XML 96 R77.htm IDEA: XBRL DOCUMENT
v3.20.4

Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | $ 601,976 | $ 211,596
Available-for-sale marketable securities, Unrealized Gain | 9,077 | 4,687
Available-for-sale marketable securities, Unrealized (Loss) | (213) | (262)
Available-for-sale marketable securities, Fair Market Value | 610,840 | 216,021
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 70,418 | 23,999
Marketable securities |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 522,228 | 137,144
Available-for-sale marketable securities, Unrealized Gain | 92 | 160
Available-for-sale marketable securities, Unrealized (Loss) | (40) | (1)
Available-for-sale marketable securities, Fair Market Value | 522,280 | 137,303
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 61,806 | 2,922
Long-term marketable securities |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 79,748 | 74,452
Available-for-sale marketable securities, Unrealized Gain | 8,985 | 4,527
Available-for-sale marketable securities, Unrealized (Loss) | (173) | (261)
Available-for-sale marketable securities, Fair Market Value | 88,560 | 78,718
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | $ 8,612 | $ 21,077

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ter_MarketableSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ter_LongTermMarketableSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |