XML 73 R54.htm IDEA: XBRL DOCUMENT
v3.25.1

SHAREHOLDERS' EQUITY (Details) |  | 1 Months Ended | 2 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Feb. 14, 2022 USD ($) | Jan. 31, 2025 USD ($) shares | Jan. 31, 2024 USD ($) shares | Feb. 14, 2022 USD ($) shares | Dec. 31, 2024 USD ($) $ / shares shares | Dec. 31, 2023 USD ($) $ / shares shares | Dec. 31, 2022 USD ($) shares | Sep. 29, 2021 USD ($) | Jun. 16, 2017 $ / shares
Authorized Shares [Roll forward] |  |  |  |  |  |  |  |  |
Balance at beginning of period (in shares) | shares |  | 360,000,000 | 360,000,000 |  | 360,000,000 |  |  |  |
Balance at end of period (in shares) | shares |  |  |  |  | 360,000,000 | 360,000,000 |  |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |  |  |  |
Balance at beginning of period, issued (in shares) | shares |  | 211,750,663 | 208,796,444 |  | 208,796,444 |  |  |  |
Balance at beginning of period, outstanding (in shares) | shares |  | 211,750,663 | 208,796,444 |  | 208,796,444 |  |  |  |
Balance at end of period, issued (in shares) | shares |  |  |  |  | 211,750,663 | 208,796,444 |  |  |
Balance at end of period, outstanding (in shares) | shares |  |  |  |  | 211,750,663 | 208,796,444 |  |  |
Common Stock [Roll forward] |  |  |  |  |  |  |  |  |
At-the-Market Offering, Value |  |  |  |  | $ 8,932,000 |  | $ 49,096,000 |  |
Additional Paid in Capital [Abstract] |  |  |  |  |  |  |  |  |
Share premium fund |  |  |  |  | 176,000,000 | $ 167,100,000 |  |  |
Stock option settlement payable |  |  |  |  | 4,400,000 |  |  |  |
Contributed Surplus Account [Abstract] |  |  |  |  |  |  |  |  |
Dividend charged to contribution surplus account |  |  |  |  | $ 83,600,000 | 102,300,000 |  |  |
Dividend declared (in dollars per share) | $ / shares |  |  |  |  | $ 0.4 |  |  |  |
Dividend paid |  |  | $ 12,500,000 |  | $ 75,100,000 | 89,800,000 | 22,700,000 |  |
Contribution to surplus account |  |  |  |  | $ 321,200,000 | $ 404,800,000 | 507,100,000 |  |
Shareholders' Rights Plan [Abstract] |  |  |  |  |  |  |  |  |
Preferred share purchase right |  |  |  |  |  |  |  |  | 0.001
Common share, par value (in dollars per share) | $ / shares |  |  |  |  | $ 0.01 | $ 0.01 |  |  |
Shareholders rights, exercise price (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  | $ 30
Percentage of common share ownership |  |  |  |  |  |  |  |  | 15.00%
Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Contributed Surplus Account [Abstract] |  |  |  |  |  |  |  |  |
Dividend paid |  | $ 8,500,000 |  |  |  |  |  |  |
60 Million 2021, ATM Program [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Gross amount of at-the-market offering of common stock |  |  |  | $ 16,900,000 |  |  |  |  |
At-the-market offering, gross amount utilized | $ 39,200,000 |  |  |  |  |  |  |  |
Net amount at-the-market offering of common stock |  |  |  | $ 16,500,000 |  |  |  |  |
Common shares issued (in shares) | shares |  |  |  | 10,764,990 |  |  |  |  |
60 Million 2021, ATM Program [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
At-the-market offering of common Stock |  |  |  |  |  |  |  | $ 60,000,000 |
60 Million 2022, ATM Program [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Gross amount of at-the-market offering of common stock |  |  |  |  | $ 9,200,000 |  | 33,600,000 |  |
Net amount at-the-market offering of common stock |  |  |  |  | $ 8,900,000 |  | $ 32,700,000 |  |
Common shares issued (in shares) | shares |  |  |  |  | 2,954,219 | 0 | 14,337,258 |  |
Remaining available proceeds from offering |  |  |  |  | $ 17,300,000 |  |  |  |
60 Million 2022, ATM Program [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |  |  |  |
At-the-Market Offering (in shares) | shares |  |  |  |  | 2,954,219 | 0 | 14,337,258 |  |
Common Stock [Roll forward] |  |  |  |  |  |  |  |  |
At-the-Market Offering, Value |  |  |  |  | $ 30,000 | $ 0 | $ 143,000 |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
At-the-market offering of common Stock | $ 60,000,000 |  |  | $ 60,000,000 |  |  |  |  |
Common Stock [Member] |  |  |  |  |  |  |  |  |
Authorized Shares [Roll forward] |  |  |  |  |  |  |  |  |
Balance at beginning of period (in shares) | shares |  | 360,000,000 | 360,000,000 | 360,000,000 | 360,000,000 | 360,000,000 | 360,000,000 |  |
Balance at end of period (in shares) | shares |  |  |  |  | 360,000,000 | 360,000,000 | 360,000,000 |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |  |  |  |
Balance at beginning of period, issued (in shares) | shares |  | 211,750,663 | 208,796,444 | 183,694,196 | 208,796,444 | 208,796,444 | 183,694,196 |  |
Balance at beginning of period, outstanding (in shares) | shares |  | 211,750,663 | 208,796,444 | 183,694,196 | 208,796,444 | 208,796,444 | 183,694,196 |  |
At-the-Market Offering (in shares) | shares |  |  |  |  | 2,954,219 |  | 25,102,248 |  |
Balance at end of period, issued (in shares) | shares |  |  |  |  | 211,750,663 | 208,796,444 | 208,796,444 |  |
Balance at end of period, outstanding (in shares) | shares |  |  |  |  | 211,750,663 | 208,796,444 | 208,796,444 |  |
Common Stock [Roll forward] |  |  |  |  |  |  |  |  |
Balance at beginning of period |  | $ 2,117,000 | $ 2,087,000 | $ 1,836,000 | $ 2,087,000 | $ 2,087,000 | $ 1,836,000 |  |
At-the-Market Offering, Value |  |  |  |  | 30,000 |  | 251,000 |  |
Balance at end of period |  |  |  |  | 2,117,000 | 2,087,000 | $ 2,087,000 |  |
Common Stock [Member] | 60 Million 2021, ATM Program [Member] |  |  |  |  |  |  |  |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |  |  |  |
At-the-Market Offering (in shares) | shares |  |  |  |  |  |  | 10,764,990 |  |
Common Stock [Roll forward] |  |  |  |  |  |  |  |  |
At-the-Market Offering, Value |  |  |  |  |  |  | $ 108,000 |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
At-the-market offering of common Stock |  |  |  |  |  |  | 60,000,000 |  |
Common Stock [Member] | 60 Million 2022, ATM Program [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
At-the-market offering of common Stock |  |  |  |  | $ 60,000,000 | $ 60,000,000 | $ 60,000,000 |  |

X
- Definition The Company has launched an At-the-Market Offering program refers to gross amount. + References No definition available. + Details
Name: | nat_AtTheMarketOfferingGrossAmount
