XML 69 R52.htm IDEA: XBRL DOCUMENT
v3.21.1

FINANCIAL INSTRUMENTS AND OTHER FAIR VALUE DISCLOSURES (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Investment Securities | $ 0 | $ 825
Accordion loan amount | 30,000 |
Fair Value [Member] | Level 1 [Member] | Recurring [Member] |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Cash and Cash Equivalents | 57,847 | 48,847
Restricted Cash | 4,223 | 12,791
Investment Securities | 0 | 825
Fair Value [Member] | Level 2 [Member] | Recurring [Member] |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
2019 Senior Secured Credit Facility including $30 million Accordion Loan | (253,902) | (291,798)
Financing of 2018-built Vessels | (112,238) | (119,867)
Carrying Value [Member] | Level 1 [Member] | Recurring [Member] |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Cash and Cash Equivalents | 57,847 | 48,847
Restricted Cash | 4,223 | 12,791
Investment Securities | 0 | 825
Carrying Value [Member] | Level 2 [Member] | Recurring [Member] |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
2019 Senior Secured Credit Facility including $30 million Accordion Loan | (253,902) | (291,798)
Financing of 2018-built Vessels | $ (112,238) | $ (119,867)

X
- Definition Fair value portion of restricted cash. + References No definition available. + Details
Name: | nat_RestrictedCashFairValueDisclosure
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of contractual arrangement with a lender under which borrowings can be made up to a specific amount at any point in time. + References No definition available. + Details
Name: | nat_SeniorSecuredCreditFacilityIncludingAccordionLoanFairValueDisclosure
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
Name: | us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits. + References No definition available. + Details
Name: | us-gaap_DepositsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
Name: | us-gaap_EquitySecuritiesFvNi
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of contractual arrangement with a lender under which borrowings can be made up to a specific amount at any point in time. + References No definition available. + Details
Name: | us-gaap_LinesOfCreditFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |