its executive officers with a performance metric based on relative total shareholder return (“TSR”). For TSR grants issued in 2018, 2017, and 2016, Teradyne’s three-year TSR performance is measured against the New York Stock Exchange (“NYSE”) Composite Index. The final number of TSR PRSUs that vest will vary based upon the level of performance achieved from 200% to 0% of the target shares capped at four times the grant date value. The TSR PRSUs will vest upon the three-year anniversary of the grant date. The TSR PRSUs are valued using a Monte Carlo simulation model. The number of units expected to be earned, based upon the achievement of the TSR market condition, is factored into the grant date Monte Carlo valuation. Compensation expense is recognized on a straight-line basis over the shorter of the three-year service period or the period from the grant to the date described in the retirement provisions below. Compensation expense for employees meeting the retirement provisions prior to the grant date will be recognized in full on the date of the grant. Compensation expense is recognized regardless of the eventual number of units that are earned based upon the market condition, provided the executive officer remains an employee at the end of the three-year period. Compensation expense is reversed if at any time during the three-year service period the executive officer is no longer an employee, subject to the retirement and termination eligibility provisions noted below. In January 2018, 2017, and 2016, Teradyne granted PRSUs to its executive officers with a performance metric based on three-year cumulative non-GAAP profit before interest and tax (“PBIT”) as a percent of Teradyne’s revenue. Non-GAAP PBIT is a financial measure equal to GAAP income from operations less restructuring and other, net; amortization of acquired intangible assets; acquisition and divestiture related charges or credits; pension actuarial gains and losses; non-cash convertible debt interest expense; and other non-recurring gains and charges. The final number of PBIT PRSUs that vest will vary based upon the level of performance achieved from 200% to 0% of the target shares. The PBIT PRSUs will vest upon the three-year anniversary of the grant date. Compensation expense is recognized on a straight-line basis over the three-year service period. Compensation expense is recognized based on the number of units that are earned based upon the three-year Teradyne PBIT as a percent of Teradyne’s revenue, provided the executive officer remains an employee at the end of the three-year period subject to the retirement and termination eligibility provisions noted below. If a PRSU recipient’s employment ends prior to the determination of the performance percentage due to (1) permanent disability or death or (2) retirement or termination other than for cause, after attaining both at least age sixty and at least ten years of service, then all or a portion of the recipient’s PRSUs (based on the actual performance percentage achieved on the determination date) will vest on the date the performance percentage is determined. Except as set forth in the preceding sentence, no PRSUs will vest if the executive officer is no longer an employee at the end of the three-year period. During 2018, 2017, and 2016, Teradyne granted 0.1 million TSR PRSUs, with a grant date fair value of $54.85, $35.66 and $20.29, respectively. The fair value was estimated using the Monte Carlo simulation model with the following assumptions: 2018 2017 2016 Risk-free interest rate 2.2 % 1.5 % 1.0 % Teradyne volatility-historical 26.8 % 26.6 % 27.0 % NYSE Composite Index volatility-historical 12.4 % 13.4 % 13.1 % Dividend yield 0.8 % 1.0 % 1.2 % Expected volatility was based on the historical volatility of Teradyne’s stock and the NYSE Composite Index for the 2018, 2017 and 2016 grants, over the most recent three-year period. The risk-free interest rate was determined using the U.S. Treasury yield curve in effect at the time of grant. Dividend yield for 2018, 2017 and 2016 was based upon an estimated annual dividend amount of $0.36 per share for 2018, $0.28 per share for 2017 and $0.24 per share for 2016 divided by Teradyne’s stock price on the grant date of $47.70 for the 2018 grant, $28.56 for the 2017 grant, and $19.43 for the 2016 grant. During 2018, 2017, and 2016, Teradyne granted 0.1 million PBIT PRSUs with a grant date fair value of $46.62, $27.72 and $18.71, respectively. During 2018, 2017, and 2016, Teradyne granted 0.6 million, 0.8 million, and 1.2 million of service-based restricted stock unit awards to employees, respectively, at a weighted average grant date fair value of $45.92, $28.19, and $18.88, respectively. During 2018, 2017, and 2016, Teradyne granted 0.1 million of service-based restricted stock unit awards to non-employee During 2018, 2017, and 2016, Teradyne granted 0.1 million of service-based stock options to executive officers at a weighted average grant date fair value of $12.17, $7.13, and $5.30, respectively. The fair value of the stock options at grant date was estimated using the Black-Scholes option-pricing model with the following assumptions: 2018 2017 2016 Expected life (years) 5.0 5.0 5.0 Risk-free interest rate 2.4 % 2.0 % 1.4 % Volatility-historical 26.4 % 27.8 % 32.9 % Dividend yield 0.80 % 1.00 % 1.20 % Teradyne determined the stock option’s expected life based upon historical exercise data for executive officers, the age of executives and the terms of the stock option award. Volatility was determined using historical volatility for a period equal to the expected life. The interest rate was determined using the U.S. Treasury yield curve in effect at the time of grant. Dividend yield was based upon an estimated annual dividend amount of $0.36 per share for 2018, $0.28 per share for 2017, and $0.24 per share for 2016 divided by Teradyne’s stock price on the grant date of $47.70 for the 2018 grants, $28.56 for the 2017 grants, and $19.43 for the 2016 grants. Stock compensation plan activity for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 (in thousands) Restricted Stock Units: Non-vested 3,174 3,778 4,070 Awarded 790 939 1,471 Vested (1,382 ) (1,434 ) (1,530 ) Forfeited (128 ) (109 ) (233 ) Non-vested 2,454 3,174 3,778 Stock Options: Outstanding at January 1 531 926 1,121 Granted 69 111 130 Exercised (94 ) (501 ) (324 ) Expired — (5 ) (2 ) Outstanding at December 31 506 531 926 Vested and expected to vest at December 31 506 531 926 Exercisable at December 31 256 233 598 Total shares available for the years 2018, 2017, and 2016: 2018 2017 2016 (in thousands) Shares available: Available for grant at January 1 8,605 9,546 10,914 Options granted (69 ) (111 ) (130 ) Restricted stock units awarded (790 ) (939 ) (1,471 ) Restricted stock units forfeited 128 109 233 Available for grant at December 31 7,874 8,605 9,546 Weighted average restricted stock unit award date fair value information for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 Non-vested $ 21.71 $ 18.27 $ 17.66 Awarded 45.99 28.91 18.95 Vested 20.20 17.90 17.36 Forfeited 24.67 20.35 17.80 Non-vested $ 29.22 $ 21.71 $ 18.27 Restricted stock unit awards aggregate intrinsic value information at December 31 for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 (in thousands) Vested $ 63,688 $ 40,649 $ 30,008 Outstanding 77,015 132,875 95,952 Expected to vest 77,187 130,594 91,871 Restricted stock units weighted average remaining contractual terms (in years) information at December 31, for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 Outstanding 0.92 1.00 1.04 Expected to vest 0.91 0.99 1.03 Weighted average stock options exercise price information for the year ended December 31, 2018 is as follows: 2018 Outstanding at January 1 $ 13.92 Options granted 47.70 Options exercised 10.89 Outstanding at December 31 19.06 Exercisable at December 31 8.31 The total cash received from employees as a result of employee stock options exercises during the years ended December 31, 2018, 2017, and 2016, was $1.0 million, $6.8 million and $2.9 million, respectively. In connection with these exercises, the tax benefit realized by Teradyne for the years ended December 31, 2018, 2017, and 2016, was $0.4 million, $2.5 million, and $0.8 million, respectively. Stock option aggregate intrinsic value information for the years ended December 31, 2018, 2017, and 2016 is as follows: 2018 2017 2016 (in thousands) Exercised $ 2,960 $ 8,035 $ 3,729 Outstanding 7,359 14,831 12,468 Vested and expected to vest 7,359 14,831 12,468 Exercisable 5,905 9,076 10,217 Stock options weighted average remaining contractual terms (in years) information at December 31, for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 Outstanding 3.6 4.1 3.9 Vested and expected to vest 3.6 4.1 3.9 Exercisable 2.4 2.8 3.2 Significant option groups outstanding at December 31, 2018 and related weighted average price and remaining contractual life information follow: Options Outstanding Options Exercisable Range Of Exercise Prices Weighted- Average Remaining Contractual Life (Years) Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price (shares in thousands) $1.48 – $2.58 1.23 67 $ 1.83 67 $ 1.83 $2.67 – $3.28 2.20 103 2.69 103 2.69 $7.71 – $19.43 3.41 166 18.59 68 18.02 $28.56 – $47.70 5.62 170 36.30 18 28.56 506 $ 19.06 256 $ 8.31 As of December 31, 2018, total unrecognized expense related to non-vested Employee Stock Purchase Plan Under the ESPP, eligible employees may purchase shares of common stock through regular payroll deductions of up to 10% of their compensation, to a maximum of shares with a fair market value of $25,000 per calendar year, not to exceed 6,000 shares. Under the plan, the price paid for the common stock is equal to 85% of the stock price on the last business day of the six-month In July 2018, 0.3 million shares of common stock were issued to employees who participated in the plan during the first half of 2018 at the price of $32.36 per share. In January 2019, Teradyne issued 0.4 million shares of common stock to employees who participated in the plan during the second half of 2018 at the price of $26.67 per share. In July 2017, 0.3 million shares of common stock were issued to employees who participated in the plan during the first half of 2017 at the price of $25.53 per share. In January 2018, Teradyne issued 0.3 million shares of common stock to employees who participated in the plan during the second half of 2017 at the price of $35.59 per share. In July 2016, 0.5 million shares of common stock were issued to employees who participated in the plan during the first half of 2016 at the price of $16.74 per share. In January 2017, Teradyne issued 0.4 million shares of common stock to employees who participated in the plan during the second half of 2016 at the price of $21.59 per share. As of December 31, 2018, there were 2.5 million shares available for grant under the ESPP. The following table provides the effect to income from operations for recording stock-based compensation for the years ended December 31, 2018, 2017, and 2016: 2018 2017 2016 (in thousands) Cost of revenues $ 3,129 $ 3,212 $ 3,153 Engineering and development 9,181 9,370 9,458 Selling and administrative 21,267 21,515 18,139 Stock-based compensation 33,577 34,097 30,750 Income tax benefit (12,036 ) (10,462 ) (8,752 ) Total stock-based compensation expense after income taxes $ 21,541 $ 23,635 $ 21,998

Savings Plan

Savings Plan	12 Months Ended
	Dec. 31, 2018
Savings Plan	P. SAVINGS PLAN Teradyne sponsors a defined contribution employee retirement savings plan (“Savings Plan”) covering substantially all U.S. employees. Under the Savings Plan, employees may contribute up to 20 25 In addition, Teradyne established an unfunded U.S. Supplemental Savings Plan to provide savings benefits in excess of those allowed by the Employee Retirement Income Security Act of 1974 and the Internal Revenue Code. The provisions of this plan are the same as the Savings Plan. Teradyne also established defined contribution savings plans for its foreign employees. Under Teradyne’s savings plans, amounts charged to the statements of operations for the years ended December 31, 2018, 2017, and 2016 were $17.2 million, $15.3 million, and $14.5 million, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Taxes	Q. INCOME TAXES The components of income (loss) before income taxes and the provision (benefit) for income taxes as shown in the consolidated statements of operations were as follows: 2018 2017 2016 (in thousands) Income (loss) before income taxes: U.S. $ 189,691 $ 76,699 $ (341,018 ) Non-U.S. 278,110 447,713 285,958 $ 467,801 $ 524,412 $ (55,060 ) Provision (benefit) for income taxes: Current: U.S. Federal $ (59,122 ) $ 162,679 $ 7,750 Non-U.S. 45,083 64,313 41,579 State 1,721 2,623 1,968 (12,318 ) 229,615 51,297 Deferred: U.S. Federal 29,252 43,687 (51,482 ) Non-U.S. (1,243 ) (6,476 ) (9,240 ) State 331 (106 ) (2,214 ) 28,340 37,105 (62,936 ) Total provision (benefit) for income taxes: $ 16,022 $ 266,720 $ (11,639 ) Income tax expense for 2018 and 2017 totaled $ 16.0 266.7 11.6 3.4 50.9 21.1 On December 22, 2017, the U.S. enacted the Tax Cuts and Jobs Act of 2017 (the “Tax Reform Act”), making significant changes to the Internal Revenue Code. The Tax Reform Act has significant direct and indirect implications for accounting for income taxes under ASC 740, “Accounting for Income Taxes” some of which could not be calculated with precision until further clarification and guidance was made available from tax authorities, regulatory bodies or the FASB. In light of this uncertainty, on December 22, 2017 the SEC issued Staff Accounting Bulletin (“SAB”) No. 118, “Income Tax Accounting Implications of the Tax Cuts and Jobs Act,” to address uncertainty in the application of U.S. GAAP when the registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. In accordance with SAB 118, Teradyne recorded a provisional amount of $186.0 million of additional income tax expense in the fourth quarter of 2017 which represented Teradyne’s best estimate of the impact of the Tax Reform Act in accordance with Teradyne’s understanding of the Tax Reform Act and available guidance as of that date. The $186.0 million was primarily composed of expense of $161.0 million related to the one- time 49.5 one-time The Tax Reform Act also includes a new U.S. tax base erosion provision, the global intangible low-taxed income (“GILTI”) provision, which imposes a tax on foreign income in excess of a deemed return on tangible assets of foreign corporations. Teradyne has made an accounting policy election to account for GILTI as a component of tax expense in the period in which Teradyne is subject to the rules and therefore did not provide any deferred tax impacts of GILTI in its consolidated financial statements. The decrease in the effective tax rate from 2017 to 2018 was primarily attributable to the $186.0 million of income tax expense recorded in the fourth quarter of 2017 as a provisional estimate of the impact of the Tax Reform Act and the $51.7 million of income tax benefit recorded in the fourth quarter of 2018 resulting from a reduction in the estimate of the one-time non-taxable The increase in the effective tax rate from 2016 to 2017 was primarily attributable to the $186.0 million of income tax expense recorded in the fourth quarter of 2017 as a provisional estimate of the impact of the Tax Reform Act. The change in the effective rate from 2016 to 2017 was also impacted by the U.S. non-deductible non-taxable A reconciliation of the effective tax rate for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 U.S. statutory federal tax rate 21.0 % 35.0 % 35.0 % U.S. transition tax (10.5 ) 28.7 — U.S. foreign derived intangible income (1.8 ) — — Impact of rate change on deferred tax 0.3 6.9 — Uncertain tax positions 1.0 1.7 (2.6 ) Foreign taxes (2.0 ) (16.3 ) 78.0 Foreign tax credits (2.2 ) (2.2 ) 49.1 U.S. research and development credit (2.2 ) (1.6 ) 15.8 Equity compensation (1.2 ) (0.8 ) (2.7 ) State income taxes, net of federal tax benefit 0.1 (0.4 ) 2.3 Domestic production activities deduction — (0.3 ) 2.3 Goodwill impairment — — (162.1 ) U.S. alternative minimum tax credit — — 3.7 Inventory cost capitalization — — 1.8 Other, net 0.9 0.2 0.5 3.4 % 50.9 % 21.1 % Teradyne qualifies for a tax holiday in Singapore by fulfilling the requirements of an agreement with the Singapore Economic Development Board under which certain headcount and spending requirements must be met. The tax savings attributable to the Singapore tax holiday for the years ended December 31, 2018, 2017 and 2016 were $11.9 million or $0.06 per diluted share, $24.8 million or $0.12 per diluted share and $17.0 million or $0.08 per diluted share, respectively. The tax holiday is scheduled to expire on December 31, 2020. Significant components of Teradyne’s deferred tax assets (liabilities) as of December 31, 2018 and 2017 were as follows: 2018 2017 (in thousands) Deferred tax assets: Tax credits $ 69,091 $ 76,083 Accruals 23,449 27,508 Pension liabilities 20,826 22,602 Inventory valuations 18,514 17,793 Deferred revenue 9,130 9,016 Equity compensation 7,190 6,861 Vacation accrual 4,772 4,747 Net operating loss carryforwards 3,658 5,440 Marketable securities 962 — Other 685 713 Gross deferred tax assets 158,277 170,763 Less: valuation allowance (69,852 ) (63,919 ) Total deferred tax assets $ 88,425 $ 106,844 Deferred tax liabilities: Intangible assets $ (24,211 ) $ (16,120 ) Depreciation (14,028 ) (12,293 ) Marketable securities — (1,125 ) Total deferred tax liabilities $ (38,239 ) $ (29,538 ) Net deferred assets $ 50,186 $ 77,306 As of December 31, 2018 and 2017, Teradyne evaluated the likelihood that it would realize the deferred income taxes to offset future taxable income and concluded that it is more likely than not that a substantial majority of its deferred tax assets will be realized through consideration of both the positive and negative evidence. At December 31, 2018 and 2017, Teradyne maintained a valuation allowance for certain deferred tax assets of $69.9 million and $63.9 million, respectively, primarily related to state net operating losses and state tax credit carryforwards, due to the uncertainty regarding their realization. Adjustments could be required in the future if Teradyne estimates that the amount of deferred tax assets to be realized is more or less than the net amount recorded. At December 31, 2018, Teradyne had operating loss carryforwards that expire in the following years: State Operating Loss Carryforwards Foreign Operating Loss Carryforwards (in thousands) 2019 $ 258 $ — 2020 269 — 2021 2,977 — 2022 5,749 — 2023 6,241 — 2024-2028 4,672 — 2029-2033 22,724 44 Beyond 2033 5,305 72 Non-expiring — 4,389 Total $ 48,195 $ 4,505 Teradyne has approximately $98.4 million of tax credit carryforwards including federal business tax credits of approximately $ 0.9 Teradyne’s gross unrecognized tax benefits for the years ended December 31, 2018, 2017, and 2016 were as follows: 2018 2017 2016 (in thousands) Beginning balance, as of January 1 $ 36,263 $ 38,958 $ 36,792 Additions: Tax positions for current year 4,716 8,208 9,766 Tax positions for prior years 2,626 199 187 Reductions: Tax positions for prior years (153 ) (10,573 ) (1,960 ) Expiration of statutes (57 ) (325 ) (3,532 ) Settlements with tax authorities — (204 ) (2,295 ) Ending balance as of December 31 $ 43,395 $ 36,263 $ 38,958 Current year and prior year additions include assessment of potential transfer pricing issues worldwide, federal and state tax credits and incentives, capitalization rules, domestic production activities deductions and correlative effects of the transition tax charge. Of the $ 43.4 On February 4, 2019, the IRS issued a closing audit letter related to the U.S. Federal income tax return for the year ended December 31, 2015 indicating that there was no change to the reported tax. As a result of the completion of the 2015 audit, Teradyne anticipates recording a $ 33.8 33.8 5.9 27.9 2.0 Teradyne estimates that it is reasonably possible that the balance of unrecognized tax benefits as of December 31, 2018 may decrease an additional $ 0.2 Teradyne records all interest and penalties related to income taxes as a component of income tax expense. Accrued interest and penalties related to income tax items at December 31, 2018 and 2017 amounted to $0.3 million and $0.3 million, respectively. For the years ended December 31, 2018, 2017, and 2016, expense of $0.1 million, benefit of $0.1 million and benefit of $0.1 million, respectively, was recorded for interest and penalties related to income tax items. Teradyne is subject to U.S. federal income tax, as well as income tax in multiple state, local and foreign jurisdictions. As of December 31, 2018, all material state and local income tax matters have been concluded through 2013, all material federal income tax matters have been concluded through 2014 and all material foreign income tax matters have been concluded through 2012. However, in some jurisdictions, including the United States, operating losses and tax credits may be subject to adjustment until such time as they are utilized and the year of utilization is closed to adjustment. As of December 31, 2018, Teradyne is not permanently reinvested with respect to the unremitted earnings of non-U.S. subsidiaries to the extent that those earnings exceed local statutory and operational requirements. Remittance of those earnings is not expected to result in material income tax.

Operating Segment, Geographic a

Operating Segment, Geographic and Significant Customer Information	12 Months Ended
	Dec. 31, 2018
Operating Segment, Geographic and Significant Customer Information	R. OPERATING SEGMENT, GEOGRAPHIC AND SIGNIFICANT CUSTOMER INFORMATION Teradyne has four reportable segments (Semiconductor Test, System Test, Industrial Automation and Wireless Test). Each of the Semiconductor Test, System Test, and Wireless Test segments is also an individual operating segment. The Industrial Automation reportable segment consists of operating segments with discrete financial information, which have been combined into one reportable segment as they share similar economic characteristics, types of products, production processes, distribution channels, and currency risks. The Semiconductor Test segment includes operations related to the design, manufacturing and marketing of semiconductor test products and services. The System Test segment includes operations related to the design, manufacturing and marketing of products and services for defense/aerospace instrumentation test, storage test and circuit-board test. The Industrial Automation segment includes operations related to the design, manufacturing and marketing of collaborative robotic arms, autonomous mobile robots and advanced robotic control software. The Wireless Test segment includes operations related to the design, manufacturing and marketing of wireless test products and services. Teradyne evaluates performance based on several factors, of which the primary financial measure is business segment income (loss) before income taxes. The accounting policies of the business segments are the same as those described in Note B: “Accounting Policies.” Segment information for the years ended December 31, 2018, 2017, and 2016 is as follows: Semiconductor Test System Test Industrial Automation Wireless Test Corporate And Other Consolidated (in thousands) 2018 Revenues $ 1,492,417 $ 216,132 $ 261,452 $ 132,006 $ (1,205 ) $ 2,100,802 Income (loss) before taxes (1)(2) 397,645 48,857 7,670 29,052 (15,423 ) 467,801 Total assets (3) 669,452 88,098 607,502 77,570 1,263,984 2,706,606 Property additions 94,496 3,469 11,188 5,226 — 114,379 Depreciation and amortization expense 58,095 6,430 36,755 5,328 6,616 113,224 2017 Revenues $ 1,662,549 $ 192,135 $ 170,056 $ 111,866 $ — $ 2,136,606 Income (loss) before taxes (1)(2) 491,361 10,305 8,763 17,350 (3,368 ) 524,411 Total assets (3) 597,480 97,018 368,037 59,912 1,987,098 3,109,545 Property additions 87,920 5,976 7,044 4,435 — 105,375 Depreciation and amortization expense 58,901 6,646 25,711 5,392 11,425 108,075 2016 Revenues $ 1,368,169 $ 189,846 $ 99,031 $ 96,204 $ — $ 1,753,250 Income (loss) before taxes (1)(2) 311,939 28,916 (16,783 ) (371,409 ) (7,723 ) (55,060 ) Total assets (3) 557,546 110,361 317,635 62,366 1,714,585 2,762,493 Property additions 70,543 3,788 6,755 4,186 — 85,272 Depreciation and amortization expense 58,087 6,551 26,869 25,921 2,581 120,009 (1) Included in Corporate and Other are: contingent consideration adjustments, pension and postretirement plans actuarial gains (losses), severance charges, impairment of fixed assets and expenses related to the Japan earthquake, property insurance recovery, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations and acquisition related charges. (2) Included in income (loss) before taxes are charges and credits related to restructuring and other, and inventory charges. In 2016, loss before income taxes in Wireless Test also included charges related to goodwill and acquired intangible assets impairment. (3) Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets. Included in the Semiconductor Test segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Restructuring and other—employee severance $ 8,429 $ 1,779 $ 2,860 Cost of revenues—inventory charge 6,822 4,606 9,656 Restructuring and other—impairment of fixed assets — 1,124 — Included in the System Test segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Cost of revenues—inventory charge $ 1,175 $ 1,918 $ 630 Included in the Industrial Automation segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Restructuring and other—acquisition related expenses and compensation $ 1,163 $ — $ — Cost of revenues—inventory charge 680 — — Restructuring and other—employee severance — 1,414 585 Included in the Wireless Test segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Cost of revenues—inventory charge $ 2,565 $ 2,190 $ 7,207 Restructuring and other—lease impairment — 972 — Restructuring and other—employee severance — — 2,650 Goodwill impairment charge — — 254,946 Intangible assets impairment charge — — 83,339 Included in Corporate and Other are charges and credits in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Restructuring and other—MiR contingent consideration adjustment $ 17,666 $ — $ — Restructuring and other—Universal Robots contingent consideration adjustment (16,679 ) 7,820 15,346 Restructuring and other—acquisition related expenses 3,422 — — Restructuring and other 872 — — Restructuring and other—expense related to Japan earthquake and impairment of fixed assets — 755 5,051 Restructuring and other—property insurance recovery — (5,064 ) (5,051 ) Information as to Teradyne’s revenues by country is as follows: 2018 2017 2016 (in thousands) Revenues from customers (1): Taiwan $ 516,322 $ 687,031 $ 653,076 China 348,942 260,451 174,876 United States 282,869 252,516 221,948 Europe 223,207 163,715 117,671 Korea 163,224 206,819 147,882 Japan 158,281 169,093 135,978 Malaysia 122,797 124,048 103,472 Singapore 108,618 101,085 73,172 Philippines 77,996 105,850 54,705 Thailand 59,184 29,566 43,097 Rest of the World 39,362 36,432 27,373 $ 2,100,802 $ 2,136,606 $ 1,753,250 (1) Revenues attributable to a country are based on location of customer site. In 2018, no single customer accounted for more than 10% of total consolidated revenue. In 2017 and 2016, one customer of Teradyne’s Semiconductor Test segment accounted for 13 % and 12%, respectively, of total consolidated revenues. In 2016, a different customer of Teradyne’s Semiconductor Test segment accounted for 12% of total consolidated revenues. Teradyne estimates driven by a single OEM customer, combining direct sales to that customer with sales to the customer’s outsourced semiconductor assembly and test providers (“OSATs”), accounted for approximately 13%, 22%, and 26% of Teradyne’s consolidated revenues in 2018, 2017, and 2016, respectively. Long-lived assets by geographic area: United States Foreign(1) Total (in thousands) December 31, 2018 $ 209,368 $ 70,453 $ 279,821 December 31, 2017 $ 198,855 $ 69,592 $ 268,447 (1) As of December 31, 2018 and 2017, long-lived assets attributable to Singapore were $19.4 million and $23.6 million, respectively.

Stock Repurchase Program

Stock Repurchase Program	12 Months Ended
	Dec. 31, 2018
Stock Repurchase Program	S. STOCK REPURCHASE PROGRAM In January 2015, Teradyne’s Board of Directors authorized a stock repurchase program for up to $500 million of common stock. In 2016, Teradyne repurchased 6.8 In December 2016, Teradyne’s Board of Directors cancelled the January 2015 stock repurchase program and approved a new $500 million share repurchase authorization which commenced on January 1, 2017. The cumulative repurchases as of December 31, 2017 totaled 5.8 million shares of common stock for $200 million at an average price per share of $34.30. In January 2018, Teradyne’s Board of Directors cancelled the December 2016 stock repurchase program and authorized a new stock repurchase program for up to $1.5 billion of common stock. The cumulative repurchases as of December 31, 2018 totaled 21.6 million shares of common stock for $823.5 million at an average price per share of $38.06. Teradyne intends to repurchase $500 million in 2019.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events	T. SUBSEQUENT EVENTS In January 2019, Teradyne’s Board of Directors declared a quarterly cash dividend of $0.09 per share to be paid on March 22, 2019 to shareholders of record as of February 22, 2019. While declared a quarterly cash dividend and authorized a share repurchase program, it may reduce or eliminate the cash dividend or share repurchase program in the future. Future cash dividends and stock repurchases are subject to the discretion of ’s Board of Directors which will consider, among other things, ’s earnings, capital requirements and financial condition.

Supplementary Information

Supplementary Information	12 Months Ended
	Dec. 31, 2018
Supplementary Information	SUPPLEMENTARY INFORMATION (Unaudited) The following sets forth certain unaudited consolidated quarterly statements of operations data for each of Teradyne’s last eight quarters. In management’s opinion, this quarterly information reflects all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement for the periods presented. Such quarterly results are not necessarily indicative of future results of operations and should be read in conjunction with the audited consolidated financial statements of Teradyne and the notes thereto included elsewhere herein. 2018 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter (1) (2)(5) (3)(5) (4)(5) (in thousands, except per share amounts) Revenues: Products $ 403,925 $ 434,051 $ 470,994 $ 420,652 Services 83,542 92,878 95,854 98,906 Total revenues 487,467 526,929 566,848 519,558 Cost of revenues: Cost of products 180,958 180,777 195,339 170,064 Cost of services 36,677 38,818 37,816 39,959 Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below) 217,635 219,595 233,155 210,023 Gross profit 269,832 307,334 333,693 309,535 Operating expenses: Selling and administrative 90,505 99,410 100,202 100,552 Engineering and development 74,408 75,342 77,049 74,706 Acquired intangible assets amortization 7,698 9,793 11,142 10,558 Restructuring and other (313 ) 2,389 1,710 11,446 Total operating expenses 172,298 186,934 190,103 197,262 Income (loss) from operations 97,534 120,400 143,590 112,273 Non-operating Interest income (5,981 ) (5,427 ) (6,213 ) (9,083 ) Interest expense 6,890 5,639 5,557 13,182 Other (income) expense, net 805 176 3,405 (2,954 ) Income (loss) before income taxes 95,820 120,012 140,841 111,128 Income tax provision (benefit) 8,846 18,975 20,863 (32,662 ) Net income (loss) $ 86,974 $ 101,037 $ 119,978 $ 143,790 Net income (loss) per common share—basic $ 0.45 $ 0.53 $ 0.65 $ 0.80 Net income (loss) per common share—diluted $ 0.43 $ 0.52 $ 0.63 $ 0.79 Cash dividend declared per common share $ 0.09 $ 0.09 $ 0.09 $ 0.09 (1) 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. (2) 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. (3) 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. (4) 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. (5) Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy. 2017 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter (1) (2)(5) (3) (4)(5) (in thousands, except per share amounts) Revenues: Products $ 373,204 $ 610,356 $ 412,854 $ 388,282 Services 83,709 86,545 90,524 91,133 Total revenues 456,913 696,901 503,378 479,415 Cost of revenues: Cost of products 154,883 267,752 169,661 168,672 Cost of services 37,014 38,511 38,848 39,813 Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below) 191,897 306,263 208,509 208,485 Gross profit 265,016 390,638 294,869 270,930 Operating expenses: Selling and administrative 84,792 90,111 86,130 87,880 Engineering and development 75,978 82,270 76,986 72,070 Acquired intangible assets amortization 7,952 8,166 7,028 7,384 Restructuring and other 2,511 2,288 (4,407 ) 8,970 Total operating expenses 171,233 182,835 165,737 176,304 Income from operations 93,783 207,803 129,132 94,626 Non-operating Interest income (3,520 ) (3,292 ) (4,517 ) (6,476 ) Interest expense 5,402 5,509 5,372 5,380 Other (income) expense, net (115 ) (1,291 ) 840 (2,362 ) Income before income taxes 92,016 206,877 127,437 98,084 Income tax provision 6,795 31,901 24,017 204,007 Net income (loss) $ 85,221 $ 174,976 $ 103,420 $ (105,923 ) Net income (loss) per common share—basic $ 0.43 $ 0.88 $ 0.52 $ (0.54 ) Net income (loss) per common share—diluted $ 0.42 $ 0.87 $ 0.52 $ (0.54 ) Cash dividend declared per common share $ 0.07 $ 0.07 $ 0.07 $ 0.07 (1) Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges. (2) Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges. (3) Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges. (4) Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets. (5) Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
Valuation and Qualifying Accounts	TERADYNE, INC. SCHEDULE II—VALUATION AND QUALIFYING ACCOUNTS Column A Column B Column C Column D Column E Column F Description Balance at Beginning of Period Additions Charged to Cost and Expenses Other Deductions Balance at End of Period (in thousands) Valuation reserve deducted in the balance sheet from the asset to which it applies: Accounts receivable: 2018 Allowance for doubtful accounts $ 2,219 $ — $ 20 $ 566 $ 1,673 2017 Allowance for doubtful accounts $ 2,356 $ 4 $ — $ 141 $ 2,219 2016 Allowance for doubtful accounts $ 2,407 $ — $ — $ 51 $ 2,356 Column A Column B Column C Column D Column E Column F Description Balance at Beginning of Period Additions Charged to Cost and Expenses Other Deductions Balance at End of Period (in thousands) Valuation reserve deducted in the balance sheet from the asset to which it applies: Inventory: 2018 Inventory reserve $ 102,896 $ 11,242 $ 368 $ 13,727 $ 100,779 2017 Inventory reserve $ 116,016 $ 8,844 $ (126 ) $ 21,838 $ 102,896 2016 Inventory reserve $ 119,376 $ 17,493 $ 4,417 $ 25,270 $ 116,016 Column A Column B Column C Column D Column E Column F Description Balance at Beginning of Period Additions Charged to Cost and Expenses Other Deductions Balance at End of Period (in thousands) Valuation reserve deducted in the balance sheet from the asset to which it applies: Deferred taxes: 2018 Valuation allowance $ 63,919 $ 6,333 $ — $ 400 $ 69,852 2017 Valuation allowance $ 48,369 $ 15,571 $ — $ 21 $ 63,919 2016 Valuation allowance $ 43,039 $ 5,413 $ — $ 83 $ 48,369

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Preparation of Financial Statements and Use of Estimates	Preparation of Financial Statements and Use of Estimates The preparation of consolidated financial statements requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent liabilities. On an on-going
Revenue Recognition	Revenue Recognition Revenue from Contracts with Customers Teradyne adopted Accounting Standards Codification (“ASC”) 606, “ Revenue from Contracts with Customers” “Revenue Recognition,” In accordance with ASC 606, Teradyne recognizes revenues, when or as control is transferred to a customer. Teradyne’s determination of revenue is dependent upon a five step process outlined below. Step 1: Identify the contract with the customer Teradyne accounts for a contract with a customer when there is written approval, the contract is committed, the rights of the parties, including payment terms, are identified, the contract has commercial substance and consideration is probable of collection. Step 2: Identify the performance obligations in the contract Teradyne periodically enters into contracts with customers in which a customer may purchase a combination of goods and services, such as products with extended warranty obligations. Teradyne determines performance obligations by assessing whether the products or services are distinct from the other elements of the contract. In order to be distinct, the product or service must perform either on its own or with readily available resources and must be separate within the context of the contract. Step 3: Determine the transaction price Teradyne considers the amount stated on the face of the purchase order to be the transaction price. Teradyne does not have material variable consideration which could impact the stated purchase price agreed to by Teradyne and the customer. Step 4: Allocate the transaction price to the performance obligations in the contract Transaction price is allocated to each individual performance obligation based on the standalone selling price of that performance obligation. Teradyne uses standalone transactions when available to value each performance obligation. If standalone transactions are not available, Teradyne will estimate the standalone selling price through market assessments or cost plus a reasonable margin analysis. Any discounts from standalone selling price are spread proportionally to each performance obligation. Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation In order to determine the appropriate timing for revenue recognition, Teradyne first determines if the transaction meets any of three criteria for over time recognition. If the transaction meets the criteria for over time recognition, Teradyne recognizes revenue as the good or service is delivered. Teradyne uses input variables such as hours or months utilized or costs incurred to determine the amount of revenue to recognize in a given period. Input variables are used as they best align consumption with benefit to the customer. For transactions that do not meet the criteria for over time recognition, Teradyne will recognize revenue at a point in time based on an assessment of the five criteria for transfer of control. Teradyne has concluded that revenue should be recognized when shipped or delivered based on contractual terms. Typically, acceptance of Teradyne’s products and services is a formality as Teradyne delivers similar systems, instruments and robots to standard specifications. In cases where acceptance is not deemed a formality, Teradyne will defer revenue recognition until customer acceptance. Revenue recognized in accordance with ASC 606 was $2,088.8 million for the twelve months ended December 31, 2018. For the twelve months ended December 31, 2018, Teradyne also recognized $12.0 million in revenue on leases of Teradyne systems, which are accounted for outside of ASC 606. Disaggregation of Revenue The following table provides information about disaggregated revenue by primary geographical market, major product line and timing of revenue recognition. For the Year Ended December 31, 2018 Semiconductor Test System Test Industrial Automation Wireless Test Corporate and Other Consolidated System on a Chip Memory Defense/ Aerospace Storage Test Production Board Test Universal Robots Mobile Industrial Robots Energid (in thousands) Americas Point in time $ 43,398 $ 14,579 $ 59,246 $ 767 $ 9,082 $ 68,289 $ 7,326 $ 543 $ 17,730 $ (1,205 ) $ 219,755 Over time 35,100 2,774 24,577 — 3,091 649 — 997 1,436 — 68,624 Europe, Middle East and Africa Point in time 50,988 9,726 3,056 — 16,733 105,776 10,839 — 3,821 — 200,939 Over time 21,584 1,125 2,124 — 6,467 1,000 — 1,591 1,147 — 35,038 Asia Pacific Point in time 916,107 235,061 2,769 58,004 17,761 57,830 5,950 10 100,985 — 1,394,477 Over time 140,887 10,203 965 7,877 3,221 551 — 101 6,127 — 169,932 Lease revenue 10,885 — — — 392 — — — 760 — 12,037 Total $ 1,218,949 $ 273,468 $ 92,737 $ 66,648 $ 56,747 $ 234,095 $ 24,115 $ 3,242 $ 132,006 $ (1,205 ) $ 2,100,802 Performance Obligations Hardware Teradyne hardware consists primarily of semiconductor test systems and instruments, defense/aerospace test instrumentation and systems, storage test systems and instruments, circuit-board test and inspection systems and instruments, collaborative robots, autonomous mobile robots and wireless test systems. The hardware includes a standard 12-month warranty. This warranty is not considered a distinct performance obligation because it does not obligate Teradyne to provide a separate service to the customer and it cannot be purchased separately. Teradyne’s hardware is recognized at a point in time upon transfer of control to the customer. Extended Warranty Customers have the option to purchase an extended warranty, which extends the warranty period for systems and robots beyond the one-year Training and Applications Support Teradyne sells training and applications support to customers either in standalone transactions or included with system purchases. The training and support allow the customer to use Teradyne’s systems efficiently and effectively. Training and applications support included in system orders are valued based on their standalone selling price and all training and applications support is recognized over time as the customer receives and consumes the benefit associated with each. Both are recognized using an input method of hours consumed as this best depicts the transfer of services to the customer. Service Agreements Service agreements are recognized ratably over the period of agreement based on months completed. Post-Contract Customer Support (“PCS”) Teradyne provides support services for certain systems and robots outside of warranty. These services include telephone support, bug fixes, and when-and-if Teradyne does not allow customer returns or provide refunds to customers for any products or services. Contract Balances The following table provides information about contract liabilities. Teradyne does not have material contract assets on the balance sheet. December 31, 2018 January 1, 2018 (as adjusted) Increase (in thousands) Deferred revenue and customer advances $ 77,711 $ 76,638 $ 1,073 Long-term deferred revenue and customer advances 32,750 20,848 11,902 The amount of revenue recognized during the twelve months ended December 31 , 2018 that was previously included within the deferred revenue and customer advances balance was Practical Expedients Teradyne has adopted the practical expedients available within ASC 340 “Other Assets and Deferred Costs” Teradyne has adopted the practical expedient, which states an entity need not adjust the promised amount of consideration for the effects of a significant financing component if the entity expects, at contract inception, that the period between when the entity transfers a promised good or service to the customer and when the customer pays for that good or service will be one year or less. Teradyne does not have material payments associated with performance obligations outside this one-year Impacts The following tables summarize the impact of ASC 606 to Teradyne’s consolidated financial statements. Differences are the result of timing differences between the recognition of revenue under ASC 606 and ASC 605 primarily with respect to software transactions deferred due to lack of vendor specific objective evidence of price under ASC 605 and Teradyne’s assessment of acceptance under ASC 606. Under Legacy GAAP, Teradyne did not recognize revenue prior to acceptance if payment, title, or risk of loss was tied to acceptance. Under ASC 606, Teradyne recognizes revenue prior to receipt of acceptance if acceptance is deemed a formality. Condensed Consolidated Balance Sheet: December 31, 2018 As Reported Adjustments to Recognize under Legacy GAAP Legacy GAAP (in thousands, except per share amount) Assets Accounts receivable, less allowance for doubtful accounts $ 291,267 $ (37,348 ) $ 253,919 Inventories, net 153,541 10,759 164,300 Deferred tax assets 70,848 (3,874 ) 66,974 Liabilities Deferred revenue and customer advances $ 77,711 $ (4,118 ) $ 73,593 Income taxes payable 36,185 (4,495 ) 31,690 Long-term deferred revenue and customer advances 32,750 (10,303 ) 22,447 Shareholders’ equity Accumulated deficit $ (158,191 ) $ (11,547 ) $ (169,738 ) Condensed Consolidated Stateme nt of Operation: For the Year Ended December 31, 2018 As Reported Adjustments to Recognize under Legacy GAAP Legacy GAAP (in thousands, except per share amount) Total revenues $ 2,100,802 $ (39,184 ) $ 2,061,618 Total cost of revenues 880,408 (10,760 ) 869,648 Income tax provision 16,022 (4,197 ) 11,825 Net income 451,779 (24,227 ) 427,552 Net income per common share: Basic $ 2.41 $ (0.13 ) $ 2.28 Diluted $ 2.35 $ (0.13 ) $ 2.22 As of December 31, 2018 and 2017, deferred revenue and customer advances consisted of the following and are included in the short and long-term deferred revenue and customer advances: 2018 2017 (in thousands) Maintenance and training $ 58,362 $ 57,256 Extended warranty 27,422 24,438 Customer advances, undelivered elements and other 24,677 32,047 Total deferred revenue and customer advances $ 110,461 $ 113,741
Product Warranty	Product Warranty When Teradyne receives revenue for extended warranties, beyond one year, it is deferred and recognized on a straight-line basis over the contract period. Related costs are expensed as incurred. The balance below is included in short and long-term deferred revenue and customer advances: Amount (in thousands) Balance at December 31, 2015 $ 30,024 Deferral of new extended warranty revenue 19,909 Recognition of extended warranty deferred revenue (21,733 ) Balance at December 31, 2016 28,200 Deferral of new extended warranty revenue 20,513 Recognition of extended warranty deferred revenue (24,275 ) Balance at December 31, 2017 24,438 Deferral of new extended warranty revenue 23,753 Recognition of extended warranty deferred revenue (20,769 ) Balance at December 31, 2018 $ 27,422
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable are recorded at the invoiced amount and do not bear interest. The volatility of the industries that Teradyne serves can cause certain of its customers to experience shortages of cash flows, which can impact their ability to make required payments. Teradyne maintains allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. Estimated allowances for doubtful accounts are reviewed periodically taking into account the customer’s recent payment history, the customer’s current financial statements and other information regarding the customer’s credit worthiness. Account balances are written off against the allowance when it is determined the receivable will not be recovered. Teradyne sells certain trade accounts receivables on a non-recourse basis to third-party financial institutions pursuant to factoring agreements. Teradyne accounts for these transactions as sales of receivables and presents cash proceeds as a cash provided by operating activities in the consolidated statements of cash flows. Total trade accounts receivable sold under the factoring agreements were $52.2 million and $5.4 million during 2018 and 2017, respectively. Factoring fees for the sales of receivables were recorded in interest expense and were not material.
Inventories	Inventories Inventories are stated at the lower of cost (first-in, first-out
Investments	Investments Teradyne accounts for its investments in debt and equity securities in accordance with the provisions of ASC 320-10, Investments—Debt and Equity Securities 320-10 available-for-sale held-to-maturity • The length of time and the extent to which the market value has been less than cost; • The financial condition and near-term prospects of the issuer; and • The intent and ability to retain the investment in the issuer for a period of time sufficient to allow for any anticipated recovery in market value. Teradyne uses the market and income approach techniques to value its financial instruments and there were no changes in valuation techniques during the twelve months ended December 31, 2018 and 2017. As defined in ASC 820-10, “ Fair Value Measurements and Disclosures, Level 1: Quoted prices in active markets for identical assets as of the reporting date; Level 2: Inputs other than Level 1, that are observable either directly or indirectly as of the reporting date. For example, a common approach for valuing fixed income securities is the use of matrix pricing. Matrix pricing is a mathematical technique used to value securities by relying on the securities’ relationship to other benchmark quoted prices, and is considered a Level 2 input; or Level 3: Unobservable inputs that are not supported by market data. Unobservable inputs are developed based on the best information available, which might include ’s own data. In accordance with ASC 820-10, Teradyne measures its debt and equity investments at fair value. Teradyne’s debt investments are classified as Level 2, and equity investments are classified as Level 1. Acquisition-related contingent consideration is classified as Level 3. Teradyne determines the fair value of acquisition-related contingent consideration using a Monte Carlo simulation model. Assumptions utilized in the model include forecasted revenues, revenue volatility, earnings before interest and taxes, and discount rate.
Financial Assets and Financial Liabilities	Financial Assets and Financial Liabilities In January 2016 , the Financial Accounting Standards Board (“FASB”) issued ASU 2016 - 01 , “Financial Instruments—Overall (Subtopic 825 - 10) : Recognition and Measurement of Financial Assets and Financial Liabilities.” Teradyne adopted the new accounting guidance in the first quarter of 2018 using the modified retrospective approach. This guidance requires that changes in fair value of equity securities be accounted for directly in earnings. Previously, the changes in fair value were recorded in accumulated other comprehensive income on the balance sheet. Teradyne continues to record realized gains in interest income and realized losses in interest expense. The adoption of this new accounting guidance increased the January 1 , 2018 retained earnings balance by $3.1
Prepayments	Prepayments Prepayments consist of the following and are included in prepayments and other current assets on the balance sheet: 2018 2017 (in thousands) Contract manufacturer and supplier prepayments $ 131,642 $ 82,503 Prepaid taxes 9,646 5,039 Prepaid maintenance and other services 8,487 8,189 Other prepayments 12,744 12,386 Total prepayments $ 162,519 $ 108,117
Retirement and Postretirement Plans	Retirement and Postretirement Plans Teradyne recogn izes net ac tuarial gains and losses and the change in the fair value of the plan assets in its operating results in the year in which they occur or upon any interim remeasurement of the plans. Teradyne calculates the expected return on plan assets using the fair value of the plan assets. Actuarial gains and losses are generally measured annually as of December 31 and, accordingly, recorded during the fourth quarter of each year or upon any interim remeasurement of the plans.
Retirement Benefits	Retirement Benefits In March 2017 , the FA SB issu ed ASU 2017 - 07 , “ Compensation—Retirement Benefits (Topic 715) : Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost 2018 . This guidance requires the service cost component of net benefit costs to be reported in the same line item in the consolidated statement of operations as other employee compensation costs. The non-service components of net benefit costs such as interest cost, expected return on assets, amortization of prior service cost, and actuarial gains or losses, are required to be reported separately outside of income or loss from operations. Following the adoption of this guidance, Teradyne continues to record the service cost component in the same line item as other employee compensation costs and the non-service components of net benefit costs such as interest cost, expected return on assets, amortization of prior service cost, and actuarial gains or losses are reported within other (income) expense, net. In the twelve months ended December 31 , 2017 and 2016 , the retrospective adoption of this standard decreased income from operations by $ 5.0 million and $ 3.0 million, respectively, due to the removal of net actuarial pension gains and increased non-operating (income) expense by the same amount with no impact to net income.
Goodwill, Intangible and Long-Lived Assets	Goodwill, Intangible and Long-Lived Assets Teradyne accounts for go odwill an d intangible assets in accordance with ASC 350 - 10 , Intangibles-Goodwill and Other. 31 , on a reporting unit basis, or more frequently when events and circumstances occur indicating that the recorded goodwill may be impaired. In accordance with ASC 350 - 10 , more likely than not two-step more likely than not two-step In accordance with ASC 360 - 10 , Impairmen t or Disposal of Long-Lived Assets,
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cos t and depreciated over the estimated useful lives of the assets. Leasehold improvements and major renewals are capitalized and included in property, plant and equipment accounts while expenditures for maintenance and repairs and minor renewals are charged to expense. When assets are retired, the assets and related accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in the consolidated statements of operations. Teradyne provides for depreciation of its assets principally on the straight-line method with the cost of the assets being charged to expense over their useful lives as follows: Buildings 40 years Building improvements 5 to 10 years Leasehold improvements Lesser of lease term or 10 years Furniture and fixtures 10 years Test systems manufactured internally 6 years Machinery and equipment 3 to 5 years Software 3 to 5 years Test systems manufactured internally are used by Te radyne for customer evaluations and manufacturing and support of its customers. Teradyne depreciates the test systems manufactured internally over a six-year 31 , 2018 , 2017 , and 2016 was $3.8 million, $3.6 million, and $11.4 million, respectively.
Engineering and Development Costs	Engineering and Development Costs Teradyne’s products are highly technical in nature and require a larg e and continuing engineering and development effort. Software development costs incurred prior to the establishment of technological feasibility are charged to expense. Software development costs incurred subsequent to the establishment of technological feasibility are capitalized until the product is available for release to customers. To date, the period between achieving technological feasibility and general availability of the product has been short and software development costs eligible for capitalization have not been material. Engineering and development costs are expensed as incurred and consist primarily of salaries, contractor fees including non-recurring
Stock Compensation Plans and Employee Stock Purchase Plan	Stock Compensation Plans and Employee Stock Purchase Plan Stock-based compensation expense is based on the grant-date fair val ue e 718 - 10 , Compensation-Stock Compensation In March 2016 , the FASB issued ASU 2016 - 09 , “Compensation-Stoc k C 718) : Improvements to Employee Share-Based Payment Accounting.” 2017 . This ASU changes how Teradyne accounts for certain aspects of share-based payment awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statements of cash flows. Adoption of this ASU required recognition of a cumulative effect adjustment to reta million was recorded in the first quarter of 2017 as an increase to retained earnings and deferred tax assets. This ASU also required a change in how Teradyne recognizes the excess tax benefits or tax defic 2016 - 09 , paid-in 2016 - 09 , 2017 , these excess tax benefits or tax deficiencies are recognized as a discrete tax benefit or discrete tax expense to the current income tax provision in Teradyne’s consolidated statements of operations. ASU 2016 - 09 requires companies to adopt the amendment related to accounting for excess tax ben efit 2017 , Teradyne recognized a discrete tax benefit of $ 6.3 million related to net excess tax benefit. In addition, under ASU 2016 - 09 , as Upon adoption of ASU 2016 - 09 , or Under its stock compensation plans, Teradyne has granted stock options, restricted stock units and p erf Teradyne’s common stock through its Employee Stock Purchase Plan (“ESPP”).
Income Taxes	Income Taxes Deferred tax assets and liabilities are determined based on differences between financial re porti 740 , “Accounting for Income Taxes.”
Advertising Costs	Advertising Costs Teradyne expenses all advertising costs as incurred. Adve million, $9.1 million, and $6.4 million in 2018 , 2017 , and 2016 , respectively.
Translation of Non-U.S. Currencies	Translation of Non-U.S. The functional currency for all subsidiaries is the U.S. dollar, except for the Uni ver Net foreign exchange gains and losses resulting from remeasurement are included in other (incom e) e 31 , 2018 , 2017 , and 2016 , (gains) losses from the remeasurement of the monetary assets and liabilities denominated in foreign currencies were $(2.4) million, $2.9 million, and $(8.0) million, respectively. These amounts do not reflect the corresponding (gains) losses from foreign exchange con trac
Net Income (Loss) per Common Share	Net Income (Loss) per Common Share Basic net income (loss) per common share is calculated by dividing net income (loss) by the w With respect to its convertible debt issued in 2016 , Teradyne has determined that it has the abili ty a Teradyne is accounting for the conversion spread using the treasury stock method.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) includes net income, unrealized pension and postretirement prior service costs and benefits, unrealized gains and losses on investments in debt marketable securities and foreign currency translation adjustment. Prior to 2018, comprehensive income (loss) included unrealized gains and losses on investments in equity marketable securities.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition	The following table provides information about disaggregated revenue by primary geographical market, major product line and timing of revenue recognition. For the Year Ended December 31, 2018 Semiconductor Test System Test Industrial Automation Wireless Test Corporate and Other Consolidated System on a Chip Memory Defense/ Aerospace Storage Test Production Board Test Universal Robots Mobile Industrial Robots Energid (in thousands) Americas Point in time $ 43,398 $ 14,579 $ 59,246 $ 767 $ 9,082 $ 68,289 $ 7,326 $ 543 $ 17,730 $ (1,205 ) $ 219,755 Over time 35,100 2,774 24,577 — 3,091 649 — 997 1,436 — 68,624 Europe, Middle East and Africa Point in time 50,988 9,726 3,056 — 16,733 105,776 10,839 — 3,821 — 200,939 Over time 21,584 1,125 2,124 — 6,467 1,000 — 1,591 1,147 — 35,038 Asia Pacific Point in time 916,107 235,061 2,769 58,004 17,761 57,830 5,950 10 100,985 — 1,394,477 Over time 140,887 10,203 965 7,877 3,221 551 — 101 6,127 — 169,932 Lease revenue 10,885 — — — 392 — — — 760 — 12,037 Total $ 1,218,949 $ 273,468 $ 92,737 $ 66,648 $ 56,747 $ 234,095 $ 24,115 $ 3,242 $ 132,006 $ (1,205 ) $ 2,100,802
Information about Contract Liabilities	The following table provides information about contract liabilities. Teradyne does not have material contract assets on the balance sheet. December 31, 2018 January 1, 2018 (as adjusted) Increase (in thousands) Deferred revenue and customer advances $ 77,711 $ 76,638 $ 1,073 Long-term deferred revenue and customer advances 32,750 20,848 11,902
Deferred Revenue and Customer Advances	As of December 31, 2018 and 2017, deferred revenue and customer advances consisted of the following and are included in the short and long-term deferred revenue and customer advances: 2018 2017 (in thousands) Maintenance and training $ 58,362 $ 57,256 Extended warranty 27,422 24,438 Customer advances, undelivered elements and other 24,677 32,047 Total deferred revenue and customer advances $ 110,461 $ 113,741
Other Accrued Liabilities	The balance below is included in other accrued liabilities: Amount (in thousands) Balance at December 31, 2015 $ 6,925 Accruals for warranties issued during the period 14,291 Accruals related to pre-existing (1,354 ) Settlements made during the period (12,659 ) Balance at December 31, 2016 7,203 Accruals for warranties issued during the period 14,223 Accruals related to pre-existing (379 ) Settlements made during the period (12,847 ) Balance at December 31, 2017 8,200 Acquisition 41 Accruals for warranties issued during the period 13,045 Accruals related to pre-existing 921 Settlements made during the period (14,298 ) Balance at December 31, 2018 $ 7,909
Extended Product Warranty of Short and Long-Term Deferred Revenue and Customer Advances	The balance below is included in short and long-term deferred revenue and customer advances: Amount (in thousands) Balance at December 31, 2015 $ 30,024 Deferral of new extended warranty revenue 19,909 Recognition of extended warranty deferred revenue (21,733 ) Balance at December 31, 2016 28,200 Deferral of new extended warranty revenue 20,513 Recognition of extended warranty deferred revenue (24,275 ) Balance at December 31, 2017 24,438 Deferral of new extended warranty revenue 23,753 Recognition of extended warranty deferred revenue (20,769 ) Balance at December 31, 2018 $ 27,422
Schedule of Prepayments and Other Current Assets	Prepayments consist of the following and are included in prepayments and other current assets on the balance sheet: 2018 2017 (in thousands) Contract manufacturer and supplier prepayments $ 131,642 $ 82,503 Prepaid taxes 9,646 5,039 Prepaid maintenance and other services 8,487 8,189 Other prepayments 12,744 12,386 Total prepayments $ 162,519 $ 108,117
Useful Lives of Assets	Teradyne provides for depreciation of its assets principally on the straight-line method with the cost of the assets being charged to expense over their useful lives as follows: Buildings 40 years Building improvements 5 to 10 years Leasehold improvements Lesser of lease term or 10 years Furniture and fixtures 10 years Test systems manufactured internally 6 years Machinery and equipment 3 to 5 years Software 3 to 5 years
ASU 2014-09
Summarize Impact of ASC 606 to Consolidated Financial Statements	The following tables summarize the impact of ASC 606 to Teradyne’s consolidated financial statements. Differences are the result of timing differences between the recognition of revenue under ASC 606 and ASC 605 primarily with respect to software transactions deferred due to lack of vendor specific objective evidence of price under ASC 605 and Teradyne’s assessment of acceptance under ASC 606. Under Legacy GAAP, Teradyne did not recognize revenue prior to acceptance if payment, title, or risk of loss was tied to acceptance. Under ASC 606, Teradyne recognizes revenue prior to receipt of acceptance if acceptance is deemed a formality. Condensed Consolidated Balance Sheet: December 31, 2018 As Reported Adjustments to Recognize under Legacy GAAP Legacy GAAP (in thousands, except per share amount) Assets Accounts receivable, less allowance for doubtful accounts $ 291,267 $ (37,348 ) $ 253,919 Inventories, net 153,541 10,759 164,300 Deferred tax assets 70,848 (3,874 ) 66,974 Liabilities Deferred revenue and customer advances $ 77,711 $ (4,118 ) $ 73,593 Income taxes payable 36,185 (4,495 ) 31,690 Long-term deferred revenue and customer advances 32,750 (10,303 ) 22,447 Shareholders’ equity Accumulated deficit $ (158,191 ) $ (11,547 ) $ (169,738 ) Condensed Consolidated Stateme nt of Operation: For the Year Ended December 31, 2018 As Reported Adjustments to Recognize under Legacy GAAP Legacy GAAP (in thousands, except per share amount) Total revenues $ 2,100,802 $ (39,184 ) $ 2,061,618 Total cost of revenues 880,408 (10,760 ) 869,648 Income tax provision 16,022 (4,197 ) 11,825 Net income 451,779 (24,227 ) 427,552 Net income per common share: Basic $ 2.41 $ (0.13 ) $ 2.28 Diluted $ 2.35 $ (0.13 ) $ 2.22

Acquisitions (Tables)

Acquisitions (Tables) - Mobile Industrial Robots (MiR)	12 Months Ended
	Dec. 31, 2018
Final Allocation of Purchase Price	The following table represents the final allocation of the purchase price: Purchase Price Allocation (in thousands) Goodwill $ 135,976 Intangible assets 80,670 Tangible assets acquired and liabilities assumed: Current assets 6,039 Non-current assets 1,336 Accounts payable and current liabilities (7,336 ) Long-term deferred tax liabilities (18,007 ) Other long-term liabilities (900 ) Total purchase price $ 197,778
Components of Intangible Assets and Their Estimated Useful Lives at Acquisition Date	Components of these intangible assets and their estimated useful lives at the acquisition date are as follows: Fair Value Estimated Useful Life (in thousands) (in years) Developed technology $ 58,900 7.0 Trademarks and tradenames 13,240 11.0 Customer relationships 8,500 2.5 Backlog 30 0.2 Total intangible assets $ 80,670 7.2
Pro Forma Results Under Acquisitions	The unaudited pro forma results are not necessarily indicative of what actually would have occurred had the acquisition been in effect for the periods presented: For the Year Ended December 31, 2018 December 31, 2017 (in thousands, except per share amounts) Revenues $ 2,107,600 $ 2,148,320 Net income $ 450,559 $ 243,399 Net income per common share: Basic $ 2.40 $ 1.23 Diluted $ 2.34 $ 1.21

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2018
Composition of Inventories, Net	Inventories, net consisted of the following at December 31, 2018 and 2017: 2018 2017 (in thousands) Raw material $ 89,365 $ 62,668 Work-in-process 31,014 19,464 Finished goods 33,162 25,393 $ 153,541 $ 107,525

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant and Equipment, Net	Property, plant and equipment, net consisted of the following at December 31, 2018 and 2017: 2018 2017 (in thousands) Land $ 16,561 $ 16,561 Buildings 105,935 98,369 Machinery and equipment 689,770 647,961 Furniture and fixtures, and software 90,384 88,539 Leasehold improvements 52,536 49,540 Construction in progress 6,276 13,522 961,462 914,492 Less: accumulated depreciation 681,641 646,045 $ 279,821 $ 268,447

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following table sets forth by fair value hierarchy Teradyne’s financial assets and liabilities that were measured at fair value on a recurring basis as of December 31, 2018 and 2017: December 31, 2018 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 312,512 $ — $ — $ 312,512 Cash equivalents 253,525 360,715 — 614,240 Available for sale securities: U.S. Treasury securities — 109,721 — 109,721 Commercial paper — 86,117 — 86,117 Corporate debt securities — 40,020 — 40,020 U.S. government agency securities — 9,611 — 9,611 Certificates of deposit and time deposits — 7,604 — 7,604 Debt mutual funds 3,187 — — 3,187 Non-U.S. — 376 — 376 Equity securities: Mutual funds 21,191 — — 21,191 590,415 614,164 — 1,204,579 Derivative assets — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Contingent consideration $ — $ — $ 70,543 $ 70,543 Derivative liabilities — 514 — 514 Total $ — $ 514 $ 70,543 $ 71,057 Reported as follows: Level 1 Level 2 Level 3 Total (in thousands) Assets Cash and cash equivalents $ 566,037 $ 360,715 $ — $ 926,752 Marketable securities — 190,096 — 190,096 Long-term marketable securities 24,378 63,353 — 87,731 Prepayments — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Other current liabilities $ — $ 514 $ — $ 514 Contingent consideration — — 34,865 34,865 Long-term contingent consideration — — 35,678 35,678 Total $ — $ 514 $ 70,543 $ 71,057 December 31, 2017 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 197,955 $ — $ — $ 197,955 Cash equivalents 206,335 25,553 — 231,888 Available for sale securities: U.S. Treasury securities — 855,795 — 855,795 Commercial paper — 282,840 — 282,840 Certificates of deposit and time deposits — 167,342 — 167,342 Corporate debt securities — 133,186 — 133,186 Equity and debt mutual funds 23,430 — — 23,430 U.S. government agency securities — 10,726 — 10,726 Non-U.S. — 586 — 586 427,720 1,476,028 — 1,903,748 Derivative assets — 389 — 389 Total $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Contingent consideration $ — $ — $ 45,102 $ 45,102 Derivative liabilities — 446 — 446 Total $ — $ 446 $ 45,102 $ 45,548 Reported as follows: Level 1 Level 2 Level 3 Total (in thousands) Assets Cash and cash equivalents $ 404,290 $ 25,553 $ — $ 429,843 Marketable securities — 1,347,979 — 1,347,979 Long-term marketable securities 23,430 102,496 — 125,926 Prepayments — 389 — 389 $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Other current liabilities $ — $ 446 $ — $ 446 Contingent consideration — — 24,497 24,497 Long-term contingent consideration — — 20,605 20,605 $ — $ 446 $ 45,102 $ 45,548
Schedule of Changes in Fair Value of Level 3 Contingent Consideration	Changes in the fair value of Level 3 contingent consideration for the years ended December 31, 2018 and 2017 were as follows: Contingent Consideration (in thousands) Balance at December 31, 2016 $ 38,332 Payments (1) (1,050 ) Fair value adjustment (2) 7,820 Balance at December 31, 2017 45,102 Acquisition of MiR 52,547 Foreign currency impact (3,540 ) Payments (3) (24,553 ) Fair value adjustment (4) 987 Balance at December 31, 2018 $ 70,543 (1) During the year ended December 31, 2017, Teradyne paid $1.1 million of contingent consideration for the earn-out in connection with the acquisition of Avionics Interface Technologies, LLC (“AIT”). (2) During the year ended December 31, 2017, the fair value of contingent consideration for the earn-out (3) During the year ended December 31, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out (4) During the year ended December 31, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of MiR was increased by $ 17.7 16.7
Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument	The following table provides quantitative information associated with the fair value measurement of Teradyne’s Level 3 financial instrument: Liability December 31, 2018 Fair Value Valuation Technique Unobservable Inputs Weighted Average (in thousands) Contingent consideration (MiR) $ 66,672 (1) Monte Carlo simulation Revenue volatility 18.0 % Discount rate 1.1 % Contingent consideration (Universal Robots) $ 3,871 (1) (1) Contingent consideration related to MiR and acquisitions of $31.0 million and $3.9 million, respectively, is expected to be paid in March 2019.
Schedule of Carrying Amounts and Fair Values of Financial Instruments	The carrying amounts and fair values of Teradyne’s financial instruments at December 31, 2018 and 2017 were as follows: December 31, 2018 December 31, 2017 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 926,752 $ 926,752 $ 429,843 $ 429,843 Marketable securities 277,827 277,827 1,473,905 1,473,905 Derivative assets 79 79 389 389 Liabilities Contingent consideration 70,543 70,543 45,102 45,102 Derivative liabilities 514 514 446 446 Convertible debt (1) 379,981 547,113 365,987 659,525 (1) The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note which includes the equity conversion features.
Schedule of Available-for-Sale Marketable Securities	The following tables summarize the composition of available-for-sale marketable securities at December 31, 2018 and 2017: December 31, 2018 Available-for-Sale Fair Market Cost Unrealized Gain Unrealized (Loss) Fair Market Value Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 110,969 $ 112 $ (1,360 ) $ 109,721 $ 75,040 Commercial paper 86,130 13 (26 ) 86,117 85,094 Corporate debt securities 41,133 432 (1,545 ) 40,020 24,767 U.S. government agency securities 9,646 1 (36 ) 9,611 7,077 Certificates of deposit and time deposits 7,604 — — 7,604 — Debt mutual funds 3,153 34 — 3,187 — Non-U.S. 376 — — 376 — $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 190,100 $ 88 $ (92 ) $ 190,096 $ 140,262 Long-term marketable securities 68,911 504 (2,875 ) 66,540 51,716 $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 December 31, 2017 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 858,258 $ 72 $ (2,535 ) $ 855,795 $ 850,163 Commercial paper 283,009 18 (187 ) 282,840 258,933 Certificates of deposit and time deposits 167,523 6 (187 ) 167,342 138,340 Corporate debt securities 131,179 2,380 (373 ) 133,186 91,010 Equity and debt mutual funds 19,403 4,102 (75 ) 23,430 1,723 U.S. government agency securities 10,775 — (49 ) 10,726 10,727 Non-U.S. 582 4 — 586 — $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 1,349,970 $ 38 $ (2,029 ) $ 1,347,979 $ 1,288,844 Long-term marketable securities 120,759 6,544 (1,377 ) 125,926 62,052 $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896
Contractual Maturities of Investments Held	The contractual maturities of investments in available-for-sale marketable securities held at December 31, 2018 were as follows: Cost Fair Value (in thousands) Due within one year $ 190,100 $ 190,096 Due after 1 year through 5 years 9,199 9,144 Due after 5 years through 10 years 14,081 13,405 Due after 10 years 42,478 40,804 Total $ 255,858 $ 253,449
Schedule of Notional Amount of Derivatives	At December 31, 2018 and 2017, Teradyne had the following contracts to buy and sell non-U.S. non-U.S. December 31, 2018 December 31, 2017 Buy Position Sell Position Net Total Buy Position Sell Position Net Total (in millions) Japanese Yen $ (35.0 ) $ — $ (35.0 ) $ (35.7 ) $ — $ (35.7 ) Taiwan Dollar (11.2 ) — (11.2 ) (9.9 ) — (9.9 ) Korean Won (9.6 ) — (9.6 ) (8.9 ) — (8.9 ) British Pound Sterling (1.4 ) — (1.4 ) (1.4 ) — (1.4 ) Euro — 82.2 82.2 — 27.4 27.4 Singapore Dollar — 15.7 15.7 — 33.5 33.5 Philippine Peso — 5.2 5.2 — — — Chinese Yuan — 2.8 2.8 — — — Total $ (57.2 ) $ 105.9 $ 48.7 $ (55.9 ) $ 60.9 $ 5.0
Schedule of Derivative Instruments in Statement of Financial Position at Fair Value	The following table summarizes the fair value of derivative instruments as of December 31, 2018 and 2017: Balance Sheet Location December 31, 2018 December 31, 2017 (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Prepayments $ 79 $ 389 Foreign exchange contracts Other current liabilities (514 ) (446 ) Total derivatives $ (435 ) $ (57 )
Schedule of Effect of Derivative Instruments on Statement of Operations Recognized	The following table summarizes the effect of derivative instruments in the statements of operations recognized for the years ended December 31, 2018, 2017, and 2016. Location of (Gains) Losses Recognized in Statement of Operations 2018 2017 2016 (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Other (income) expense, net $ 7,257 $ (1,133 ) $ 8,671 (1) The table does not reflect the corresponding gains and losses from the remeasurement of the monetary assets and liabilities denominated in foreign currencies. (2) For the years ended December 31, 2018 and 2016, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $2.4 (3) For the year ended December 31, 2017, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $2.9 million.

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Components of Convertible Senior Notes	The below tables represents the key components of Teradyne’s convertible senior notes: December 31, 2018 December 31, 2017 (in thousands) Debt principal $ 460,000 $ 460,000 Unamortized discount 80,019 94,013 Net carrying amount of convertible debt $ 379,981 $ 365,987 For the year ended December 31, 2018 December 31, 2017 (in thousands) Contractual interest expense on the coupon $ 5,750 $ 5,734 Amortization of the discount component and debt issue fees recognized as interest expense 13,995 13,318 Total interest expense on the convertible debt $ 19,745 $ 19,052

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive (Loss) Income (Tables)	12 Months Ended
	Dec. 31, 2018
Changes in Accumulated Other Comprehensive (Loss) Income	Changes in accumulated other comprehensive (loss) income, which is presented net of tax, consist of the following: Foreign Currency Translation Adjustment Unrealized Gains on Marketable Securities Retirement Plans Prior Service Credit Total (in thousands) Balance at December 31, 2016, net of tax of $0, $209, $(778) $ (21,921 ) $ (60 ) $ 1,767 $ (20,214 ) Other comprehensive income before reclassifications, net of tax of $0, $1,903, $0 37,840 1,863 — 39,703 Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(297), $(154) — (441 ) (272 ) (713 ) Net current period other comprehensive income, net of tax of $0, $1,606, $(154) 37,840 1,422 (272 ) 38,990 Balance at December 31, 2017, net of tax of $0, $1,815, $(932) 15,919 1,362 1,495 18,776 Other comprehensive loss before reclassifications, net of tax of $0, $(722), $0 (28,442 ) (2,110 ) — (30,552 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(21), $(71) — 1,337 (245 ) 1,092 Net current period other comprehensive loss, net of tax of $0, $(743), $(71) (28,442 ) (773 ) (245 ) (29,460 ) Reclassification of tax effects resulting from the Tax Reform Act, net of tax of $0, $(691), $(78), respectively (a) — 691 78 769 Reclassification of unrealized gains on equity securities, net of tax of $0, $(902), $0, respectively, (b) — (3,125 ) — (3,125 ) Balance at December 31, 2018, net of tax of $0, $(521), $(1,081) $ (12,523 ) $ (1,845 ) $ 1,328 $ (13,040 ) (a) In the year ended December 31, 2018, Teradyne early adopted ASU 2018-02, “Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” As a result, the stranded tax effects resulting from the Tax Reform Act enacted in December 2017 were reclassified from accumulated other comprehensive income to retained earnings. (b) In the year ended December 31, 2018, Teradyne adopted ASU 2016-01, “ Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities .” See Note B: “Accounting Policies.”
Reclassifications Out of Accumulated Other Comprehensive Income to Statements of Operations	Reclassifications out of accumulated other comprehensive income to the statements of operations for the years ended December 31, 2018, 2017, and 2016 were as follows: Details about Accumulated Components For the year ended Affected Line Item in the Statements of Operations December 31, 2018 December 31, 2017 December 31, 2016 (in thousands) Available-for-sale marketable securities Unrealized (losses) gains, net of tax of $21, $297, $255 $ (1,337 ) $ 441 $ 683 Interest income (expense) Defined benefit pension and postretirement plans: Amortization of prior service benefit, net of tax of $71, $154, $190 245 272 321 (a) Total reclassifications, net of tax of $92, $451, $445 $ (1,092 ) $ 713 $ 1,004 Net income (a) The amortization of prior service credit is included in the computation of net periodic pension cost and postretirement benefit; see Note N: “Retirement Plans.”

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Changes in Carrying Amount of Goodwill by Segment	The changes in the carrying amount of goodwill by reportable segments for the years ended December 31, 2018 and 2017 are as follows: Industrial Automation System Test Wireless Test Semiconductor Test Total (in thousands) Balance at December 31, 2016: Goodwill $ 204,851 $ 158,699 $ 361,819 $ 260,540 $ 985,909 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 204,851 10,516 7,976 — 223,343 Foreign currency translation adjustment 28,668 — — — 28,668 Balance at December 31, 2017: Goodwill 233,519 158,699 361,819 260,540 1,014,577 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 233,519 10,516 7,976 — 252,011 MiR acquisition 135,976 — — — 135,976 Energid acquisition 14,394 — — — 14,394 Foreign currency translation adjustment (20,531 ) — — — (20,531 ) Balance at December 31, 2018: Goodwill 363,358 158,699 361,819 260,540 1,144,416 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) $ 363,358 $ 10,516 $ 7,976 $ — $ 381,850
Schedule of Amortizable Intangible Assets	Amortizable intangible assets consist of the following and are included in intangible assets, net on the balance sheets: December 31, 2018 Gross Carryin Amount (1)(2) Accumulated Amortization (2) Foreign Currency Translation Adjustment Net Carrying Amount (in thousan ds) Developed technology $ 336,308 $ (252,080 ) $ (4,079 ) $ 80,149 Customer relationships 97,153 (83,448 ) (340 ) 13,365 Tradenames and trademarks 64,420 (31,653 ) (799 ) 31,968 Non-compete agreement 320 (320 ) — — Backlog 30 (30 ) — — Total intangible assets $ 498,231 $ (367,531 ) $ (5,218 ) $ 125,482 December 31, 2017 Gross Carrying Amount Accumulated Amortization Foreign Currency Translation Adjustment Net Carrying Amount (in thousands) Developed technology $ 270,877 $ (226,190 ) $ 1,618 $ 46,305 Customer relationships 92,741 (83,585 ) 171 9,327 Tradenames and trademarks 50,100 (27,120 ) 416 23,396 Non-compete agreement 320 (260 ) — 60 Total intangible assets $ 414,038 $ (337,155 ) $ 2,205 $ 79,088
Wireless Test
Schedule of Estimated Intangible Assets Amortization Expense	Estimated intangible assets amortization expense for each of the five succeeding fiscal years is as follows: Year Amortization Expense (in thousands) 2019 $ 38,496 2020 24,186 2021 13,945 2022 13,052 2023 12,785 Thereafter 23,018

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Non-Cancelable Operating Lease Commitments	The following table reflects Teradyne’s non-cancelable Non-cancelable Lease Commitments (in thousands) 2019 $ 19,570 2020 18,293 2021 13,578 2022 9,693 2023 5,449 Beyond 2024 9,472 Total $ 76,055

Net Income (Loss) per Common _2

Net Income (Loss) per Common Share (Tables)	12 Months Ended
	Dec. 31, 2018
Computation of Basic and Diluted Net Income (Loss) Per Common Share	The following table sets forth the computation of basic and diluted net income (loss) per common share: 2018 2017 2016 (in thousands, except per share amounts) Net income (loss) for basic and diluted net income per share $ 451,779 $ 257,692 $ (43,421 ) Weighted average common shares-basic 187,672 198,069 202,578 Effect of dilutive potential common shares: Incremental shares from assumed conversion of convertible notes (1) 2,749 1,298 — Convertible note hedge warrant shares (2) 485 112 — Restricted stock units 1,385 1,800 — Stock options 278 335 0 Employee stock purchase rights 36 27 0 Dilutive potential common shares 4,933 3,572 — Weighted average common shares-diluted 192,605 201,641 202,578 Net income (loss) per common share-basic $ 2.41 $ 1.30 $ (0.21 ) Net income (loss) per common share-diluted $ 2.35 $ 1.28 $ (0.21 ) (1) Incremental shares from the assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.70, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period. (2) Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.78, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period.

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Defined Benefit Pension Plans
Defined Benefit Pension and Postretirement Benefit Plan Assets and Obligations	The December 31 balances of these defined benefit pension plans assets and obligations are shown below: 2018 2017 United States Foreign United States Foreign (in thousands) Assets and Obligations Change in benefit obligation: Projected benefit obligation: Beginning of year $ 363,026 $ 39,353 $ 353,616 $ 60,738 Service cost 2,196 786 2,239 818 Interest cost 8,940 687 13,151 852 Actuarial (gain) loss (30,136 ) 773 12,702 262 Benefits paid (14,793 ) (741 ) (18,682 ) (994 ) Retiree annuity purchase (151,341 ) — — — Liability loss due to settlement 345 — — — Settlements — — — (28,560 ) Admin expenses paid — — — (40 ) Non-U.S. — (1,712 ) — 6,277 End of year 178,237 39,146 363,026 39,353 Change in plan assets: Fair value of plan assets: Beginning of year 324,506 1,307 307,304 27,571 Company contributions 2,587 822 4,462 883 Actual return on plan assets (16,658 ) 50 31,422 737 Benefits paid (14,793 ) (741 ) (18,682 ) (994 ) Retiree annuity purchase (151,341 ) — — — Settlements — — — (28,560 ) Admin expenses paid — — — (40 ) Non-U.S. — (38 ) — 1,710 End of year 144,301 1,400 324,506 1,307 Funded status $ (33,936 ) $ (37,746 ) $ (38,520 ) $ (38,046 )
Amounts Recorded within Statement of Financial Position	The following table provides amounts recorded within the account line items of the statements of financial position as of December 31: 2018 2017 United States Foreign United States Foreign (in thousands) Retirement plans assets $ 16,883 $ — $ 17,491 $ — Accrued employees’ compensation and withholdings (2,676 ) (852 ) (2,524 ) (863 ) Retirement plans liabilities (48,143 ) (36,894 ) (53,487 ) (37,183 ) Funded status $ (33,936 ) $ (37,746 ) $ (38,520 ) $ (38,046 )
Amounts Recognized in Accumulated Other Comprehensive Income	The following table provides amounts recognized in accumulated other comprehensive income as of December 31: 2018 2017 United States Foreign United States Foreign (in thousands) Prior service cost, before tax $ — $ — $ 58 $ — Deferred taxes 560 — 539 — Total recognized in other comprehensive income, net of tax $ 560 $ — $ 597 $ —
Pension Plans with Accumulated Benefit Obligation and Projected Benefit Obligation in Excess of Plan Assets	Information for pension plans with an accumulated benefit obligation in excess of plan assets as of December 31: 2018 2017 United States Foreign United States Foreign (in millions) Projected benefit obligation $ 50.8 $ 39.1 $ 56.0 $ 39.4 Accumulated benefit obligation 48.6 35.6 51.6 34.7 Fair value of plan assets — 1.4 — 1.3
Net Periodic Pension and Postretirement Benefit Costs	For the years ended December 31, 2018, 2017, and 2016, Teradyne’s net periodic pension (income) cost was comprised of the following: 2018 2017 2016 United States Foreign United States Foreign United States Foreign (in thousands) Components of Net Periodic Pension (Income) Cost: Service cost $ 2,196 $ 786 $ 2,239 $ 818 $ 2,302 $ 761 Interest cost 8,940 687 13,151 852 13,630 1,185 Expected return on plan assets (9,049 ) (19 ) (12,008 ) (165 ) (13,830 ) (443 ) Amortization of prior service cost 58 — 70 — 96 — Net actuarial (gain) loss (4,429 ) 743 (6,712 ) (310 ) (4,013 ) 815 Settlement loss 345 — — — — — Total net periodic pension (income) cost $ (1,939 ) $ 2,197 $ (3,260 ) $ 1,195 $ (1,815 ) $ 2,318 Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Reversal of amortization items: Prior service cost (58 ) — (70 ) — (96 ) — Total recognized in other comprehensive income (58 ) — (70 ) — (96 ) — Total recognized in net periodic pension (income) cost and other comprehensive income $ (1,997 ) $ 2,197 $ (3,330 ) $ 1,195 $ (1,911 ) $ 2,318
Weighted Average Assumptions to Determine Net Periodic Cost and Benefit Obligation	Weighted Average Assumptions to Determine Net Periodic Pension Cost at January 1: 2018 2017 2016 United States Foreign United States Foreign United States Foreign Discount rate 3.4 % 1.8 % 3.9 % 1.8 % 4.0 % 2.3 % Expected return on plan assets 4.3 1.5 4.0 2.0 4.8 2.0 Salary progression rate 2.3 2.7 2.6 2.7 2.7 3.2 Weighted Average Assumptions to Determine Pension Obligations at December 31: 2018 2017 United States Foreign United States Foreign Discount rate 4.1 % 1.8 % 3.4 % 1.8 % Salary progression rate 2.3 2.6 2.3 2.7
Weighted Average Pension Asset Allocations by Category	The following table provides weighted average pension asset allocation by asset category at December 31, 2018 and 2017: 2018 2017 United States Foreign United States Foreign Fixed income securities 94.0 % — % 88.1 % — % Equity securities 5.0 — 9.9 — Other 1.0 100.0 2.0 100.0 100.0 % 100.0 % 100.0 % 100.0 %
Target Asset Allocation and Index for Each Asset Category	The target asset allocation and the index for each asset category for the U.S. Plan, per the investment policy, are as follows: Asset Category: Policy Index: Target Allocation U.S. corporate fixed income Barclays U.S. Corporate A or Better Index 75 % Global equity MSCI World Minimum Volatility Index 5 U.S. government fixed income Barclays Index 14 High yield fixed income Barclays U.S. Corporate High Yield 2% Issuer Cap Index 5 Cash Citigroup Three Month U.S. Treasury Bill Index 1
Changes in Fair Value of Pension Assets	The fair value of pension plan assets by asset category and by level at December 31, 2018 and December 31, 2017 were as follows: December 31, 2018 United States Foreign Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in thousands) Fixed income securities: Corporate debt securities $ — $ 115,424 $ — $ 115,424 $ — $ — $ — $ — U.S. government securities — 20,176 — 20,176 — — — — Global equity — 7,252 — 7,252 — — — — Other — — — — — 1,400 — 1,400 Cash and cash equivalents 1,449 — — 1,449 — — — — Total $ 1,449 $ 142,852 $ — $ 144,301 $ — $ 1,400 $ — $ 1,400 December 31, 2017 United States Foreign Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in thousands) Fixed income securities: Corporate debt securities $ — $ 260,294 $ — $ 260,294 $ — $ — $ — $ — U.S. government securities — 25,709 — 25,709 — — — — Global equity — 32,120 — 32,120 — — — — Group annuity insurance contracts — — 3,166 3,166 — — — — Other — — — — — 1,307 — 1,307 Cash and cash equivalents 3,217 — — 3,217 — — — — Total $ 3,217 $ 318,123 $ 3,166 $ 324,506 $ — $ 1,307 $ — $ 1,307
Expected Future Benefit Payments	Future benefit payments are expected to be paid as follows: United States Foreign (in thousands) 2019 $ 6,903 $ 874 2020 7,133 1,522 2021 8,026 905 2022 8,863 888 2023 9,584 1,199 2024-2028 57,120 5,921
Group Annuity Insurance Contracts
Changes in Fair Value of Pension Assets	Changes in the fair value of Level 3 group annuity insurance contracts for the years ended December 31, 2018 and 2017 were as follows: Group Annuity Insurance Contracts (in thousands) Balance at December 31, 2016 $ 29,456 Settlements (28,560 ) Interest and market value adjustments 959 Benefits paid (244 ) Other (61 ) Non-U.S. 1,616 Balance at December 31, 2017 3,166 Transfer out of Level 3 (2,658 ) Purchases of retiree annuity insurance contracts (512 ) Interest and market value adjustments 59 Benefits paid (40 ) Other (15 ) Balance at December 31, 2018 $ —
Postretirement Benefit Plans
Defined Benefit Pension and Postretirement Benefit Plan Assets and Obligations	The December 31 balances of the postretirement assets and obligations are shown below: 2018 2017 (in thousands) Assets and Obligations Change in benefit obligation: Projected benefit obligation: Beginning of year $ 6,177 $ 5,510 Service cost 39 34 Interest cost 196 201 Actuarial loss 25 398 Special termination benefits 3,708 591 Benefits paid (889 ) (557 ) End of year 9,256 6,177 Change in plan assets: Fair value of plan assets: Beginning of year — — Company contributions 889 557 Benefits paid (889 ) (557 ) End of year — — Funded status $ (9,256 ) $ (6,177 )
Amounts Recorded within Statement of Financial Position	The following table provides amounts recorded within the account line items of financial position as of December 31: 2018 2017 (in thousands) Accrued employees’ compensation and withholdings $ (1,310 ) $ (591 ) Retirement plans liability (7,946 ) (5,586 ) Funded status $ (9,256 ) $ (6,177 )
Amounts Recognized in Accumulated Other Comprehensive Income	The following table provides amounts recognized in accumulated other comprehensive income as of December 31: 2018 2017 (in thousands) Prior service credit, before tax $ (249 ) $ (622 ) Deferred taxes (1,641 ) (1,472 ) Total recognized in other comprehensive income, net of tax $ (1,890 ) $ (2,094 )
Net Periodic Pension and Postretirement Benefit Costs	For the years ended December 31, 2018, 2017, and 2016, Teradyne’s net periodic postretirement benefit cost (income) was comprised of the following: 2018 2017 2016 (in thousands) Components of Net Periodic Postretirement Benefit Cost (income): Service cost $ 39 $ 34 $ 37 Interest cost 196 201 218 Amortization of prior service credit (373 ) (496 ) (607 ) Net actuarial loss 25 398 5 Special termination benefits 3,708 591 — Total net periodic postretirement benefit cost (income) 3,595 728 (347 ) Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Prior service cost — — (93 ) Reversal of amortization items: Prior service credit 373 496 607 Total recognized in other comprehensive income 373 496 514 Total recognized in net periodic postretirement benefit cost (income) and other comprehensive income $ 3,968 $ 1,224 $ 167
Weighted Average Assumptions to Determine Net Periodic Cost and Benefit Obligation	Weighted Average Assumptions to Determine Net Periodic Postretirement Benefit Income as of January 1: 2018 2017 2016 Discount rate 3.4 % 3.9 % 3.9 % Initial health care cost trend rate 7.9 7.3 7.5 Ultimate health care cost trend rate 4.5 5.0 5.0 Year in which ultimate health care cost trend rate is reached 2026 2023 2023 Weighted Average Assumptions to Determine Postretirement Benefit Obligation as of December 31: 2018 2017 2016 Discount rate 4.0 % 3.4 % 3.9 % Initial medical trend 7.5 7.9 7.3 Ultimate health care trend 4.5 4.5 5.0 Medical cost trend rate decrease to ultimate rate in year 2026 2026 2023
Expected Future Benefit Payments	Future benefit payments are expected to be paid as follows: Benefit Payments (in thousands) 2019 $ 1,310 2020 1,234 2021 1,181 2022 984 2023 811 2024-2028 2,364
One Percentage Point Change in Assumed Health Care Cost Trend Rates for Year	A one percentage point change in the assumed health care cost trend rates for the year ended December 31, 2018 would have the following effects: 1 Percentage Point Increase 1 Percentage Point Decrease (in thousands) Effect on total service and interest cost components $ 7 $ (7 ) Effect on postretirement benefit obligations 181 (171 )

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions	The fair value was estimated using the Monte Carlo simulation model with the following assumptions: 2018 2017 2016 Risk-free interest rate 2.2 % 1.5 % 1.0 % Teradyne volatility-historical 26.8 % 26.6 % 27.0 % NYSE Composite Index volatility-historical 12.4 % 13.4 % 13.1 % Dividend yield 0.8 % 1.0 % 1.2 %
Fair Value of Stock Options Using Assumptions	The fair value of the stock options at grant date was estimated using the Black-Scholes option-pricing model with the following assumptions: 2018 2017 2016 Expected life (years) 5.0 5.0 5.0 Risk-free interest rate 2.4 % 2.0 % 1.4 % Volatility-historical 26.4 % 27.8 % 32.9 % Dividend yield 0.80 % 1.00 % 1.20 %
Stock Compensation Plan Activity	Stock compensation plan activity for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 (in thousands) Restricted Stock Units: Non-vested 3,174 3,778 4,070 Awarded 790 939 1,471 Vested (1,382 ) (1,434 ) (1,530 ) Forfeited (128 ) (109 ) (233 ) Non-vested 2,454 3,174 3,778 Stock Options: Outstanding at January 1 531 926 1,121 Granted 69 111 130 Exercised (94 ) (501 ) (324 ) Expired — (5 ) (2 ) Outstanding at December 31 506 531 926 Vested and expected to vest at December 31 506 531 926 Exercisable at December 31 256 233 598
Share Based Compensation Total Shares Available	Total shares available for the years 2018, 2017, and 2016: 2018 2017 2016 (in thousands) Shares available: Available for grant at January 1 8,605 9,546 10,914 Options granted (69 ) (111 ) (130 ) Restricted stock units awarded (790 ) (939 ) (1,471 ) Restricted stock units forfeited 128 109 233 Available for grant at December 31 7,874 8,605 9,546
Weighted-Average Restricted Stock Unit Award Date Fair Value	Weighted average restricted stock unit award date fair value information for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 Non-vested $ 21.71 $ 18.27 $ 17.66 Awarded 45.99 28.91 18.95 Vested 20.20 17.90 17.36 Forfeited 24.67 20.35 17.80 Non-vested $ 29.22 $ 21.71 $ 18.27
Restricted Stock Unit Awards Aggregate Intrinsic Value	Restricted stock unit awards aggregate intrinsic value information at December 31 for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 (in thousands) Vested $ 63,688 $ 40,649 $ 30,008 Outstanding 77,015 132,875 95,952 Expected to vest 77,187 130,594 91,871
Restricted Stock Units Weighted Average Remaining Contractual Terms	Restricted stock units weighted average remaining contractual terms (in years) information at December 31, for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 Outstanding 0.92 1.00 1.04 Expected to vest 0.91 0.99 1.03
Weighted Average Stock Options Exercise Price	Weighted average stock options exercise price information for the year ended December 31, 2018 is as follows: 2018 Outstanding at January 1 $ 13.92 Options granted 47.70 Options exercised 10.89 Outstanding at December 31 19.06 Exercisable at December 31 8.31
Stock Option Aggregate Intrinsic Value Information	Stock option aggregate intrinsic value information for the years ended December 31, 2018, 2017, and 2016 is as follows: 2018 2017 2016 (in thousands) Exercised $ 2,960 $ 8,035 $ 3,729 Outstanding 7,359 14,831 12,468 Vested and expected to vest 7,359 14,831 12,468 Exercisable 5,905 9,076 10,217
Stock Options Weighted Average Remaining Contractual Terms	Stock options weighted average remaining contractual terms (in years) information at December 31, for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 Outstanding 3.6 4.1 3.9 Vested and expected to vest 3.6 4.1 3.9 Exercisable 2.4 2.8 3.2
Significant Option Groups Outstanding	Significant option groups outstanding at December 31, 2018 and related weighted average price and remaining contractual life information follow: Options Outstanding Options Exercisable Range Of Exercise Prices Weighted- Average Remaining Contractual Life (Years) Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price (shares in thousands) $1.48 – $2.58 1.23 67 $ 1.83 67 $ 1.83 $2.67 – $3.28 2.20 103 2.69 103 2.69 $7.71 – $19.43 3.41 166 18.59 68 18.02 $28.56 – $47.70 5.62 170 36.30 18 28.56 506 $ 19.06 256 $ 8.31
Effect to Income (Loss) from Operations for Recording Stock-Based Compensation	The following table provides the effect to income from operations for recording stock-based compensation for the years ended December 31, 2018, 2017, and 2016: 2018 2017 2016 (in thousands) Cost of revenues $ 3,129 $ 3,212 $ 3,153 Engineering and development 9,181 9,370 9,458 Selling and administrative 21,267 21,515 18,139 Stock-based compensation 33,577 34,097 30,750 Income tax benefit (12,036 ) (10,462 ) (8,752 ) Total stock-based compensation expense after income taxes $ 21,541 $ 23,635 $ 21,998

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Income (Loss) Before Income Taxes and Provision (Benefit) for Income Taxes from Operations	The components of income (loss) before income taxes and the provision (benefit) for income taxes as shown in the consolidated statements of operations were as follows: 2018 2017 2016 (in thousands) Income (loss) before income taxes: U.S. $ 189,691 $ 76,699 $ (341,018 ) Non-U.S. 278,110 447,713 285,958 $ 467,801 $ 524,412 $ (55,060 ) Provision (benefit) for income taxes: Current: U.S. Federal $ (59,122 ) $ 162,679 $ 7,750 Non-U.S. 45,083 64,313 41,579 State 1,721 2,623 1,968 (12,318 ) 229,615 51,297 Deferred: U.S. Federal 29,252 43,687 (51,482 ) Non-U.S. (1,243 ) (6,476 ) (9,240 ) State 331 (106 ) (2,214 ) 28,340 37,105 (62,936 ) Total provision (benefit) for income taxes: $ 16,022 $ 266,720 $ (11,639 )
Reconciliation of Effective Tax Rate	A reconciliation of the effective tax rate for the years 2018, 2017, and 2016 is as follows: 2018 2017 2016 U.S. statutory federal tax rate 21.0 % 35.0 % 35.0 % U.S. transition tax (10.5 ) 28.7 — U.S. foreign derived intangible income (1.8 ) — — Impact of rate change on deferred tax 0.3 6.9 — Uncertain tax positions 1.0 1.7 (2.6 ) Foreign taxes (2.0 ) (16.3 ) 78.0 Foreign tax credits (2.2 ) (2.2 ) 49.1 U.S. research and development credit (2.2 ) (1.6 ) 15.8 Equity compensation (1.2 ) (0.8 ) (2.7 ) State income taxes, net of federal tax benefit 0.1 (0.4 ) 2.3 Domestic production activities deduction — (0.3 ) 2.3 Goodwill impairment — — (162.1 ) U.S. alternative minimum tax credit — — 3.7 Inventory cost capitalization — — 1.8 Other, net 0.9 0.2 0.5 3.4 % 50.9 % 21.1 %
Deferred Tax Assets (Liabilities)	Significant components of Teradyne’s deferred tax assets (liabilities) as of December 31, 2018 and 2017 were as follows: 2018 2017 (in thousands) Deferred tax assets: Tax credits $ 69,091 $ 76,083 Accruals 23,449 27,508 Pension liabilities 20,826 22,602 Inventory valuations 18,514 17,793 Deferred revenue 9,130 9,016 Equity compensation 7,190 6,861 Vacation accrual 4,772 4,747 Net operating loss carryforwards 3,658 5,440 Marketable securities 962 — Other 685 713 Gross deferred tax assets 158,277 170,763 Less: valuation allowance (69,852 ) (63,919 ) Total deferred tax assets $ 88,425 $ 106,844 Deferred tax liabilities: Intangible assets $ (24,211 ) $ (16,120 ) Depreciation (14,028 ) (12,293 ) Marketable securities — (1,125 ) Total deferred tax liabilities $ (38,239 ) $ (29,538 ) Net deferred assets $ 50,186 $ 77,306
Operating Loss Carryforwards	At December 31, 2018, Teradyne had operating loss carryforwards that expire in the following years: State Operating Loss Carryforwards Foreign Operating Loss Carryforwards (in thousands) 2019 $ 258 $ — 2020 269 — 2021 2,977 — 2022 5,749 — 2023 6,241 — 2024-2028 4,672 — 2029-2033 22,724 44 Beyond 2033 5,305 72 Non-expiring — 4,389 Total $ 48,195 $ 4,505
Unrecognized Tax Benefits	Teradyne’s gross unrecognized tax benefits for the years ended December 31, 2018, 2017, and 2016 were as follows: 2018 2017 2016 (in thousands) Beginning balance, as of January 1 $ 36,263 $ 38,958 $ 36,792 Additions: Tax positions for current year 4,716 8,208 9,766 Tax positions for prior years 2,626 199 187 Reductions: Tax positions for prior years (153 ) (10,573 ) (1,960 ) Expiration of statutes (57 ) (325 ) (3,532 ) Settlements with tax authorities — (204 ) (2,295 ) Ending balance as of December 31 $ 43,395 $ 36,263 $ 38,958

Operating Segment, Geographic_2

Operating Segment, Geographic and Significant Customer Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Information	Segment information for the years ended December 31, 2018, 2017, and 2016 is as follows: Semiconductor Test System Test Industrial Automation Wireless Test Corporate And Other Consolidated (in thousands) 2018 Revenues $ 1,492,417 $ 216,132 $ 261,452 $ 132,006 $ (1,205 ) $ 2,100,802 Income (loss) before taxes (1)(2) 397,645 48,857 7,670 29,052 (15,423 ) 467,801 Total assets (3) 669,452 88,098 607,502 77,570 1,263,984 2,706,606 Property additions 94,496 3,469 11,188 5,226 — 114,379 Depreciation and amortization expense 58,095 6,430 36,755 5,328 6,616 113,224 2017 Revenues $ 1,662,549 $ 192,135 $ 170,056 $ 111,866 $ — $ 2,136,606 Income (loss) before taxes (1)(2) 491,361 10,305 8,763 17,350 (3,368 ) 524,411 Total assets (3) 597,480 97,018 368,037 59,912 1,987,098 3,109,545 Property additions 87,920 5,976 7,044 4,435 — 105,375 Depreciation and amortization expense 58,901 6,646 25,711 5,392 11,425 108,075 2016 Revenues $ 1,368,169 $ 189,846 $ 99,031 $ 96,204 $ — $ 1,753,250 Income (loss) before taxes (1)(2) 311,939 28,916 (16,783 ) (371,409 ) (7,723 ) (55,060 ) Total assets (3) 557,546 110,361 317,635 62,366 1,714,585 2,762,493 Property additions 70,543 3,788 6,755 4,186 — 85,272 Depreciation and amortization expense 58,087 6,551 26,869 25,921 2,581 120,009 (1) Included in Corporate and Other are: contingent consideration adjustments, pension and postretirement plans actuarial gains (losses), severance charges, impairment of fixed assets and expenses related to the Japan earthquake, property insurance recovery, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations and acquisition related charges. (2) Included in income (loss) before taxes are charges and credits related to restructuring and other, and inventory charges. In 2016, loss before income taxes in Wireless Test also included charges related to goodwill and acquired intangible assets impairment. (3) Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.
Revenues by Country	Information as to Teradyne’s revenues by country is as follows: 2018 2017 2016 (in thousands) Revenues from customers (1): Taiwan $ 516,322 $ 687,031 $ 653,076 China 348,942 260,451 174,876 United States 282,869 252,516 221,948 Europe 223,207 163,715 117,671 Korea 163,224 206,819 147,882 Japan 158,281 169,093 135,978 Malaysia 122,797 124,048 103,472 Singapore 108,618 101,085 73,172 Philippines 77,996 105,850 54,705 Thailand 59,184 29,566 43,097 Rest of the World 39,362 36,432 27,373 $ 2,100,802 $ 2,136,606 $ 1,753,250 (1) Revenues attributable to a country are based on location of customer site.
Long-Lived Assets by Geographic Area	Long-lived assets by geographic area: United States Foreign(1) Total (in thousands) December 31, 2018 $ 209,368 $ 70,453 $ 279,821 December 31, 2017 $ 198,855 $ 69,592 $ 268,447 (1) As of December 31, 2018 and 2017, long-lived assets attributable to Singapore were $19.4 million and $23.6 million, respectively.
Wireless Test
Schedule of Segment Reporting Information by Segment Charges	Included in the Wireless Test segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Cost of revenues—inventory charge $ 2,565 $ 2,190 $ 7,207 Restructuring and other—lease impairment — 972 — Restructuring and other—employee severance — — 2,650 Goodwill impairment charge — — 254,946 Intangible assets impairment charge — — 83,339
Semiconductor Test
Schedule of Segment Reporting Information by Segment Charges	Included in the Semiconductor Test segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Restructuring and other—employee severance $ 8,429 $ 1,779 $ 2,860 Cost of revenues—inventory charge 6,822 4,606 9,656 Restructuring and other—impairment of fixed assets — 1,124 —
System Test
Schedule of Segment Reporting Information by Segment Charges	Included in the System Test segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Cost of revenues—inventory charge $ 1,175 $ 1,918 $ 630
Industrial Automation
Schedule of Segment Reporting Information by Segment Charges	Included in the Industrial Automation segment are charges in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Restructuring and other—acquisition related expenses and compensation $ 1,163 $ — $ — Cost of revenues—inventory charge 680 — — Restructuring and other—employee severance — 1,414 585
Corporate And Eliminations
Schedule of Segment Reporting Information by Segment Charges	Included in Corporate and Other are charges and credits in the following accounts: For the Year Ended December 31, 2018 2017 2016 (in thousands) Restructuring and other—MiR contingent consideration adjustment $ 17,666 $ — $ — Restructuring and other—Universal Robots contingent consideration adjustment (16,679 ) 7,820 15,346 Restructuring and other—acquisition related expenses 3,422 — — Restructuring and other 872 — — Restructuring and other—expense related to Japan earthquake and impairment of fixed assets — 755 5,051 Restructuring and other—property insurance recovery — (5,064 ) (5,051 )

Supplementary Information (Tabl

Supplementary Information (Tables)	12 Months Ended
	Dec. 31, 2018
Consolidated Quarterly Statements of Operations	The following sets forth certain unaudited consolidated quarterly statements of operations data for each of Teradyne’s last eight quarters. In management’s opinion, this quarterly information reflects all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement for the periods presented. Such quarterly results are not necessarily indicative of future results of operations and should be read in conjunction with the audited consolidated financial statements of Teradyne and the notes thereto included elsewhere herein. 2018 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter (1) (2)(5) (3)(5) (4)(5) (in thousands, except per share amounts) Revenues: Products $ 403,925 $ 434,051 $ 470,994 $ 420,652 Services 83,542 92,878 95,854 98,906 Total revenues 487,467 526,929 566,848 519,558 Cost of revenues: Cost of products 180,958 180,777 195,339 170,064 Cost of services 36,677 38,818 37,816 39,959 Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below) 217,635 219,595 233,155 210,023 Gross profit 269,832 307,334 333,693 309,535 Operating expenses: Selling and administrative 90,505 99,410 100,202 100,552 Engineering and development 74,408 75,342 77,049 74,706 Acquired intangible assets amortization 7,698 9,793 11,142 10,558 Restructuring and other (313 ) 2,389 1,710 11,446 Total operating expenses 172,298 186,934 190,103 197,262 Income (loss) from operations 97,534 120,400 143,590 112,273 Non-operating Interest income (5,981 ) (5,427 ) (6,213 ) (9,083 ) Interest expense 6,890 5,639 5,557 13,182 Other (income) expense, net 805 176 3,405 (2,954 ) Income (loss) before income taxes 95,820 120,012 140,841 111,128 Income tax provision (benefit) 8,846 18,975 20,863 (32,662 ) Net income (loss) $ 86,974 $ 101,037 $ 119,978 $ 143,790 Net income (loss) per common share—basic $ 0.45 $ 0.53 $ 0.65 $ 0.80 Net income (loss) per common share—diluted $ 0.43 $ 0.52 $ 0.63 $ 0.79 Cash dividend declared per common share $ 0.09 $ 0.09 $ 0.09 $ 0.09 (1) 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. (2) 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. (3) 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. (4) 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. (5) Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy. 2017 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter (1) (2)(5) (3) (4)(5) (in thousands, except per share amounts) Revenues: Products $ 373,204 $ 610,356 $ 412,854 $ 388,282 Services 83,709 86,545 90,524 91,133 Total revenues 456,913 696,901 503,378 479,415 Cost of revenues: Cost of products 154,883 267,752 169,661 168,672 Cost of services 37,014 38,511 38,848 39,813 Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below) 191,897 306,263 208,509 208,485 Gross profit 265,016 390,638 294,869 270,930 Operating expenses: Selling and administrative 84,792 90,111 86,130 87,880 Engineering and development 75,978 82,270 76,986 72,070 Acquired intangible assets amortization 7,952 8,166 7,028 7,384 Restructuring and other 2,511 2,288 (4,407 ) 8,970 Total operating expenses 171,233 182,835 165,737 176,304 Income from operations 93,783 207,803 129,132 94,626 Non-operating Interest income (3,520 ) (3,292 ) (4,517 ) (6,476 ) Interest expense 5,402 5,509 5,372 5,380 Other (income) expense, net (115 ) (1,291 ) 840 (2,362 ) Income before income taxes 92,016 206,877 127,437 98,084 Income tax provision 6,795 31,901 24,017 204,007 Net income (loss) $ 85,221 $ 174,976 $ 103,420 $ (105,923 ) Net income (loss) per common share—basic $ 0.43 $ 0.88 $ 0.52 $ (0.54 ) Net income (loss) per common share—diluted $ 0.42 $ 0.87 $ 0.52 $ (0.54 ) Cash dividend declared per common share $ 0.07 $ 0.07 $ 0.07 $ 0.07 (1) Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges. (2) Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges. (3) Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges. (4) Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets. (5) Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

The Company - Additional inform

The Company - Additional information (Detail) - USD ($)	Apr. 25, 2018	Feb. 26, 2018	Jun. 11, 2015	Dec. 31, 2018
Business Acquisition [Line Items]
Contingent consideration				$ 31,000,000
Universal Robots (UR)
Business Acquisition [Line Items]
Cash paid to acquire outstanding common and preferred stock			$ 284,000,000
Arrangement range of outcomes value high			$ 65,000,000
Energid Technologies Corporation
Business Acquisition [Line Items]
Total purchase price		$ 28,000,000
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Cash paid to acquire outstanding common and preferred stock	$ 145,200,000
Arrangement range of outcomes value high				$ 115,000,000
Total purchase price	197,778,000
Contingent consideration	$ 52,600,000

Accounting Policies - Additiona

Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

[3],[4]

Jul. 01, 2018

[3],[5]

Apr. 01, 2018

[6]

Dec. 31, 2017

Oct. 01, 2017

[8],[9]

Jul. 02, 2017

[8],[10]

Apr. 02, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Jan. 01, 2018

Summary Of Significant Accounting Policies [Line Items]

Revenue recognized in accordance with ASC 606

[1]

$ 2,100,802

$ 2,136,606

$ 1,753,250

Revenue on leases

$ 12,000

Standard warranty period

12 months

Depreciation over life to cost of revenues and selling and administrative expenses, years

6 years

Net book value of internally manufactured test systems sold

$ 3,800

3,600

11,400

Cumulative effect adjustment to increase retained earnings and deferred tax assets

$ 12,679

12,679

Income tax provision (benefit)

(32,662)

[2],[3]

$ 20,863

$ 18,975

$ 8,846

$ 204,007

[7],[8]

$ 24,017

$ 31,901

$ 6,795

[11]

16,022

266,720

(11,639)

Advertising costs

15,400

9,100

6,400

Losses (gains) on foreign currency transactions

(2,400)

2,900

(8,000)

Trade Accounts Receivable

52,200

5,400

52,200

5,400

Deferred Revenue And Customer Advances

$ 110,461

$ 113,741

$ 110,461

113,741

Short-term Contract with Customer [Member]

Summary Of Significant Accounting Policies [Line Items]

Revenue, Remaining Performance Obligation, Percentage

70.00%

70.00%

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period

12 months

Long-term Contract with Customer [Member]

Summary Of Significant Accounting Policies [Line Items]

Revenue, Remaining Performance Obligation, Percentage

25.00%

25.00%

Long-term Contract with Customer [Member] | Maximum [Member]

Summary Of Significant Accounting Policies [Line Items]

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period

3 years

Long-term Contract with Customer [Member] | Minimum [Member]

Summary Of Significant Accounting Policies [Line Items]

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period

1 year

ASU 2014-09

Summary Of Significant Accounting Policies [Line Items]

Revenue recognized in accordance with ASC 606

$ 2,088,800

ASU 2016-09

Summary Of Significant Accounting Policies [Line Items]

Cumulative effect adjustment to increase retained earnings and deferred tax assets

$ 39

Income tax provision (benefit)

(6,300)

ASU 2017-07

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in income from operations

$ (5,000)

$ (3,000)

Retained Earnings

Summary Of Significant Accounting Policies [Line Items]

Cumulative effect adjustment to increase retained earnings and deferred tax assets

$ 12,679

$ 12,679

Retained Earnings | ASU 2014-09

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in adoption of new accounting guidance amount

$ 12,700

Retained Earnings | ASU 2016-01

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in adoption of new accounting guidance amount

3,100

Accumulated Other Comprehensive Income (Loss) | ASU 2016-01

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in adoption of new accounting guidance amount

$ (3,100)

[1]

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

[2]

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.

[3]

Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[4]

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.

[5]

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.

[6]

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.

[7]

Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.

[8]

Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[9]

Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.

[10]

Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.

[11]

Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Disaggregated Revenue by Primar

Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total	[1]	$ 2,100,802	$ 2,136,606	$ 1,753,250
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		1,492,417	1,662,549	1,368,169
System Test
Disaggregation of Revenue [Line Items]
Total		216,132	192,135	189,846
Industrial Automation
Disaggregation of Revenue [Line Items]
Total		261,452	170,056	99,031
Wireless Test
Disaggregation of Revenue [Line Items]
Total		132,006	$ 111,866	$ 96,204
Corporate and Other
Disaggregation of Revenue [Line Items]
Total		(1,205)
Americas | Point in Time
Disaggregation of Revenue [Line Items]
Total		219,755
Americas | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		17,730
Americas | Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total		(1,205)
Americas | Over Time
Disaggregation of Revenue [Line Items]
Total		68,624
Americas | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		1,436
Europe, Middle East and Africa | Point in Time
Disaggregation of Revenue [Line Items]
Total		200,939
Europe, Middle East and Africa | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		3,821
Europe, Middle East and Africa | Over Time
Disaggregation of Revenue [Line Items]
Total		35,038
Europe, Middle East and Africa | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		1,147
Asia Pacific
Disaggregation of Revenue [Line Items]
Total		12,037
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total		760
Asia Pacific | Point in Time
Disaggregation of Revenue [Line Items]
Total		1,394,477
Asia Pacific | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		100,985
Asia Pacific | Over Time
Disaggregation of Revenue [Line Items]
Total		169,932
Asia Pacific | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		6,127
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		1,218,949
SOC | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		43,398
SOC | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		35,100
SOC | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		50,988
SOC | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		21,584
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		10,885
SOC | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		916,107
SOC | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		140,887
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		273,468
Memory | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		14,579
Memory | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		2,774
Memory | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		9,726
Memory | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		1,125
Memory | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		235,061
Memory | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		10,203
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total		92,737
Defense/Aerospace | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		59,246
Defense/Aerospace | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		24,577
Defense/Aerospace | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		3,056
Defense/Aerospace | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		2,124
Defense/Aerospace | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		2,769
Defense/Aerospace | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		965
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total		66,648
Storage Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		767
Storage Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		58,004
Storage Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		7,877
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total		56,747
Production Board Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		9,082
Production Board Test | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		3,091
Production Board Test | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		16,733
Production Board Test | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		6,467
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total		392
Production Board Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		17,761
Production Board Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		3,221
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		234,095
Universal Robots (UR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		68,289
Universal Robots (UR) | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		649
Universal Robots (UR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		105,776
Universal Robots (UR) | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		1,000
Universal Robots (UR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		57,830
Universal Robots (UR) | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		551
Mobile Industrial Robots (MiR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		24,115
Mobile Industrial Robots (MiR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		7,326
Mobile Industrial Robots (MiR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		10,839
Mobile Industrial Robots (MiR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		5,950
Energid Technologies Corporation | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		3,242
Energid Technologies Corporation | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		543
Energid Technologies Corporation | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		997
Energid Technologies Corporation | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		1,591
Energid Technologies Corporation | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		10
Energid Technologies Corporation | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		$ 101
[1]	Revenues attributable to a country are based on location of customer site.

Information about Contract Liab

Information about Contract Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue and customer advances	$ 77,711		$ 83,614
Long-term deferred revenue and customer advances	32,750		$ 30,127
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue and customer advances	73,593	$ 76,638
Long-term deferred revenue and customer advances	22,447	20,848
ASU 2014-09 | Adjustments to Recognize Under Legacy GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue and customer advances	(4,118)	1,073
Long-term deferred revenue and customer advances	$ (10,303)	$ 11,902

Summarize Impact of ASC 606 to

Summarize Impact of ASC 606 to Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Accounts receivable, less allowance for doubtful accounts	$ 291,267		$ 272,783
Inventories, net	153,541		107,525
Deferred tax assets	70,848		84,026
LIABILITIES
Deferred revenue and customer advances	77,711		83,614
Income taxes payable	36,185		59,055
Long-term deferred revenue and customer advances	32,750		30,127
Shareholders' equity
Accumulated deficit	(158,191)		$ 272,013
ASU 2014-09
Assets
Accounts receivable, less allowance for doubtful accounts	253,919
Inventories, net	164,300
Deferred tax assets	66,974
LIABILITIES
Deferred revenue and customer advances	73,593	$ 76,638
Income taxes payable	31,690
Long-term deferred revenue and customer advances	22,447	20,848
Shareholders' equity
Accumulated deficit	(169,738)
ASU 2014-09 | Adjustments to Recognize Under Legacy GAAP
Assets
Accounts receivable, less allowance for doubtful accounts	(37,348)
Inventories, net	10,759
Deferred tax assets	(3,874)
LIABILITIES
Deferred revenue and customer advances	(4,118)	1,073
Income taxes payable	(4,495)
Long-term deferred revenue and customer advances	(10,303)	$ 11,902
Shareholders' equity
Accumulated deficit	$ (11,547)

Summarize Impact of ASC 606 t_2

Summarize Impact of ASC 606 to Condensed Consolidated Statement of Operation (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2018	[2],[3]	Sep. 30, 2018	[3],[4]	Jul. 01, 2018	[3],[5]	Apr. 01, 2018	[6]	Dec. 31, 2017	[7],[8]	Oct. 01, 2017	[8],[9]	Jul. 02, 2017	[8],[10]	Apr. 02, 2017	[11]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	[1]																	$ 2,100,802	$ 2,136,606	$ 1,753,250
Total cost of revenues																		880,408
Income tax provision		$ (32,662)		$ 20,863		$ 18,975		$ 8,846		$ 204,007		$ 24,017		$ 31,901		$ 6,795		16,022	266,720	(11,639)
Net income		$ 143,790		$ 119,978		$ 101,037		$ 86,974		$ (105,923)		$ 103,420		$ 174,976		$ 85,221		$ 451,779	$ 257,692	$ (43,421)
Net income per common share:
Basic		$ 0.80		$ 0.65		$ 0.53		$ 0.45		$ (0.54)		$ 0.52		$ 0.88		$ 0.43		$ 2.41	$ 1.30	$ (0.21)
Diluted		$ 0.79		$ 0.63		$ 0.52		$ 0.43		$ (0.54)		$ 0.52		$ 0.87		$ 0.42		$ 2.35	$ 1.28	$ (0.21)
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues																		$ 2,088,800
ASU 2014-09 | Adjustments to Recognize Under Legacy GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues																		(39,184)
Total cost of revenues																		(10,760)
Income tax provision																		(4,197)
Net income																		$ (24,227)
Net income per common share:
Basic																		$ (0.13)
Diluted																		$ (0.13)
ASU 2014-09 | Legacy GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues																		$ 2,061,618
Total cost of revenues																		869,648
Income tax provision																		11,825
Net income																		$ 427,552
Net income per common share:
Basic																		$ 2.28
Diluted																		$ 2.22
[1]	Revenues attributable to a country are based on location of customer site.
[2]	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.
[3]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[4]	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.
[5]	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.
[6]	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.
[7]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[8]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[9]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[10]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[11]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Deferred Revenue and Customer A

Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Revenue Arrangement
Maintenance and training	$ 58,362	$ 57,256
Extended warranty	27,422	24,438	$ 28,200	$ 30,024
Customer advances, undelivered elements and other	24,677	32,047
Total deferred revenue and customer advances	$ 110,461	$ 113,741

Warranty Accrual Included in Ot

Warranty Accrual Included in Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 8,200	$ 7,203	$ 6,925
Acquisition	41
Accruals for warranties issued during the period	13,045	14,223	14,291
Accruals related to pre-existing warranties	921	(379)	(1,354)
Settlements made during the period	(14,298)	(12,847)	(12,659)
Balance at end of period	$ 7,909	$ 8,200	$ 7,203

Extended Product Warranty of Sh

Extended Product Warranty of Short and Long-Term Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 24,438	$ 28,200	$ 30,024
Deferral of new extended warranty revenue	23,753	20,513	19,909
Recognition of extended warranty deferred revenue	(20,769)	(24,275)	(21,733)
Balance at end of period	$ 27,422	$ 24,438	$ 28,200

Schedule of Prepayments and Oth

Schedule of Prepayments and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid And Other Current Assets [Line Items]
Contract manufacturer and supplier prepayments	$ 131,642	$ 82,503
Prepaid taxes	9,646	5,039
Prepaid maintenance and other services	8,487	8,189
Other prepayments	12,744	12,386
Total prepayments	$ 162,519	$ 108,117

Useful Lives of Assets (Detail)

Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2018
Buildings
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	40 years
Building Improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	5 years
Building Improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	10 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Useful lives, description	Lesser of lease term or 10 years
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	10 years
Test Systems Manufactured Internally
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	6 years
Machinery and Equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	3 years
Machinery and Equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	5 years
Software | Minimum
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	3 years
Software | Maximum
Property, Plant and Equipment [Line Items]
Useful lives, maximum years	5 years

Recently Issued Accounting Pr_2

Recently Issued Accounting Pronouncements - Additional Information (Detail) - Scenario, Forecast [Member] $ in Millions	Jan. 31, 2019USD ($)
Operating Lease, Right-of-Use Asset	$ 50
Operating Lease, Liability	$ 60

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($)	Apr. 25, 2018	Feb. 26, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Contingent consideration			$ 31,000,000	$ 31,000,000
Revenues			24,100,000
Income (loss) before income taxes			(7,600,000)
Goodwill			381,850,000	381,850,000	$ 252,011,000	$ 223,343,000
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Total preliminary purchase price	$ 197,778,000
Cash paid to acquire outstanding common and preferred stock	145,200,000
Contingent consideration	52,600,000
Arrangement range of outcomes value high			$ 115,000,000	115,000,000
Goodwill, not deductible for tax purposes	136,000,000
Net income				450,559,000	243,399,000
Goodwill	$ 135,976,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 2 months 12 days
Mobile Industrial Robots (MiR) | Fair Value Adjustment to Inventory
Business Acquisition [Line Items]
Net income				400,000	2,900,000
Mobile Industrial Robots (MiR) | Acquisition Related Costs
Business Acquisition [Line Items]
Net income				$ 2,900,000	$ 400,000
Energid Technologies Corporation
Business Acquisition [Line Items]
Total preliminary purchase price		$ 28,000,000
Goodwill		14,400,000
Acquired value of intangible assets		$ 12,300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		7 years 8 months 12 days
Net tangible assets		$ 1,000,000

Final Allocation of Purchase Pr

Final Allocation of Purchase Price (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Apr. 25, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 381,850		$ 252,011	$ 223,343
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Goodwill		$ 135,976
Intangible assets		80,670
Current assets		6,039
Non-current assets		1,336
Accounts payable and current liabilities		(7,336)
Long-term deferred tax liabilities		(18,007)
Other long-term liabilities		(900)
Total purchase price		$ 197,778

Components of Intangible Assets

Components of Intangible Assets and Their Estimated Useful Lives at Acquisition Date (Detail) - Mobile Industrial Robots (MiR) - USD ($) $ in Thousands	Apr. 25, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 80,670	$ 80,700
Total intangible assets, estimated useful life, years	7 years 2 months 12 days
Developed technology
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 58,900
Total intangible assets, estimated useful life, years	7 years
Trademarks and tradenames
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 13,240
Total intangible assets, estimated useful life, years	11 years
Customer Relationships
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 8,500
Total intangible assets, estimated useful life, years	2 years 6 months
Customer backlog
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 30
Total intangible assets, estimated useful life, years	2 months 12 days

Pro Forma Results Under Acquisi

Pro Forma Results Under Acquisition (Detail) - Mobile Industrial Robots (MiR) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Revenues	$ 2,107,600	$ 2,148,320
Net income	$ 450,559	$ 243,399
Net income per common share, basic	$ 2.40	$ 1.23
Net income per common share, diluted	$ 2.34	$ 1.21

Composition of Inventories, Net

Composition of Inventories, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory [Line Items]
Raw material	$ 89,365	$ 62,668
Work-in-process	31,014	19,464
Finished goods	33,162	25,393
Inventories, net	$ 153,541	$ 107,525

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Inventory [Line Items]
Inventory reserves	$ 100.8	$ 102.9

Property Plant and Equipment, N

Property Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Land	$ 16,561	$ 16,561
Buildings	105,935	98,369
Machinery and equipment	689,770	647,961
Furniture and fixtures, and software	90,384	88,539
Leasehold improvements	52,536	49,540
Construction in progress	6,276	13,522
Property, Plant and Equipment, Gross, Total	961,462	914,492
Less: accumulated depreciation	681,641	646,045
Property, plant and equipment, net	$ 279,821	$ 268,447

Property, Plant and Equipment -

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation of property, plant and equipment	$ 67,415	$ 66,122	$ 64,782
Machinery and equipment	689,770	647,961
Accumulated depreciation	681,641	646,045
Test Systems Leased By Customers
Property, Plant and Equipment [Line Items]
Machinery and equipment	5,500	18,100
Accumulated depreciation	$ 5,200	$ 13,700

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financial Instruments and Fair Value [Line Items]
Available-for-sale securities, realized gain	$ 4,000,000	$ 1,100,000	$ 1,600,000
Available-for-sale securities, realized loss	1,600,000	300,000	500,000
Unrealized loss related to equity securities	6,000,000
Available-for-sale marketable securities, Fair Market Value of Investments in debt securities with Unrealized Losses	191,978,000	1,350,896,000
Fair market value of investments with unrealized losses greater than one year	28,500,000	141,000,000
Aggregate loss of investments with unrealized losses greater than one year	1,600,000	1,200,000
Fair market value of investments with unrealized losses less than one year	163,500,000	1,209,900,000
Aggregate loss of investments with unrealized losses less than one year	1,400,000	2,200,000
Unrealized Gain (loss) on contracts	$ 2,400,000	$ (2,900,000)	$ 8,000,000
Accounts Receivable | Customer 1 | Minimum
Financial Instruments and Fair Value [Line Items]
Concentration risk, percentage	10.00%
Accounts Receivable | Customer 2 | Minimum
Financial Instruments and Fair Value [Line Items]
Concentration risk, percentage		10.00%
Debt Mutual Funds
Financial Instruments and Fair Value [Line Items]
Available-for-sale marketable securities, Fair Market Value of Investments in debt securities with Unrealized Losses	$ 0
Available for sale securities with out contractual maturity date	3,200,000
Mobile Industrial Robots (MiR)
Financial Instruments and Fair Value [Line Items]
Maximum amount of contingent consideration paid for acquisition	115,000,000
Foreign Exchange Contracts
Financial Instruments and Fair Value [Line Items]
Unrealized Gain (loss) on contracts	$ (400,000)	$ (100,000)

Schedule of Fair Value of Finan

Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	$ 256,636	$ 1,473,905
Contingent consideration	31,000
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	109,721	855,795
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	86,117	282,840
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	40,020	133,186
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	9,611	10,726
Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	7,604	167,342
Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	3,187
Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	376	586
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	1,204,579	1,903,748
Derivative assets	79	389
Total	1,204,658	1,904,137
Contingent consideration	70,543	45,102
Derivative liabilities	514	446
Total	71,057	45,548
Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	312,512	197,955
Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	614,240	231,888
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	109,721	855,795
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	86,117	282,840
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	40,020	133,186
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	9,611	10,726
Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	7,604	167,342
Fair Value, Measurements, Recurring | Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	3,187
Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	376	586
Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	21,191
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	590,415	427,720
Total	590,415	427,720
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	312,512	197,955
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	253,525	206,335
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	3,187
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	21,191
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	614,164	1,476,028
Derivative assets	79	389
Total	614,243	1,476,417
Derivative liabilities	514	446
Total	514	446
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	360,715	25,553
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	109,721	855,795
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	86,117	282,840
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	40,020	133,186
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	9,611	10,726
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	7,604	167,342
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	376	586
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent consideration	70,543	45,102
Total	$ 70,543	$ 45,102

Schedule of Reported Financial

Schedule of Reported Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	$ 1,204,658	$ 1,904,137
Liabilities	71,057	45,548
Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	514	446
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	926,752	429,843
Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	190,096	1,347,979
Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	87,731	125,926
Prepayments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	79	389
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	34,865	24,497
Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	35,678	20,605
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	590,415	427,720
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	566,037	404,290
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	24,378	23,430
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	614,243	1,476,417
Liabilities	514	446
Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	514	446
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	360,715	25,553
Significant Other Observable Inputs (Level 2) | Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	190,096	1,347,979
Significant Other Observable Inputs (Level 2) | Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	63,353	102,496
Significant Other Observable Inputs (Level 2) | Prepayments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	79	389
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	70,543	45,102
Significant Unobservable Inputs (Level 3) | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	34,865	24,497
Significant Unobservable Inputs (Level 3) | Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	$ 35,678	$ 20,605

Schedule of Changes in Fair Val

Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 45,102		$ 38,332
Acquisition of MiR	52,547
Foreign currency impact	(3,540)
Payments	(24,553)	[1]	(1,050)	[2]
Fair value adjustment	987	[3]	7,820	[4]
Balance at end of period	$ 70,543		$ 45,102
[1]	During the year ended December 31, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out in connection with the acquisition of Universal Robots.
[2]	During the year ended December 31, 2017, Teradyne paid $1.1 million of contingent consideration for the earn-out in connection with the acquisition of AIT.
[3]	During the year ended December 31, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of MiR was increased by $17.7 million primarily due to an increase in forecasted revenues. During the year ended December 31, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was decreased by $16.7 million primarily due to a decrease in forecasted revenues.
[4]	During the year ended December 31, 2017, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was increased by $7.8 million primarily due to an increase in forecasted revenues and decrease in discount rate.