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The Company has launched an At-the-Market Offering program, refers to gross amount utilized. + References No definition available. + Details
Name: | nat_AtTheMarketOfferingGrossAmountUtilized
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The Company has launched an At-the-Market Offering program refers to net amount. + References No definition available. + Details
Name: | nat_AtTheMarketOfferingNetAmount
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The Company has launched an At-the-Market Offering of our common stock and believes that the current cash and cash equivalents and cash expected to be generated from operations are sufficient to meet the working capital needs and other liquidity requirements for the next 12 months. + References No definition available. + Details
Name: | nat_AtTheMarketOfferingOfCommonStock
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of At-the-Market Offering of remaining available proceeds from offering. + References No definition available. + Details
Name: | nat_AtTheMarketOfferingRemainingAvailableProceedsFromOffering
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The Company has launched an At-the-Market Offering of our common stock and number of new stock issued. + References No definition available. + Details
Name: | nat_AtTheMarketOfferingStockIssuedDuringPeriodNewSharesIssued
Namespace Prefix: | nat_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | nat_AuthorizedSharesRollForward
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | nat_CommonStockRollForward
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The amount of dividend was charged to the portion of contributed surplus account. + References No definition available. + Details
Name: | nat_DividendChargedToContributionSurplusAccount
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | nat_IssuedAndOutstandingSharesRollForward
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage of common share ownership by any person that are subject to the entity's redemption of preferred share purchase rights. + References No definition available. + Details
Name: | nat_PercentageOfCommonShareOwnership
Namespace Prefix: | nat_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Refers to a dividend of one preferred share purchase right to acquire shares of preferred stock. + References No definition available. + Details
Name: | nat_PreferredSharePurchaseRight
Namespace Prefix: | nat_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount included in additional paid in capital, which cannot be distributed without certain legal procedures designed to protect the creditors of the Company. + References No definition available. + Details
Name: | nat_SharePremiumFund
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition The amount of liability account representing the obligation to settle stock options with a cash payment. + References No definition available. + Details
Name: | nat_StockOptionSettlementPayable
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Exercise price per share or per unit of warrants or rights outstanding. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481112/505-10-50-3 + Details
Name: | us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1 + Details
Name: | us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Face amount or stated value per share of common stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(16)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 + Details
Name: | us-gaap_CommonStockSharesAuthorized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_CommonStockSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481112/505-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.6-05(4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-2 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(4)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(16)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 + Details
Name: | us-gaap_CommonStockSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Value of common shares held by shareholders. Excludes common shares repurchased and held as treasury shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(16)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 + Details
Name: | us-gaap_CommonStockValueOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 15 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-15 + Details
Name: | us-gaap_PaymentsOfDividends
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number of new stock issued during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481112/505-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478448/946-505-50-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(4)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(i)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481112/505-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-11 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 205 -Name Accounting Standards Codification -Section 45 -Paragraph 4 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478009/946-205-45-4 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478448/946-505-50-2 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(4)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1 + Details
Name: | us-gaap_StockIssuedDuringPeriodValueNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The increase (decrease) in stockholders' equity during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481112/505-10-50-2 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-11 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 205 -Name Accounting Standards Codification -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478009/946-205-45-3 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478448/946-505-50-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1 + Details
Name: | us-gaap_StockholdersEquityPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsidiarySaleOfStockAxis=nat_AtTheMarketATM2021ProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsidiarySaleOfStockAxis=nat_AtTheMarketATM2022ProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |