XML 54 R62.htm IDEA: XBRL DOCUMENT
v3.20.1

Investments - Contractual Maturities of Debt Securities and Other Investments (Detail) - USD ($) $ in Thousands | Mar. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities, Fair Value/Carrying Value | $ 37,860 | $ 37,700 | $ 37,660
Corporate Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Less than one year | 3,274 |  |
One to two years | 3,702 |  |
Two to three years | 1,947 |  |
Available-for-sale debt securities, Fair Value/Carrying Value | 8,923 |  | 9,384
Municipal Fixed-Rate Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
One to two years | 934 |  |
Available-for-sale debt securities, Fair Value/Carrying Value | 934 |  | 930
Asset-Backed Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Less than one year | 101 |  |
One to two years | 389 |  |
Two to three years | 1,559 |  |
Three to five years | 2,174 |  |
Five to ten years | 1,505 |  |
More than ten years | 265 |  |
Available-for-sale debt securities, Fair Value/Carrying Value | 5,993 |  | 6,890
Mortgage/Agency-Backed Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
One to two years | 584 |  |
Two to three years | 1,769 |  |
Three to five years | 107 |  |
Five to ten years | 1,655 |  |
More than ten years | 4,352 |  |
Available-for-sale debt securities, Fair Value/Carrying Value | 8,467 |  | 6,962
U.S. Government Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Less than one year | 61 |  |
One to two years | 5,376 |  |
Two to three years | 7,285 |  |
Three to five years | 379 |  |
Available-for-sale debt securities, Fair Value/Carrying Value | 13,101 |  | $ 12,323
Other [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Less than one year | 442 |  |
Available-for-sale debt securities, Fair Value/Carrying Value | $ 442 |  |

X
- Definition Amount of available-for-sale debt securities at fair value maturing after one year through two years. + References No definition available. + Details
Name: | adtn_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue
Namespace Prefix: | adtn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of available-for-sale debt securities at fair value maturing after three years through five years. + References No definition available. + Details
Name: | adtn_AvailableForSaleSecuritiesDebtMaturitiesAfterThreeThroughFiveYearsFairValue
Namespace Prefix: | adtn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of available-for-sale debt securities at fair value maturing after two year through three years. + References No definition available. + Details
Name: | adtn_AvailableForSaleSecuritiesDebtMaturitiesAfterTwoThroughThreeYearsFairValue
Namespace Prefix: | adtn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. + 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 (d) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27198-111563 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=75019621&loc=d3e62586-112803 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27198-111563 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 3 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=75019621&loc=d3e62586-112803 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in remainder of fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRemainderOfFiscalYearFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
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=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

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

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