Schedule of Changes in Fair V_2

Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration									$ 13,571	$ 1,050	$ 11,697
Increase (decrease) in contingent consideration									987	7,820	15,896
Universal Robots (UR)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration									24,600
Increase (decrease) in contingent consideration	$ 7,400	$ 800	$ 3,500	$ 5,000	$ 6,000	$ (300)	$ 1,500	$ 600	(16,700)	7,800	15,300
Avionics Interface Technologies, LLC
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration										$ 1,100
Increase (decrease) in contingent consideration											$ 600
MiR
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Increase (decrease) in contingent consideration									$ 17,700

Quantitative Information Associ

Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Apr. 25, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration		$ 31,000
Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration			$ 52,600
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Target achievement, volatility		18.00%
Discount Rate		1.10%
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	[1]	$ 66,672
Monte Carlo Simulation | Revenue for the period July 1, 2018-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Universal Robots (UR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	[1]	$ 3,871
[1]	Contingent consideration related to MiR and Universal Robots acquisitions of $31.0 million and $3.9 million, respectively, is expected to be paid in March 2019.

Quantitative Information Asso_2

Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument (Parenthetical) (Detail) - Scenario, Forecast $ in Millions	1 Months Ended
	Mar. 31, 2019USD ($)
Universal Robots (UR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Payment for contingent consideration	$ 3.9
Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Payment for contingent consideration	$ 31

Schedule of Carrying Amounts an

Schedule of Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Marketable securities		$ 256,636	$ 1,473,905
Contingent consideration		31,000
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		926,752	429,843
Marketable securities		277,827	1,473,905
Derivative assets		79	389
Contingent consideration		70,543	45,102
Derivative liabilities		514	446
Convertible debt	[1]	379,981	365,987
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		926,752	429,843
Marketable securities		277,827	1,473,905
Derivative assets		79	389
Contingent consideration		70,543	45,102
Derivative liabilities		514	446
Convertible debt	[1]	$ 547,113	$ 659,525
[1]	The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note which includes the equity conversion features.

Schedule of Available for Sale

Schedule of Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 259,011	$ 1,470,729
Available-for-sale marketable securities, Unrealized Gain	592	6,582
Available-for-sale marketable securities, Unrealized (Loss)	(2,967)	(3,406)
Available-for-sale marketable securities, Fair Market Value	256,636	1,473,905
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	191,978	1,350,896
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	110,969	858,258
Available-for-sale marketable securities, Unrealized Gain	112	72
Available-for-sale marketable securities, Unrealized (Loss)	(1,360)	(2,535)
Available-for-sale marketable securities, Fair Market Value	109,721	855,795
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	75,040	850,163
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	86,130	283,009
Available-for-sale marketable securities, Unrealized Gain	13	18
Available-for-sale marketable securities, Unrealized (Loss)	(26)	(187)
Available-for-sale marketable securities, Fair Market Value	86,117	282,840
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	85,094	258,933
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	41,133	131,179
Available-for-sale marketable securities, Unrealized Gain	432	2,380
Available-for-sale marketable securities, Unrealized (Loss)	(1,545)	(373)
Available-for-sale marketable securities, Fair Market Value	40,020	133,186
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	24,767	91,010
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	9,646	10,775
Available-for-sale marketable securities, Unrealized Gain	1
Available-for-sale marketable securities, Unrealized (Loss)	(36)	(49)
Available-for-sale marketable securities, Fair Market Value	9,611	10,726
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	7,077	10,727
Certificates of Deposit and Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	7,604	167,523
Available-for-sale marketable securities, Unrealized Gain		6
Available-for-sale marketable securities, Unrealized (Loss)		(187)
Available-for-sale marketable securities, Fair Market Value	7,604	167,342
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		138,340
Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	3,153
Available-for-sale marketable securities, Unrealized Gain	34
Available-for-sale marketable securities, Fair Market Value	3,187
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	0
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	376	582
Available-for-sale marketable securities, Unrealized Gain		4
Available-for-sale marketable securities, Fair Market Value	$ 376	586
Equity and Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost		19,403
Available-for-sale marketable securities, Unrealized Gain		4,102
Available-for-sale marketable securities, Unrealized (Loss)		(75)
Available-for-sale marketable securities, Fair Market Value		23,430
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		$ 1,723

Schedule of Reported Available

Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 259,011	$ 1,470,729
Available-for-sale marketable securities, Unrealized Gain	592	6,582
Available-for-sale marketable securities, Unrealized (Loss)	(2,967)	(3,406)
Available-for-sale marketable securities, Fair Market Value	256,636	1,473,905
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	191,978	1,350,896
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	190,100	1,349,970
Available-for-sale marketable securities, Unrealized Gain	88	38
Available-for-sale marketable securities, Unrealized (Loss)	(92)	(2,029)
Available-for-sale marketable securities, Fair Market Value	190,096	1,347,979
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	140,262	1,288,844
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	68,911	120,759
Available-for-sale marketable securities, Unrealized Gain	504	6,544
Available-for-sale marketable securities, Unrealized (Loss)	(2,875)	(1,377)
Available-for-sale marketable securities, Fair Market Value	66,540	125,926
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 51,716	$ 62,052

Contractual Maturities of Inves

Contractual Maturities of Investments in Debt Securities Held (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Schedule of Available-for-sale Securities
Due within one year, cost	$ 190,100
Due after 1 year through 5 years, cost	9,199
Due after 5 years through 10 years, cost	14,081
Due after 10 years, cost	42,478
Total, cost	255,858
Due within one year, fair market value	190,096
Due after 1 year through 5 years, fair market value	9,144
Due after 5 years through 10 years, fair market value	13,405
Due after 10 years, fair maket value	40,804
Total, fair market value	$ 253,449

Schedule of Notional Amount of

Schedule of Notional Amount of Derivatives (Detail) - Foreign Exchange Contracts - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	$ 48.7	$ 5
Buy Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(57.2)	(55.9)
Sell Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	105.9	60.9
Japanese Yen
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(35)	(35.7)
Japanese Yen | Buy Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(35)	(35.7)
Taiwan Dollar
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(11.2)	(9.9)
Taiwan Dollar | Buy Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(11.2)	(9.9)
Korean Won
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(9.6)	(8.9)
Korean Won | Buy Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(9.6)	(8.9)
British Pound Sterling
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(1.4)	(1.4)
British Pound Sterling | Buy Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Liability, Notional amounts	(1.4)	(1.4)
Euro
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	82.2	27.4
Euro | Sell Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	82.2	27.4
Singapore Dollar
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	15.7	33.5
Singapore Dollar | Sell Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	15.7	$ 33.5
Philippines, Pesos
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	5.2
Philippines, Pesos | Sell Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	5.2
China, Yuan Renminbi
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	2.8
China, Yuan Renminbi | Sell Position
Intercompany Foreign Currency Balance [Line Items]
Derivative Asset, Notional amounts	$ 2.8

Schedule of Derivative Instrume

Schedule of Derivative Instruments in Statement of Financial Position at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), net	$ (435)	$ (57)
Not Designated as Hedging Instrument | Foreign currency forward contracts | Prepayments
Derivatives, Fair Value [Line Items]
Derivative assets	79	389
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ (514)	$ (446)

Schedule of Effect of Derivativ

Schedule of Effect of Derivative Instruments in Statement of Operations Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Losses (Gains) on derivatives recognized in statements of operations	$ 7,257	$ (1,133)	$ 8,671

Schedule of Effect of Derivat_2

Schedule of Effect of Derivative Instruments in Statement of Operations Recognized (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on foreign currency transactions	$ 2.4	$ (2.9)	$ 8

Debt - Additional Information (

Debt - Additional Information (Detail) $ / shares in Units, $ in Thousands, shares in Millions	Dec. 12, 2016USD ($)Customershares	Apr. 27, 2015USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)$ / sharesshares
Debt Instrument
Debt instrument, net proceeds after issuance costs					$ 450,800
Repurchase of common stock			$ 823,478	$ 200,304	$ 146,331
Repurchase of stock, shares | shares					6.8
Term of loan, years		5 years
Pledge percentage of capital stock		65.00%
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Aggregate principal amount			$ 460,000	$ 460,000	$ 460,000
Debt instrument, interest rate, stated percentage					1.25%
Debt instrument, net proceeds after issuance costs	$ 450,800
Payment for net cost of convertible note hedges net of warrant proceeds	33,000
Repurchase of common stock	$ 50,100
Repurchase of stock, shares | shares	2
Senior notes maturity date	Dec. 15, 2023
Debt instrument, frequency of periodic payment	payable semiannually in arrears on June 15 and December 15 of each year
Debt instrument, date of first required payment	Jun. 15, 2017
Debt instrument, conversion option expiration date	Sep. 15, 2023
Debt instrument conversion price | $ / shares			$ 31.70		$ 31.70
Shares that would be issued upon conversion | shares			14.5
Strike price per share of warrant | $ / shares			$ 39.78
Debt instrument, convertible, carrying amount of equity component			$ 100,800		$ 100,800
Debt instrument, effective annual interest rate			5.00%
Financing cost			$ 5,300		$ 7,200
Debt issuance costs, amortization period			7 years
Unamortized discount			$ 80,000
Debt Instrument, convertible, remaining discount amortization period			5 years
Value of notes converted			$ 455,400
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option one
Debt Instrument
Trading days measurement period | Customer	20
Consecutive trading days measurement period | Customer	30
Percentage of conversion price	130.00%
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option two
Debt Instrument
Trading days measurement period | Customer	5
Consecutive trading days measurement period | Customer	5
Percentage of closing sale price of common stock and conversion rate product	98.00%
Maximum
Debt Instrument
Aggregate principal amount		$ 150,000
Commitment fee percentage of unused portion of credit facility		0.35%
Minimum
Debt Instrument
Commitment fee percentage of unused portion of credit facility		0.125%
Base Rate | Maximum
Debt Instrument
Debt instrument, basis spread on variable rate		1.00%
Base Rate | Minimum
Debt Instrument
Debt instrument, basis spread on variable rate		0.00%
London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument
Debt instrument, basis spread on variable rate		2.00%
London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument
Debt instrument, basis spread on variable rate		1.00%
Revolving Credit Facility
Debt Instrument
Financing cost			$ 2,300
Financing cost, amortization term			5 years
Revolving Credit Facility | Maximum
Debt Instrument
Credit facility, borrowing capacity		$ 350,000

Components of Convertible Senio

Components of Convertible Senior Notes (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument
Net carrying amount of convertible debt	$ 379,981	$ 365,987
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Debt principal	460,000	460,000	$ 460,000
Unamortized discount	80,019	94,013
Net carrying amount of convertible debt	$ 379,981	$ 365,987

Interest Expense on Convertible

Interest Expense on Convertible Senior Notes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument
Contractual interest expense on the coupon	$ 5,750	$ 5,734
Amortization of the discount component and debt issue fees recognized as interest expense	13,995	13,318
Total interest expense on the convertible debt	$ 19,745	$ 19,052

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		$ 1,953,646	$ 1,828,659	$ 1,965,786
Other comprehensive income (loss) before reclassifications, net of tax		(30,552)	39,703
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		0	(713)
Other comprehensive (loss) income		(29,460)	38,990	(12,070)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax	[1]	769
Reclassification of unrealized gains on equity securities, net of tax		1,337	(441)	(683)
Balance		1,522,354	1,953,646	1,828,659
ASU 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax	[2]	(3,125)
Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		15,919	(21,921)
Other comprehensive income (loss) before reclassifications, net of tax		(28,442)	37,840
Other comprehensive (loss) income		(28,442)	37,840
Balance		(12,523)	15,919	(21,921)
Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		1,362	(60)
Other comprehensive income (loss) before reclassifications, net of tax		(2,110)	1,863
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		1,337	(441)
Other comprehensive (loss) income		(773)	1,422
Reclassification of tax effects resulting from the Tax Reform Act, net of tax	[1]	691
Balance		(1,845)	1,362	(60)
Unrealized Gains (Losses) on Marketable Securities | ASU 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax	[2]	(3,125)
Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		1,495	1,767
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		(245)	(272)	(321)
Other comprehensive (loss) income		(245)	(272)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax	[1]	78
Balance		1,328	1,495	1,767
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		18,776	(20,214)	(8,144)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		(769)	(713)	(1,004)
Reclassification of unrealized gains on equity securities, net of tax		1,337	(441)	(683)
Balance		$ (13,040)	$ 18,776	$ (20,214)
[1]	In the year ended December 31, 2018, Teradyne early adopted ASU 2018-02, “Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” As a result, the stranded tax effects resulting from the Tax Reform Act enacted in December 2017 were reclassified from accumulated other comprehensive income to retained earnings.
[2]	In the year ended December 31, 2018, Teradyne adopted ASU 2016-01, “Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities.” See Note B: “Accounting Policies.”

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss), tax	$ (92)	$ (451)	$ (445)
Reclassification of income tax effects from the Tax Reform Act, net of tax	769
Reclassification of unrealized gains on equity securities, net of tax	21	297	255
Foreign currency translation adjustments, tax	0	0	0
Unrealized (losses) gains on marketable securities, tax	(521)	1,815	209
Retirement plans prior service benefit, tax	(1,081)	(932)	(778)
Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax	0	0
Amounts reclassified from accumulated other comprehensive income (loss), tax	0	0
Other comprehensive income (loss), tax	0	0
Reclassification of income tax effects from the Tax Reform Act, net of tax	0
Unrealized (Losses) Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax	(722)	1,903
Amounts reclassified from accumulated other comprehensive income (loss), tax	(21)	(297)	(255)
Other comprehensive income (loss), tax	(743)	1,606
Reclassification of income tax effects from the Tax Reform Act, net of tax	(691)
Reclassification of unrealized gains on equity securities, net of tax	902
Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax	0	0
Amounts reclassified from accumulated other comprehensive income (loss), tax	(71)	(154)	$ (190)
Other comprehensive income (loss), tax	(71)	$ (154)
Reclassification of income tax effects from the Tax Reform Act, net of tax	(78)
ASU 2016-01 | Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax	0
ASU 2016-01 | Unrealized (Losses) Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax	(902)
ASU 2016-01 | Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax	$ 0

Reclassifications Out of Accumu

Reclassifications Out of Accumulated Other Comprehensive Income to Statements of Operations (Detail) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

[1],[2]

Sep. 30, 2018

[2],[3]

Jul. 01, 2018

[2],[4]

Apr. 01, 2018

[5]

Dec. 31, 2017

[6],[7]

Oct. 01, 2017

[7],[8]

Jul. 02, 2017

[7],[9]

Apr. 02, 2017

[10]

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

Interest income and interest expense

$ (9,083)

$ (6,213)

$ (5,427)

$ (5,981)

$ (6,476)

$ (4,517)

$ (3,292)

$ (3,520)

$ (26,704)

$ (17,805)

$ (9,296)

Reclassifications, net of tax

0

713

Unrealized (Losses) Gains on Marketable Securities

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

Reclassifications, net of tax

(1,337)

441

Amortization of Prior Service Credit

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

Reclassifications, net of tax

245

272

321

Accumulated Other Comprehensive Income (Loss)

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

Reclassifications, net of tax

769

713

1,004

Reclassification out of Accumulated Other Comprehensive Income | Unrealized (Losses) Gains on Marketable Securities

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

Interest income and interest expense

$ (1,337)

$ 441

$ 683

[1]

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.

[2]

Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[3]

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.

[4]

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.

[5]

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.

[6]

Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.

[7]

Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[8]

Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.

[9]

Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.

[10]

Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Reclassifications Out of Accu_2

Reclassifications Out of Accumulated Other Comprehensive Income to Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 92	$ 451	$ 445
Unrealized (Losses) Gains on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	21	297	255
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 71	$ 154	$ 190

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

[2],[3]

Jul. 01, 2018

[2],[4]

Apr. 01, 2018

[5]

Dec. 31, 2017

Oct. 01, 2017

[7],[8]

Jul. 02, 2017

[7],[9]

Apr. 02, 2017

[10]

Jul. 03, 2016

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Line Items]

Goodwill

$ 381,850

$ 252,011

$ 381,850

$ 252,011

$ 223,343

Goodwill impairment

254,946

Acquired intangible assets impairment

8,800

83,339

Intangible assets remaining balance

125,482

79,088

125,482

79,088

Acquired intangible assets amortization

10,558

[1],[2]

$ 11,142

$ 9,793

$ 7,698

7,384

[6],[7]

$ 7,028

$ 8,166

$ 7,952

39,191

30,530

52,648

Wireless Test

Goodwill and Intangible Assets Disclosure [Line Items]

Employee reduction, percentage

11.00%

Goodwill

7,976

$ 7,976

$ 8,000

7,976

$ 7,976

7,976

Goodwill impairment

254,900

254,946

Acquired intangible assets impairment

$ 83,300

$ 83,339

Intangible assets remaining balance

$ 2,200

$ 2,200

Wireless Test | Sales Revenue, Segment | Customer Concentration Risk | Minimum

Goodwill and Intangible Assets Disclosure [Line Items]

Concentration risk, percentage

51.00%

Wireless Test | Sales Revenue, Segment | Customer Concentration Risk | Maximum

Goodwill and Intangible Assets Disclosure [Line Items]

Concentration risk, percentage

73.00%

[1]

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.

[2]

Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[3]

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.

[4]

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.

[5]

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.

[6]

Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.

[7]

Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[8]

Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.

[9]

Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.

[10]

Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Changes in Carrying Amount of G

Changes in Carrying Amount of Goodwill by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 03, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Apr. 25, 2018	Feb. 26, 2018
Goodwill [Line Items]
Foreign currency translation adjustment		$ (20,531)	$ 28,668
Goodwill impairment losses			(254,946)
Goodwill		1,014,577	985,909	$ 1,144,416
Accumulated impairment losses		(762,566)	(762,566)	(762,566)
Goodwill		252,011	223,343	381,850
Mobile Industrial Robots (MiR)
Goodwill [Line Items]
Goodwill acquisition		135,976
Goodwill					$ 135,976
Energid Technologies Corporation
Goodwill [Line Items]
Goodwill acquisition		14,394
Goodwill						$ 14,400
Industrial Automation
Goodwill [Line Items]
Foreign currency translation adjustment		(20,531)	28,668
Goodwill		233,519	204,851	363,358
Goodwill		233,519	204,851	363,358
Industrial Automation | Mobile Industrial Robots (MiR)
Goodwill [Line Items]
Goodwill acquisition		135,976
Industrial Automation | Energid Technologies Corporation
Goodwill [Line Items]
Goodwill acquisition		14,394
Wireless Test
Goodwill [Line Items]
Goodwill impairment losses	$ (254,900)		(254,946)
Goodwill		361,819	361,819	361,819
Accumulated impairment losses		(353,843)	(353,843)	(353,843)
Goodwill	$ 8,000	7,976	7,976	7,976
Semiconductor Test
Goodwill [Line Items]
Goodwill		260,540	260,540	260,540
Accumulated impairment losses		(260,540)	(260,540)	(260,540)
Goodwill		0	0	0
System Test
Goodwill [Line Items]
Goodwill		158,699	158,699	158,699
Accumulated impairment losses		(148,183)	(148,183)	(148,183)
Goodwill		$ 10,516	$ 10,516	$ 10,516

Schedule of Amortizable Intangi

Schedule of Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 498,231	$ 414,038
Accumulated Amortization	(367,531)	(337,155)
Foreign Currency Translation Adjustment	(5,218)	2,205
Net Carrying Amount	125,482	79,088
Developed technology
Finite-Lived Intangible Assets
Gross Carrying Amount	336,308	270,877
Accumulated Amortization	(252,080)	(226,190)
Foreign Currency Translation Adjustment	(4,079)	1,618
Net Carrying Amount	80,149	46,305
Customer Relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	97,153	92,741
Accumulated Amortization	(83,448)	(83,585)
Foreign Currency Translation Adjustment	(340)	171
Net Carrying Amount	13,365	9,327
Trademarks and tradenames
Finite-Lived Intangible Assets
Gross Carrying Amount	64,420	50,100
Accumulated Amortization	(31,653)	(27,120)
Foreign Currency Translation Adjustment	(799)	416
Net Carrying Amount	31,968	23,396
Non-compete Agreements
Finite-Lived Intangible Assets
Gross Carrying Amount	320	320
Accumulated Amortization	(320)	(260)
Net Carrying Amount		$ 60
Backlog [Member]
Finite-Lived Intangible Assets
Gross Carrying Amount	30
Accumulated Amortization	$ (30)

Schedule of Amortizable Intan_2

Schedule of Amortizable Intangible Assets (Parenthetical) (Detail) - USD ($) $ in Thousands	Apr. 25, 2018	Dec. 31, 2018	Dec. 31, 2016
Finite-Lived Intangible Assets
Impairment of intangible assets		$ 8,800	$ 83,339
Intangible Assets [Member]
Finite-Lived Intangible Assets
Impairment of intangible assets		8,800
Mobile Industrial Robots (MiR)
Finite-Lived Intangible Assets
Intangible assets acquired	$ 80,670	80,700
Energid Technologies Corporation
Finite-Lived Intangible Assets
Intangible assets acquired		$ 12,300

Schedule of Estimated Intangibl

Schedule of Estimated Intangible Asset Amortization Expense (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Finite-Lived Intangible Assets
2,019	$ 38,496
2,020	24,186
2,021	13,945
2,022	13,052
2,023	12,785
Thereafter	$ 23,018

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Purchase Commitment, Excluding Long-term Commitment
Aggregate purchase commitments	$ 242.1
Purchase commitments less than one year	232.5
Rental expense under lease commitments	$ 19.3	$ 20.2	$ 19.1
Warranty period	1 year
Product warranty accrual	$ 7.9	8.2
Revenue deferrals related to extended warranties	$ 27.4	$ 24.4

Non Cancelable Operating Lease

Non Cancelable Operating Lease Commitments (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Line Items]
2,019	$ 19,570
2,020	18,293
2,021	13,578
2,022	9,693
2,023	5,449
Beyond 2,024	9,472
Total	$ 76,055

Computation of Basic and Dilute

Computation of Basic and Diluted Net (Loss) Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2018	[1],[2]	Sep. 30, 2018	[2],[3]	Jul. 01, 2018	[2],[4]	Apr. 01, 2018	[5]	Dec. 31, 2017	[6],[7]	Oct. 01, 2017	[7],[8]	Jul. 02, 2017	[7],[9]	Apr. 02, 2017	[10]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Income Loss Per Common Share
Net income (loss) for basic and diluted net income per share		$ 143,790		$ 119,978		$ 101,037		$ 86,974		$ (105,923)		$ 103,420		$ 174,976		$ 85,221		$ 451,779	$ 257,692	$ (43,421)
Weighted average common shares-basic																		187,672	198,069	202,578
Incremental shares from assumed conversion of convertible notes	[11]																	2,749	1,298
Convertible note hedge warrant shares	[12]																	485	112
Employee stock purchase rights																		36	27	0
Dilutive potential common shares																		4,933	3,572
Weighted average common shares-diluted																		192,605	201,641	202,578
Net income (loss) per common share-basic		$ 0.80		$ 0.65		$ 0.53		$ 0.45		$ (0.54)		$ 0.52		$ 0.88		$ 0.43		$ 2.41	$ 1.30	$ (0.21)
Net income (loss) per common share-diluted		$ 0.79		$ 0.63		$ 0.52		$ 0.43		$ (0.54)		$ 0.52		$ 0.87		$ 0.42		$ 2.35	$ 1.28	$ (0.21)
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements																		1,385	1,800
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements																		278	335	0
[1]	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.
[2]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[3]	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.
[4]	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.
[5]	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.
[6]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[7]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[8]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[9]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[10]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.
[11]	Incremental shares from the assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.70, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period.
[12]	Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.78, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period.

Computation of Basic and Dilu_2

Computation of Basic and Diluted Net (Loss) Income Per Common Share (Parenthetical) (Detail) shares in Millions	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Convertible Notes
Net Income Loss Per Common Share
Initial debt conversion price | $ / shares	$ 31.70
Shares that would be issued upon conversion | shares	14.5
Convertible Notes Hedge Warrant
Net Income Loss Per Common Share
Initial debt conversion price | $ / shares	$ 39.78
Shares that would be issued upon conversion | shares	14.5

Net (Loss) Income Per Common Sh

Net (Loss) Income Per Common Share - Additional Information (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Net Income Loss Per Common Share
Exercise of stock options	0.1	0.1
Restricted Stock Units (RSUs) [Member]
Net Income Loss Per Common Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.5

Restructuring and Other - Addit

Restructuring and Other - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve
Contingent consideration adjustment									$ 987	$ 7,820	$ 15,896
Severance benefit and charges	$ 800	$ 1,700	$ 2,400	$ 3,900	$ 1,800	$ 600	$ 800	$ 600
Acquisition related costs	500	800	2,500	800					4,500
Lease termination period										2017-09
Property, Plant and Equipment
Restructuring Cost and Reserve
Impairment of fixed assets and other expenses											4,200
Wireless Test
Restructuring Cost and Reserve
Lease impairment										$ 1,000
Semiconductor Test | Property, Plant and Equipment
Restructuring Cost and Reserve
Impairment of fixed assets and other expenses										1,100
Impairment of Fixed Assets and Expenses Related to the Japan Earthquake
Restructuring Cost and Reserve
Property insurance, recovery						5,100				5,100	5,100
Impairment of Fixed Assets and Expenses Related to the Japan Earthquake | Earthquake Related Expenses
Restructuring Cost and Reserve
Impairment of fixed assets and other expenses						800				800	900
Universal Robots (UR)
Restructuring Cost and Reserve
Contingent consideration adjustment	7,400	$ 800	$ 3,500	$ 5,000	$ 6,000	$ (300)	$ 1,500	$ 600	(16,700)	7,800	15,300
Avionics Interface Technologies, LLC
Restructuring Cost and Reserve
Contingent consideration adjustment											600
Mobile Industrial Robots (MiR)
Restructuring Cost and Reserve
Contingent consideration adjustment	$ 17,700								17,700
Semiconductor Test and Wireless Test
Restructuring Cost and Reserve
Severance benefit and charges											$ 6,000
System Test and Semiconductor Test
Restructuring Cost and Reserve
Severance benefit and charges									$ 8,700
Semiconductor Test, Industrial Automation and Corporate
Restructuring Cost and Reserve
Severance benefit and charges										$ 3,800

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)Participant	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Defined Benefit Plan Disclosure
Number of retiree participants | Participant	1,700
Defined Benefit Plan, decrease in benefit obligation	$ (151,300)
Defined Benefit Plan, decrease in plan assets	(151,300)
Gain (Loss) Due to Settlement	(300)
Fair value of pension plans assets totaled	145,700
Transfer out of level 3	$ 2,700
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Discount rate utilized to determine future pension obligations	4.00%	3.40%	3.90%
Fair value of pension plans assets totaled
Contribution to defined benefit pension plans	889	$ 557
Accumulated other comprehensive income (loss), prior service cost expected to be recognized in 2018	$ (200)
United States Plans
Defined Benefit Plan Disclosure
Percentage of expected return on plan assets assumption	4.25%
Discount rate utilized to determine future pension obligations	4.15%	3.40%
Fair value of pension plans assets totaled	$ 144,300
Contribution to defined benefit pension plans	2,600	$ 1,900
U.S. Supplemental Executive Defined Benefit Pension Plan
Defined Benefit Plan Disclosure
Contribution to defined benefit pension plans	800	2,600
Contribution to defined benefit pension plans in 2018	2,700
Non-United States Subsidiaries
Defined Benefit Plan Disclosure
Contribution to defined benefit pension plans	900	900
Contribution to defined benefit pension plans in 2018	900
Taiwan Defined Benefit Pension Plan
Defined Benefit Plan Disclosure
Fair value of pension plans assets totaled	1,400
UNITED STATES
Defined Benefit Plan Disclosure
Accumulated benefit obligation for defined benefit pension plans	$ 172,800	$ 354,300
Percentage of expected return on plan assets assumption	4.30%	4.00%	4.80%
Discount rate utilized to determine future pension obligations	4.10%	3.40%
Fair value of pension plans assets totaled	$ 144,301	$ 324,506	$ 307,304
Contribution to defined benefit pension plans	2,587	4,462
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Accumulated benefit obligation for defined benefit pension plans	$ 35,600	$ 34,700
Percentage of expected return on plan assets assumption	1.50%	2.00%	2.00%
Discount rate utilized to determine future pension obligations	1.80%	1.80%
Fair value of pension plans assets totaled	$ 1,400	$ 1,307	$ 27,571
Contribution to defined benefit pension plans	$ 822	$ 883

Schedule of Defined Benefit Pen

Schedule of Defined Benefit Pension and Postretirement Benefit Plan Assets and Obligation (Detail) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Dec. 31, 2017	Jul. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Actuarial (gain) loss	$ (3,500)	$ 300	$ (100)	$ (3,800)	$ (2,800)
Ending Balance	145,700					$ 145,700
UNITED STATES
Defined Benefit Plan Disclosure
Projected benefit obligation, Beginning of year						363,026	$ 353,616
Service cost						2,196	2,239	$ 2,302
Interest cost						8,940	13,151	13,630
Actuarial (gain) loss						(30,136)	12,702
Benefits paid						(14,793)	(18,682)
Retiree annuity purchase						(151,341)
Liability loss due to settlement						345
Projected benefit obligation, End of year	178,237			363,026		178,237	363,026	353,616
Beginning Balance						324,506	307,304
Company contributions						2,587	4,462
Actual return on plan assets						(16,658)	31,422
Benefits paid						(14,793)	(18,682)
Retiree annuity purchase						(151,341)
Ending Balance	144,301			324,506		144,301	324,506	307,304
Funded status	(33,936)			(38,520)		(33,936)	(38,520)
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Projected benefit obligation, Beginning of year						39,353	60,738
Service cost						786	818	761
Interest cost						687	852	1,185
Actuarial (gain) loss						773	262
Benefits paid						(741)	(994)
Settlements							(28,560)
Admin expenses paid							(40)
Non-U.S. currency movement						(1,712)	6,277
Projected benefit obligation, End of year	39,146			39,353		39,146	39,353	60,738
Beginning Balance						1,307	27,571
Company contributions						822	883
Actual return on plan assets						50	737
Benefits paid						(741)	(994)
Settlements							(28,560)
Admin expenses paid							(40)
Non-U.S. currency movement						(38)	1,710
Ending Balance	1,400			1,307		1,400	1,307	27,571
Funded status	(37,746)			(38,046)		(37,746)	(38,046)
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Projected benefit obligation, Beginning of year						6,177	5,510
Service cost						39	34	37
Interest cost						196	201	218
Actuarial (gain) loss						25	398
Special termination benefits						3,708	591
Benefits paid						(889)	(557)
Projected benefit obligation, End of year	9,256			6,177		9,256	6,177	$ 5,510
Beginning Balance
Company contributions						889	557
Benefits paid						(889)	(557)
Ending Balance
Funded status	$ (9,256)			$ (6,177)		$ (9,256)	$ (6,177)

Schedule of Amounts Recorded wi

Schedule of Amounts Recorded within Statements of Financial Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure
Retirement plans assets	$ 16,883	$ 17,491
UNITED STATES
Defined Benefit Plan Disclosure
Retirement plans assets	16,883	17,491
Accrued employees' compensation and withholdings	(2,676)	(2,524)
Retirement plans liabilities	(48,143)	(53,487)
Funded status	(33,936)	(38,520)
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Accrued employees' compensation and withholdings	(852)	(863)
Retirement plans liabilities	(36,894)	(37,183)
Funded status	(37,746)	(38,046)
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Accrued employees' compensation and withholdings	(1,310)	(591)
Retirement plans liabilities	(7,946)	(5,586)
Funded status	$ (9,256)	$ (6,177)

Schedule of Amounts Recognized

Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Deferred taxes	$ (20,025)	$ (12,881)	$ (9,398)
Total recognized in other comprehensive income, net of tax
UNITED STATES
Defined Benefit Plan Disclosure
Prior service cost, before tax		58
Deferred taxes	560	539
Total recognized in other comprehensive income, net of tax	560	597
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Prior service cost, before tax
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Prior service cost, before tax	(249)	(622)
Deferred taxes	(1,641)	(1,472)
Total recognized in other comprehensive income, net of tax	$ (1,890)	$ (2,094)

Schedule of Pension Plans with

Schedule of Pension Plans with Accumulated Benefit Obligation and Projected Benefit Obligation in Excess of Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure
Fair value of plan assets
UNITED STATES
Defined Benefit Plan Disclosure
Projected benefit obligation	50.8	$ 56
Accumulated benefit obligation	48.6	51.6
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Projected benefit obligation	39.1	39.4
Accumulated benefit obligation	35.6	34.7
Fair value of plan assets	$ 1.4	$ 1.3

Schedule of Net Periodic Pensio

Schedule of Net Periodic Pension and Postretirement (income) Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Net actuarial (gain) loss	$ (3,316)	$ (6,624)	$ (3,203)
UNITED STATES
Defined Benefit Plan Disclosure
Service cost	2,196	2,239	2,302
Interest cost	8,940	13,151	13,630
Expected return on plan assets	(9,049)	(12,008)	(13,830)
Amortization of prior service cost	58	70	96
Net actuarial (gain) loss	(4,429)	(6,712)	(4,013)
Settlement loss	345
Total net periodic pension (income) cost	(1,939)	(3,260)	(1,815)
Prior service cost	(58)	(70)	(96)
Total recognized in other comprehensive income	(58)	(70)	(96)
Total recognized in net periodic postretirement benefit cost (income) and other comprehensive income	(1,997)	(3,330)	(1,911)
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Service cost	786	818	761
Interest cost	687	852	1,185
Expected return on plan assets	(19)	(165)	(443)
Amortization of prior service cost
Net actuarial (gain) loss	743	(310)	815
Settlement loss
Total net periodic pension (income) cost	2,197	1,195	2,318
Prior service cost
Total recognized in other comprehensive income
Total recognized in net periodic postretirement benefit cost (income) and other comprehensive income	2,197	1,195	2,318
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Service cost	39	34	37
Interest cost	196	201	218
Amortization of prior service cost	(373)	(496)	(607)
Net actuarial (gain) loss	25	398	5
Special termination benefits	3,708	591
Total net periodic pension (income) cost	3,595	728	(347)
Prior service cost			(93)
Prior service credit	373	496	607
Total recognized in other comprehensive income	373	496	514
Total recognized in net periodic postretirement benefit cost (income) and other comprehensive income	$ 3,968	$ 1,224	$ 167

Schedule of Weighted Average -

Schedule of Weighted Average - Assumptions to Determine Net Periodic Pension Cost (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
UNITED STATES
Defined Benefit Plan Disclosure
Discount rate	3.40%	3.90%	4.00%
Expected return on plan assets	4.30%	4.00%	4.80%
Salary progression rate	2.30%	2.60%	2.70%
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Discount rate	1.80%	1.80%	2.30%
Expected return on plan assets	1.50%	2.00%	2.00%
Salary progression rate	2.70%	2.70%	3.20%
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Discount rate	3.40%	3.90%	3.90%
Initial health care cost trend rate	7.90%	7.30%	7.50%
Ultimate health care cost trend rate	4.50%	4.50%	5.00%
Year in which ultimate health care cost trend rate is reached	2,026	2,023	2,023

Schedule of Weighted Average As

Schedule of Weighted Average Assumptions to Determine Pension Obligations (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Discount rate	4.00%	3.40%	3.90%
Initial medical trend	7.50%	7.90%	7.30%
Ultimate health care trend	4.50%	4.50%	5.00%
Medical cost trend rate decrease to ultimate rate in year	2,026	2,026	2,023
UNITED STATES
Defined Benefit Plan Disclosure
Discount rate	4.10%	3.40%
Salary progression rate	2.30%	2.30%
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Discount rate	1.80%	1.80%
Salary progression rate	2.60%	2.70%

Schedule of Weighted Average Pe

Schedule of Weighted Average Pension Assets Allocations by Category (Detail)	Dec. 31, 2018	Dec. 31, 2017
UNITED STATES
Defined Benefit Plan Disclosure
Total	100.00%	100.00%
UNITED STATES | Fixed income securities
Defined Benefit Plan Disclosure
Total	94.00%	88.10%
UNITED STATES | Equity securities
Defined Benefit Plan Disclosure
Total	5.00%	9.90%
UNITED STATES | Other than Securities Investment
Defined Benefit Plan Disclosure
Total	1.00%	2.00%
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Total	100.00%	100.00%
Foreign Pension Plans, Defined Benefit | Fixed income securities
Defined Benefit Plan Disclosure
Total
Foreign Pension Plans, Defined Benefit | Equity securities
Defined Benefit Plan Disclosure
Total
Foreign Pension Plans, Defined Benefit | Other than Securities Investment
Defined Benefit Plan Disclosure
Total	100.00%	100.00%

Schedule of Target Assets Alloc

Schedule of Target Assets Allocation (Detail)	Dec. 31, 2018
Barclays Corporate or Better Index | U.S. corporate fixed income
Defined Benefit Plan Disclosure
Target assets allocation percentage	75.00%
MSCI World Minimum Volatility Index | Global equity Securities
Defined Benefit Plan Disclosure
Target assets allocation percentage	5.00%
Barclays Year Treasury Strips Index | U.S. government fixed income
Defined Benefit Plan Disclosure
Target assets allocation percentage	14.00%
Barclays Corporate High Yield Issuer Cap Index | High yield fixed income
Defined Benefit Plan Disclosure
Target assets allocation percentage	5.00%
Citi Group Three Month Treasury Bill Index | Cash
Defined Benefit Plan Disclosure
Target assets allocation percentage	1.00%

Schedule of Fair Value of Pensi

Schedule of Fair Value of Pensions Plan Assets by Asset Category (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Total	$ 145,700
Group Annuity Insurance Contracts | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Total		$ 3,166	$ 29,456
UNITED STATES
Defined Benefit Plan Disclosure
Total	144,301	324,506	307,304
UNITED STATES | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Defined Benefit Plan Disclosure
Total	1,449	3,217
UNITED STATES | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Total	142,852	318,123
UNITED STATES | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Total		3,166
UNITED STATES | Corporate Debt Securities
Defined Benefit Plan Disclosure
Total	115,424	260,294
UNITED STATES | Corporate Debt Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Total	115,424	260,294
UNITED STATES | US Government Debt Securities
Defined Benefit Plan Disclosure
Total	20,176	25,709
UNITED STATES | US Government Debt Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Total	20,176	25,709
UNITED STATES | Global equity Securities
Defined Benefit Plan Disclosure
Total	7,252	32,120
UNITED STATES | Global equity Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Total	7,252	32,120
UNITED STATES | Cash and Cash Equivalents
Defined Benefit Plan Disclosure
Total	1,449	3,217
UNITED STATES | Cash and Cash Equivalents | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Defined Benefit Plan Disclosure
Total	1,449	3,217
UNITED STATES | Group Annuity Insurance Contracts
Defined Benefit Plan Disclosure
Total		3,166
UNITED STATES | Group Annuity Insurance Contracts | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Total		3,166
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Total	1,400	1,307	$ 27,571
Foreign Pension Plans, Defined Benefit | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Total	1,400	1,307
Foreign Pension Plans, Defined Benefit | Other
Defined Benefit Plan Disclosure
Total	1,400	1,307
Foreign Pension Plans, Defined Benefit | Other | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Total	$ 1,400	$ 1,307

Schedule of Defined Benefit Pla

Schedule of Defined Benefit Plans Disclosures (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure
Transfer out of Level 3	$ 2,700
Ending Balance	145,700
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Settlements		$ (28,560)
Interest and market value adjustments	59	959
Benefits paid	(40)	(244)
Other	(15)	(61)
Significant Unobservable Inputs (Level 3) | Group Annuity Insurance Contracts
Defined Benefit Plan Disclosure
Beginning Balance	3,166	29,456
Transfer out of Level 3	(2,658)
Purchases of retiree annuity insurance contracts	(512)
Non-U.S. currency movement		1,616
Ending Balance		$ 3,166

Schedule of Expected Future Ben

Schedule of Expected Future Benefit Payments (Detail) $ in Thousands	Dec. 31, 2018USD ($)
UNITED STATES
Defined Benefit Plan Disclosure
2,019	$ 6,903
2,020	7,133
2,021	8,026
2,022	8,863
2,023	9,584
2024-2028	57,120
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
2,019	874
2,020	1,522
2,021	905
2,022	888
2,023	1,199
2024-2028	5,921
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
2,019	1,310
2,020	1,234
2,021	1,181
2,022	984
2,023	811
2024-2028	$ 2,364

Schedule of One Percent Point C

Schedule of One Percent Point Change in assumed Health Care Cost Trends Rate (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Defined Benefit Plan Disclosure
Effect of one percentage point increase on total service and interest cost components	$ 7
Effect of one percentage point increase on postretirement benefit obligations	181
Effect of one percentage point decrease on total service and interest cost components	(7)
Effect of one percentage point decrease on postretirement benefit obligations	$ (171)

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended						12 Months Ended
	Jan. 31, 2019	Jul. 31, 2018	Jan. 31, 2018	Jul. 31, 2017	Jan. 31, 2017	Jul. 31, 2016	Dec. 31, 2018	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							790,000		939,000	1,471,000
Weighted average grant date fair value of restricted stock units granted							$ 45.99		$ 28.91	$ 18.95
Tax benefit from compensation expense							$ 12,036,000		$ 10,462,000	$ 8,752,000
Total unrecognized expense related to non-vested restricted stock unit awards and stock options							$ 44,000,000
Unrecognized expense related to non-vested restricted stock unit awards and stock options expected to be recognized over weighted average period, in years							2 years 4 months 24 days
Maximum percent of shares allowed to purchase							10.00%
Fair market value							$ 25,000
Maximum number of shares allowed to purchase							6,000
Percentage of common stock price paid							85.00%
Common stock issued to employees		300,000	300,000	300,000	400,000	500,000
Value of common stock issued to employees per share		$ 32.36	$ 35.59	$ 25.53	$ 21.59	$ 16.74		$ 35.59
Number of shares available for grant							7,874,000		8,605,000	9,546,000	10,914,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Cash received from employees, employee stock options exercises							$ 1,000,000		$ 6,800,000	$ 2,900,000
Tax benefit from compensation expense							$ 400,000		$ 2,500,000	$ 800,000
Percentage of common stock price paid							100.00%
Stock Options | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments							4 years
Stock Options | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments							7 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							790,000		939,000	1,471,000
Restricted Stock Units | Employees
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments							4 years
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period							3 years
Share-based compensation arrangement by share-based payment award, description							Capped at four times the grant date value
Minimum age of retirement to be eligible for PRSUs							60 years
Minimum years of service for retirement to be eligible for PRSUs							10 years
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 54.85		$ 35.66	$ 20.29
Stock price							47.70		28.56	19.43
TSR Performance-Based Restricted Stock Units | Measurement Input, Expected Dividend Payment [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Estimated annual dividend amount per share							$ 0.36		$ 0.28	$ 0.24
TSR Performance-Based Restricted Stock Units | Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved								200.00%
TSR Performance-Based Restricted Stock Units | Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved								0.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant							2,500,000
PBIT Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period							3 years
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 46.62		$ 27.72	$ 18.71
Service-Based Restricted Stock Units | Employees
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							600,000		800,000	1,200,000
Weighted average grant date fair value of restricted stock units granted							$ 45.92		$ 28.19	$ 18.88
Service-Based Restricted Stock Units | Non Employee Directors And Certain Employees
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 35.81		$ 34.48	$ 18.71
Service-Based Restricted Stock Units | Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 12.17		$ 7.13	$ 5.30
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Common stock issued to employees	400,000
Value of common stock issued to employees per share	$ 26.67

Schedule of Estimated Fair Valu

Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions (Detail) - TSR Performance-Based Restricted Stock Units	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Risk-free interest rate	2.20%	1.50%	1.00%
Expected historical volatility	26.80%	26.60%	27.00%
Dividend yield	0.80%	1.00%	1.20%
New York Stock Exchange Composite Index
Share-based Compensation Arrangement by Share-based Payment Award
Expected historical volatility	12.40%	13.40%	13.10%

Schedule of Estimated Fair Va_2

Schedule of Estimated Fair Value of Stock Options Grant Using Black Scholes Option Pricing Model (Detail) - Stock Options	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Expected life (years)	5 years	5 years	5 years
Risk-free interest rate	2.40%	2.00%	1.40%
Volatility-historical	26.40%	27.80%	32.90%
Dividend yield	0.80%	1.00%	1.20%

Schedule of Stock Compensation

Schedule of Stock Compensation Plan Activity (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Awarded	790	939	1,471
Forfeited	(128)	(109)	(233)
Outstanding at January 1	531	926	1,121
Granted	69	111	130
Exercised	(94)	(501)	(324)
Expired	0	(5)	(2)
Outstanding at December 31	506	531	926
Vested and expected to vest at December 31	506	531	926
Exercisable at December 31	256	233	598
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Non-vested at January 1	3,174	3,778	4,070
Awarded	790	939	1,471
Vested	(1,382)	(1,434)	(1,530)
Forfeited	(128)	(109)	(233)
Non-vested at December 31	2,454	3,174	3,778

Schedule of Share Based Compens

Schedule of Share Based Compensation Total Shares Available (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Available for grant at January 1	8,605	9,546	10,914
Options granted	(69)	(111)	(130)
Restricted stock units awarded	(790)	(939)	(1,471)
Restricted stock units forfeited	128	109	233
Available for grant at December 31	7,874	8,605	9,546

Schedule of Weighted-Average Re

Schedule of Weighted-Average Restricted Stock Unit Award Fair Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Non-vested at January 1	$ 21.71	$ 18.27	$ 17.66
Awarded	45.99	28.91	18.95
Vested	20.20	17.90	17.36
Forfeited	24.67	20.35	17.80
Non-vested at December 31	$ 29.22	$ 21.71	$ 18.27

Schedule of Restricted Stock Un

Schedule of Restricted Stock Unit Awards Aggregate Intrinsic Value (Detail) - Restricted Stock Units - USD ($) $ / shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Vested	$ 63,688	$ 40,649	$ 30,008
Outstanding	$ 77,015	$ 132,875	$ 95,952
Expected to vest	$ 77,187	$ 130,594	$ 91,871

Schedule of Restricted Stock _2

Schedule of Restricted Stock Units Weighted Average Remaining Contractual Terms (Detail) - Restricted Stock Units	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Outstanding	11 months 1 day	1 year	1 year 14 days
Expected to vest	10 months 28 days	11 months 26 days	1 year 11 days

Schedule of Weighted Average St

Schedule of Weighted Average Stock Options Exercise Price (Detail)	12 Months Ended
	Dec. 31, 2018$ / shares
Share-based Compensation Arrangement by Share-based Payment Award
Outstanding at January 1	$ 13.92
Options granted	47.70
Options exercised	10.89
Outstanding at December 31	19.06
Exercisable at December 31	$ 8.31

Schedule of Stock Option Aggreg

Schedule of Stock Option Aggregated Intrinsic Value Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Exercised	$ 2,960	$ 8,035	$ 3,729
Outstanding	7,359	14,831	12,468
Vested and expected to vest	7,359	14,831	12,468
Exercisable	$ 5,905	$ 9,076	$ 10,217

Schedule of Stock Options Weigh

Schedule of Stock Options Weighted Average Remaining Contractual Terms (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Outstanding	3 years 7 months 6 days	4 years 1 month 6 days	3 years 10 months 24 days
Vested and expected to vest	3 years 7 months 6 days	4 years 1 month 6 days	3 years 10 months 24 days
Exercisable	2 years 4 months 24 days	2 years 9 months 18 days	3 years 2 months 12 days

Schedule of Significant Option

Schedule of Significant Option Groups Outstanding (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares | shares	506
Options Exercisable, Shares | shares	256
Options Outstanding, Weighted-Average Exercise Price	$ 19.06
Options Exercisable, Weighted-Average Exercise Price	$ 8.31
$1.48 - $2.58
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	1 year 2 months 23 days
Options Outstanding, Shares | shares	67
Options Exercisable, Shares | shares	67
Range Of Exercise Prices, Lower Limit	$ 1.48
Range Of Exercise Prices, Upper Limit	2.58
Options Outstanding, Weighted-Average Exercise Price	1.83
Options Exercisable, Weighted-Average Exercise Price	$ 1.83
$2.67 - $3.28
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	2 years 2 months 12 days
Options Outstanding, Shares | shares	103
Options Exercisable, Shares | shares	103
Range Of Exercise Prices, Lower Limit	$ 2.67
Range Of Exercise Prices, Upper Limit	3.28
Options Outstanding, Weighted-Average Exercise Price	2.69
Options Exercisable, Weighted-Average Exercise Price	$ 2.69
$7.71 - $19.43
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 years 4 months 28 days
Options Outstanding, Shares | shares	166
Options Exercisable, Shares | shares	68
Range Of Exercise Prices, Lower Limit	$ 7.71
Range Of Exercise Prices, Upper Limit	19.43
Options Outstanding, Weighted-Average Exercise Price	18.59
Options Exercisable, Weighted-Average Exercise Price	$ 18.02
$28.56 - $47.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 7 months 13 days
Options Outstanding, Shares | shares	170
Options Exercisable, Shares | shares	18
Range Of Exercise Prices, Lower Limit	$ 28.56
Range Of Exercise Prices, Upper Limit	47.70
Options Outstanding, Weighted-Average Exercise Price	36.30
Options Exercisable, Weighted-Average Exercise Price	$ 28.56

Stock Based Compensation (Detai

Stock Based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 33,577	$ 34,097	$ 30,750
Income tax benefit	(12,036)	(10,462)	(8,752)
Total stock-based compensation expense after income taxes	21,541	23,635	21,998
Cost Of Revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	3,129	3,212	3,153
Engineering And Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	9,181	9,370	9,458
Selling and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 21,267	$ 21,515	$ 18,139

Savings Plan - Additional Infor

Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Savings Plan [Line Items]
Savings plan maximum percentage of employees contribution allowable	20.00%
Percentage of employer contributions vested per year	25.00%
Maximum employment period considered for vesting of employers' contribution, in years	4 years
Liability, Retirement and Postemployment Benefits	$ 24.4	$ 23.4
U.S. Qualified Pension Plan
Savings Plan [Line Items]
Maximum percentage of matching contributions made by the employer	100.00%	100.00%	100.00%
Percentage of employer match on employee contribution	4.00%	4.00%	4.00%
Savings Plan
Savings Plan [Line Items]
Amounts charged to statements of operations	$ 17.2	$ 15.3	$ 14.5

Schedule of Income (Loss) Befor

Schedule of Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

[1],[2]

Sep. 30, 2018

[2],[3]

Jul. 01, 2018

[2],[4]

Apr. 01, 2018

[5]

Dec. 31, 2017

[6],[7]

Oct. 01, 2017

[7],[8]

Jul. 02, 2017

[7],[9]

Apr. 02, 2017

[10]

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Income Tax Disclosure [Line Items]

U.S.

$ 189,691

$ 76,699

$ (341,018)

Non-U.S.

278,110

447,713

285,958

Income (loss) before income taxes

$ 111,128

$ 140,841

$ 120,012

$ 95,820

$ 98,084

$ 127,437

$ 206,877

$ 92,016

$ 467,801

$ 524,412

$ (55,060)

[1]

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.

[2]

Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[3]

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.

[4]

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.

[5]

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.

[6]

Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.

[7]

Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.

[8]

Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.

[9]

Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.

[10]

Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Schedule of Provision (Benefit)

Schedule of Provision (Benefit) for Income Taxes from Operations (Detail) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2018	[1],[2]	Sep. 30, 2018	[2],[3]	Jul. 01, 2018	[2],[4]	Apr. 01, 2018	[5]	Dec. 31, 2017	[6],[7]	Oct. 01, 2017	[7],[8]	Jul. 02, 2017	[7],[9]	Apr. 02, 2017	[10]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Current, U.S. Federal																	$ (59,122)	$ 162,679	$ 7,750
Current, Non-U.S.																	45,083	64,313	41,579
Current, State																	1,721	2,623	1,968
Current, Total																	(12,318)	229,615	51,297
Deferred, U.S. Federal																	29,252	43,687	(51,482)
Deferred, Non-U.S.																	(1,243)	(6,476)	(9,240)
Deferred, State																	331	(106)	(2,214)
Deferred, Total																	28,340	37,105	(62,936)
Total provision (benefit) for income taxes	$ (32,662)		$ 20,863		$ 18,975		$ 8,846		$ 204,007		$ 24,017		$ 31,901		$ 6,795		$ 16,022	$ 266,720	$ (11,639)
[1]	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.
[2]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[3]	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.
[4]	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.
[5]	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.
[6]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[7]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[8]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[9]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[10]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018		Sep. 30, 2018	[2],[3]	Jul. 01, 2018	[2],[4]	Apr. 01, 2018	[5]	Dec. 31, 2017		Oct. 01, 2017	[7],[8]	Jul. 02, 2017	[7],[9]	Apr. 02, 2017	[10]	Dec. 31, 2018	Dec. 31, 2017	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Total (benefit) provision for income taxes		$ (32,662)	[1],[2]	$ 20,863		$ 18,975		$ 8,846		$ 204,007	[6],[7]	$ 24,017		$ 31,901		$ 6,795		$ 16,022	$ 266,720		$ (11,639)
Effective tax rate																		3.40%	50.90%		21.10%
Provisional amount of additional income tax expense		(49,500)								186,000
Transition tax on mandatory deemed repatriation of foreign earnings																		$ (51,700)	$ 161,000
Expense related to remeasurement of deferred tax assets and liabilities																			33,600
Expense (benefit) associated with impact of correlative adjustments on tax positions																		2,200	(10,300)
Tax savings due to the tax holiday																		$ 11,900	$ 24,800		$ 17,000
Tax savings due to the tax holiday, per share																		$ 0.06	$ 0.12		$ 0.08
Tax holiday expiration date																		December 31, 2020
Valuation allowance includes net deferred tax assets		69,852								63,919								$ 69,852	$ 63,919
Tax credit carryforwards, approximately										98,400									98,400
Tax credits carryforwards		69,091								76,083								69,091	76,083
Reduction in un recognized tax benefits		43,395								36,263								43,395	36,263		$ 38,958	$ 36,792
Unrecognized tax benefits, if recognized would impact effective tax rate		30,700																30,700
Unrecognized tax benefits, if recognized would impact deferred taxes		12,600																12,600
Accrued interest and penalties		300								300								300	300
Interest and penalties related to income tax, expense (benefit)																		100	(100)		$ (100)
Deferred tax		5,900																5,900
Reduction of federal of state benefit reserves																		2,000
Unrecognized Tax Benefits, Period Increase (Decrease)																		200
Subsequent Event [Member]
Income Taxes [Line Items]
Total (benefit) provision for income taxes	$ 27,900
Reduction in un recognized tax benefits	$ 33,800
United States
Income Taxes [Line Items]
Tax credits carryforwards, business										900									$ 900
Tax credit carryforward, expiration date																			2,028
State and Local Jurisdiction
Income Taxes [Line Items]
Provisional amount of additional income tax expense		49,500								186,000
Transition tax on mandatory deemed repatriation of foreign earnings																		51,700
Expense (benefit) associated with impact of correlative adjustments on tax positions																				$ 10,300
Tax credits carryforwards										97,500									$ 97,500
Reduction in un recognized tax benefits		$ 43,400																$ 43,400
State and Local Jurisdiction | Earliest Tax Year
Income Taxes [Line Items]
Tax credit carryforward, expiration date																			2,019
State and Local Jurisdiction | Latest Tax Year
Income Taxes [Line Items]
Tax credit carryforward, expiration date																			2,038
State and Local Jurisdiction | Do Not Expire
Income Taxes [Line Items]
Tax credits carryforwards										$ 55,600									$ 55,600
[1]	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.
[2]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[3]	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.
[4]	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.
[5]	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.
[6]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[7]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[8]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[9]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[10]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Schedule of Reconciliation of E

Schedule of Reconciliation of Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
U.S. statutory federal tax rate	21.00%	35.00%	35.00%
U.S. transition tax	(10.50%)	28.70%
U.S, foreign derived intangible income	(1.80%)
Impact of rate change on deferred tax	0.30%	6.90%
Uncertain tax positions	1.00%	1.70%	(2.60%)
Foreign taxes	(2.00%)	(16.30%)	78.00%
Foreign tax credits	(2.20%)	(2.20%)	49.10%
U.S. research and development credit	(2.20%)	(1.60%)	15.80%
Equity compensation	(1.20%)	(0.80%)	(2.70%)
State income taxes, net of federal tax benefit	0.10%	(0.40%)	2.30%
Domestic production activities deduction		(0.30%)	2.30%
Goodwill impairment			(162.10%)
U.S. alternative minimum tax credit			3.70%
Inventory cost capitalization			1.80%
Other, net	0.90%	0.20%	0.50%
Effective tax rate, Total	3.40%	50.90%	21.10%

Schedule of Components of Defer

Schedule of Components of Deferred Tax Assets Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Tax credits	$ 69,091	$ 76,083
Accruals	20,826	22,602
Pension liabilities	23,449	27,508
Inventory valuations	18,514	17,793
Deferred revenue	9,130	9,016
Equity compensation	7,190	6,861
Vacation accrual	4,772	4,747
Net operating loss carryforwards	3,658	5,440
Marketable securities	962
Other	685	713
Gross deferred tax assets	158,277	170,763
Less: valuation allowance	(69,852)	(63,919)
Total deferred tax assets	88,425	106,844
Intangible assets	(24,211)	(16,120)
Depreciation	(14,028)	(12,293)
Marketable securities		(1,125)
Total deferred tax liabilities	(38,239)	(29,538)
Net deferred assets	$ 50,186	$ 77,306

Summary of Operating Loss Carry

Summary of Operating Loss Carryforwards (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	$ 48,195
Foreign Operating Loss Carryforwards	4,505
2,019
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	258
Foreign Operating Loss Carryforwards
2,020
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	269
Foreign Operating Loss Carryforwards
2,021
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	2,977
Foreign Operating Loss Carryforwards
2,022
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	5,749
Foreign Operating Loss Carryforwards
2,023
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	6,241
Foreign Operating Loss Carryforwards
2024-2028
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	4,672
Foreign Operating Loss Carryforwards
2029-2033
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	22,724
Foreign Operating Loss Carryforwards	44
Beyond 2,033
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards	5,305
Foreign Operating Loss Carryforwards	72
Non-Expiring
Operating Loss Carryforwards [Line Items]
State Operating Loss Carryforwards
Foreign Operating Loss Carryforwards	$ 4,389

Schedule of Unrecognized Tax Be

Schedule of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Beginning balance, as of January 1	$ 36,263	$ 38,958	$ 36,792
Tax positions for current year, Additions	4,716	8,208	9,766
Tax positions for prior years, Additions	2,626	199	187
Tax positions for prior years, Reductions	(153)	(10,573)	(1,960)
Expiration of statutes, Reductions	(57)	(325)	(3,532)
Settlements with tax authorities, Reductions		(204)	(2,295)
Ending balance as of December 31	$ 43,395	$ 36,263	$ 38,958

Operating Segment, Geographic_3

Operating Segment, Geographic and Significant Customer Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018SegmentCustomer	Dec. 31, 2017Customer	Dec. 31, 2016Customer
Segment Reporting Information [Line Items]
Operating segments | Segment	4
Number of customer accounted for more than ten percent of consolidated revenue | Customer	0	1	1
Consolidated Revenue
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%
Semiconductor Test | Consolidated Revenue | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	13.00%	22.00%	26.00%
Semiconductor Test | Customer 1 | Consolidated Revenue | Revenue from Rights Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage		13.00%	12.00%
Semiconductor Test | Customer 2 | Consolidated Revenue | Revenue from Rights Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage			12.00%

Schedule of Segment Information

Schedule of Segment Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	[1]	$ 2,100,802	$ 2,136,606	$ 1,753,250
Income (loss) before taxes	[2],[3]	467,801	524,411	(55,060)
Total assets	[4]	2,706,606	3,109,545	2,762,493
Property additions		114,379	105,375	85,272
Depreciation and amortization expense		113,224	108,075	120,009
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		1,492,417	1,662,549	1,368,169
Income (loss) before taxes	[2],[3]	397,645	491,361	311,939
Total assets	[4]	669,452	597,480	557,546
Property additions		94,496	87,920	70,543
Depreciation and amortization expense		58,095	58,901	58,087
System Test
Segment Reporting Information [Line Items]
Revenues		216,132	192,135	189,846
Income (loss) before taxes	[2],[3]	48,857	10,305	28,916
Total assets	[4]	88,098	97,018	110,361
Property additions		3,469	5,976	3,788
Depreciation and amortization expense		6,430	6,646	6,551
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		261,452	170,056	99,031
Income (loss) before taxes	[2],[3]	7,670	8,763	(16,783)
Total assets	[4]	607,502	368,037	317,635
Property additions		11,188	7,044	6,755
Depreciation and amortization expense		36,755	25,711	26,869
Wireless Test
Segment Reporting Information [Line Items]
Revenues		132,006	111,866	96,204
Income (loss) before taxes	[2],[3]	29,052	17,350	(371,409)
Total assets	[4]	77,570	59,912	62,366
Property additions		5,226	4,435	4,186
Depreciation and amortization expense		5,328	5,392	25,921
Corporate And Eliminations
Segment Reporting Information [Line Items]
Revenues		(1,205)
Income (loss) before taxes	[2],[3]	(15,423)	(3,368)	(7,723)
Total assets	[4]	1,263,984	1,987,098	1,714,585
Depreciation and amortization expense		$ 6,616	$ 11,425	$ 2,581
[1]	Revenues attributable to a country are based on location of customer site.
[2]	Included in Corporate and Other are: contingent consideration adjustments, pension and postretirement plans actuarial gains (losses), severance charges, impairment of fixed assets and expenses related to the Japan earthquake, property insurance recovery, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations and acquisition related charges.
[3]	Included in income (loss) before taxes are charges and credits related to restructuring and other, and inventory charges. In 2016, loss before income taxes in Wireless Test also included charges related to goodwill and acquired intangible assets impairment.
[4]	Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.

Schedule of Segment Reporting I

Schedule of Segment Reporting Information by Segment Charges (Detail) - USD ($) $ in Thousands	3 Months Ended																	12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jul. 01, 2018		Apr. 01, 2018		Dec. 31, 2017		Oct. 01, 2017		Jul. 02, 2017		Apr. 02, 2017		Jul. 03, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Acquisition related costs	$ 500		$ 800		$ 2,500		$ 800											$ 4,500
Restructuring and other-employee severance	11,446	[1],[2]	1,710	[2],[3]	2,389	[2],[4]	(313)	[5]	$ 8,970	[6],[7]	$ (4,407)	[7],[8]	$ 2,288	[7],[9]	$ 2,511	[10]		15,232	$ 9,362	$ 21,942
Goodwill impairment charge																				254,946
Intangible assets impairment charge																		8,800		83,339
Contingent consideration adjustment																		987	7,820	15,896
Universal Robots (UR)
Segment Reporting Information [Line Items]
Contingent consideration adjustment	7,400		$ 800		$ 3,500		$ 5,000		$ 6,000		$ (300)		$ 1,500		$ 600			(16,700)	7,800	15,300
Mobile Industrial Robots (MiR)
Segment Reporting Information [Line Items]
Contingent consideration adjustment	$ 17,700																	17,700
Semiconductor Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge																		6,822	4,606	9,656
Semiconductor Test | Fixed Assets [Member]
Segment Reporting Information [Line Items]
Restructuring and other-employee severance																			1,124
Semiconductor Test | Severance And Benefits
Segment Reporting Information [Line Items]
Restructuring and other-employee severance																		8,429	1,779	2,860
System Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge																		1,175	1,918	630
Industrial Automation
Segment Reporting Information [Line Items]
Acquisition related costs																		1,163
Cost of revenues-inventory charge																		680
Restructuring and other-employee severance																			1,414	585
Wireless Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge																		2,565	2,190	7,207
Restructuring and other-lease impairment																			972
Restructuring and other-employee severance																				2,650
Goodwill impairment charge																	$ 254,900			254,946
Intangible assets impairment charge																	$ 83,300			83,339
Corporate And Eliminations | Restructuring and other
Segment Reporting Information [Line Items]
Acquisition related costs																		3,422
Restructuring and other																		872
Property insurance recovery																			(5,064)	(5,051)
Corporate And Eliminations | Universal Robots (UR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment																		(16,679)	7,820	15,346
Corporate And Eliminations | Impairment of Fixed Assets and Expenses Related to the Japan Earthquake | Restructuring and other
Segment Reporting Information [Line Items]
Building impairment and other expenses																			$ 755	$ 5,051
Corporate And Eliminations | Mobile Industrial Robots (MiR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment																		$ 17,666
[1]	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.
[2]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[3]	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.
[4]	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.
[5]	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.
[6]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[7]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[8]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[9]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[10]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Schedule of Revenues by Country

Schedule of Revenues by Country (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	$ 2,100,802	$ 2,136,606	$ 1,753,250
TAIWAN
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	516,322	687,031	653,076
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	348,942	260,451	174,876
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	282,869	252,516	221,948
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	223,207	163,715	117,671
KOREA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	163,224	206,819	147,882
JAPAN
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	158,281	169,093	135,978
MALAYSIA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	122,797	124,048	103,472
SINGAPORE
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	108,618	101,085	73,172
PHILIPPINES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	77,996	105,850	54,705
THAILAND
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	59,184	29,566	43,097
Rest Of The World
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from unaffiliated customers	[1]	$ 39,362	$ 36,432	$ 27,373
[1]	Revenues attributable to a country are based on location of customer site.

Schedule of Long-Lived Assets b

Schedule of Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets		$ 279,821	$ 268,447
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets		209,368	198,855
Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	[1]	$ 70,453	$ 69,592
[1]	As of December 31, 2018 and 2017, long-lived assets attributable to Singapore were $19.4 million and $23.6 million, respectively.

Schedule of Long-Lived Assets_2

Schedule of Long-Lived Assets by Geographic Area (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 279,821	$ 268,447
SINGAPORE
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 19,400	$ 23,600

Stock Repurchase Program - Addi

Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 31, 2018	Jan. 31, 2015
Stock Repurchase Programs [Line Items]
Stock repurchase program, authorized amount				$ 500,000,000
Stock Repurchased During Period, Shares				6.8
Cumulative repurchases, value		$ 832,356,000	$ 200,304,000	$ 146,331,000
Treasury stock average price per share				$ 21.39
Cumulative repurchases, shares		21.6	5.8	22.5
Cumulative repurchases, value		$ 823,500,000	$ 200,000,000	$ 446,000,000
Common stock average price		$ 38.06	$ 34.30	$ 19.87
Scenario, Forecast
Stock Repurchase Programs [Line Items]
Cumulative repurchases, value	$ 500,000,000
Maximum
Stock Repurchase Programs [Line Items]
Stock repurchase program, authorized amount					$ 1,500,000,000	$ 500,000,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event	1 Months Ended
	Jan. 31, 2019$ / shares
Subsequent Event [Line Items]
Cash Dividends payable, amount per share	$ 0.09
Cash Dividends payable, date to be paid	Mar. 22, 2019
Cash Dividends payable, record date	Feb. 22, 2019

Consolidated Quarterly Statemen

Consolidated Quarterly Statements of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2018	[1],[2]	Sep. 30, 2018	[2],[3]	Jul. 01, 2018	[2],[4]	Apr. 01, 2018	[5]	Dec. 31, 2017	[6],[7]	Oct. 01, 2017	[7],[8]	Jul. 02, 2017	[7],[9]	Apr. 02, 2017	[10]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information [Line Items]
Total revenues	$ 519,558		$ 566,848		$ 526,929		$ 487,467		$ 479,415		$ 503,378		$ 696,901		$ 456,913		$ 2,100,802	$ 2,136,606	$ 1,753,250
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	210,023		233,155		219,595		217,635		208,485		208,509		306,263		191,897		880,408	915,153	794,642
Gross profit	309,535		333,693		307,334		269,832		270,930		294,869		390,638		265,016		1,220,394	1,221,453	958,608
Selling and administrative	100,552		100,202		99,410		90,505		87,880		86,130		90,111		84,792		390,669	348,913	316,544
Engineering and development	74,706		77,049		75,342		74,408		72,070		76,986		82,270		75,978		301,505	307,305	292,159
Acquired intangible assets amortization	10,558		11,142		9,793		7,698		7,384		7,028		8,166		7,952		39,191	30,530	52,648
Restructuring and other	11,446		1,710		2,389		(313)		8,970		(4,407)		2,288		2,511		15,232	9,362	21,942
Total operating expenses	197,262		190,103		186,934		172,298		176,304		165,737		182,835		171,233		746,597	696,110	1,021,578
Income (loss) from operations	112,273		143,590		120,400		97,534		94,626		129,132		207,803		93,783		473,797	525,343	(62,970)
Interest income	(9,083)		(6,213)		(5,427)		(5,981)		(6,476)		(4,517)		(3,292)		(3,520)		(26,704)	(17,805)	(9,296)
Interest expense	13,182		5,557		5,639		6,890		5,380		5,372		5,509		5,402		31,269	21,663	3,637
Other (income) expense, net	(2,954)		3,405		176		805		(2,362)		840		(1,291)		(115)		1,431	(2,927)	(2,251)
Income (loss) before income taxes	111,128		140,841		120,012		95,820		98,084		127,437		206,877		92,016		467,801	524,412	(55,060)
Income tax provision (benefit)	(32,662)		20,863		18,975		8,846		204,007		24,017		31,901		6,795		16,022	266,720	(11,639)
Net income (loss)	$ 143,790		$ 119,978		$ 101,037		$ 86,974		$ (105,923)		$ 103,420		$ 174,976		$ 85,221		$ 451,779	$ 257,692	$ (43,421)
Net income (loss) per common share-basic	$ 0.80		$ 0.65		$ 0.53		$ 0.45		$ (0.54)		$ 0.52		$ 0.88		$ 0.43		$ 2.41	$ 1.30	$ (0.21)
Net income (loss) per common share-diluted	0.79		0.63		0.52		0.43		(0.54)		0.52		0.87		0.42		2.35	1.28	(0.21)
Cash dividend declared per common share	$ 0.09		$ 0.09		$ 0.09		$ 0.09		$ 0.07		$ 0.07		$ 0.07		$ 0.07		$ 0.36	$ 0.28	$ 0.24
Product [Member]
Quarterly Financial Information [Line Items]
Total revenues	$ 420,652		$ 470,994		$ 434,051		$ 403,925		$ 388,282		$ 412,854		$ 610,356		$ 373,204		$ 1,729,621	$ 1,784,695	$ 1,453,248
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	170,064		195,339		180,777		180,958		168,672		169,661		267,752		154,883		727,138	760,967	660,056
Service [Member]
Quarterly Financial Information [Line Items]
Total revenues	98,906		95,854		92,878		83,542		91,133		90,524		86,545		83,709		371,181	351,911	300,002
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 39,959		$ 37,816		$ 38,818		$ 36,677		$ 39,813		$ 38,848		$ 38,511		$ 37,014		$ 153,270	$ 154,186	$ 134,586
[1]	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.
[2]	Teradyne recorded pension and post retirement net actuarial (gains) losses of $(0.1) million, $0.3 million and $(3.5) million for the second, third and fourth quarter in 2018, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[3]	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.
[4]	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.
[5]	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.
[6]	Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[7]	Teradyne recorded pension and post retirement net actuarial gains of $2.8 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: “Accounting Policies” for a discussion of Teradyne’s accounting policy.
[8]	Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[9]	Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[10]	Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.

Consolidated Quarterly Statem_2

Consolidated Quarterly Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information [Line Items]
Contingent consideration fair value adjustment									$ 987	$ 7,820	$ 15,896
Severance benefit and charges	$ 800	$ 1,700	$ 2,400	$ 3,900	$ 1,800	$ 600	$ 800	$ 600
Acquisition related expense and compensation	500	800	2,500	800					4,500
Impairment of fixed assets					1,100
Pension and post retirement net actuarial (gains) losses	(3,500)	300	(100)		(3,800)		(2,800)
Impairment of Fixed Assets and Expenses Related to the Japan Earthquake
Quarterly Financial Information [Line Items]
Property insurance recovery						5,100				5,100	5,100
Impairment of Fixed Assets and Expenses Related to the Japan Earthquake | Earthquake Related Expenses
Quarterly Financial Information [Line Items]
Impairment of fixed assets and other expenses						800				800	900
Universal Robots (UR)
Quarterly Financial Information [Line Items]
Contingent consideration fair value adjustment	7,400	$ 800	$ 3,500	$ 5,000	$ 6,000	(300)	$ 1,500	600	(16,700)	$ 7,800	$ 15,300
Mobile Industrial Robots (MiR)
Quarterly Financial Information [Line Items]
Contingent consideration fair value adjustment	$ 17,700								$ 17,700
Wireless Test
Quarterly Financial Information [Line Items]
Lease impairment								$ 1,300
Previously impaired lease termination						$ 400

Valuation and Qualifying Acco_2

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 2,219	$ 2,356	$ 2,407
Additions Charged to Cost and Expenses		4
Other	20
Deductions	566	141	51
Balance at End of Period	1,673	2,219	2,356
Inventory Reserve
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	102,896	116,016	119,376
Additions Charged to Cost and Expenses	11,242	8,844	17,493
Other	368	(126)	4,417
Deductions	13,727	21,838	25,270
Balance at End of Period	100,779	102,896	116,016
Valuation Allowance of Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	63,919	48,369	43,039
Additions Charged to Cost and Expenses	6,333	15,571	5,413
Other
Deductions	400	21	83
Balance at End of Period	$ 69,852	$ 63,919	$ 48,369