XML 18 R55.htm IDEA: XBRL DOCUMENT
v2.4.0.8

SHAREHOLDERS' EQUITY (Details) (USD $) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Nov. 30, 2013 | Apr. 30, 2013 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2007
Authorized Shares [Roll forward] |  |  |  |  |  |
Balance at beginning of period (in shares) |  |  | 90,000,000 | 90,000,000 | 51,200,000 |
Increased authorized share capital (in shares) |  |  |  |  | 38,800,000 |
Balance at end of period (in shares) |  |  | 90,000,000 | 90,000,000 | 90,000,000 |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |
Balance at beginning of period, issued (in shares) |  |  | 52,915,639 | 47,303,394 | 46,898,782 |
Balance at beginning of period, outstanding (in shares) |  |  | 52,915,639 | 47,303,394 | 46,898,782 |
Balance at end of period, issued (in shares) |  |  | 75,382,001 | 52,915,639 | 47,303,394 |
Balance at end of period, outstanding (in shares) |  |  | 75,382,001 | 52,915,639 | 47,303,394 |
Common Stock [Roll forward] |  |  |  |  |  |
Balance at beginning of period |  |  | $ 529,000 | $ 473,000 | $ 469,000 |
Common Shares Issued in Follow-on Offering |  |  | 206,000 | 55,000 |  |
Compensation |  |  | 2,093,000 | 1,258,000 | 1,320,000 |
Common Shares Issued, 2011 Equity Incentive Plan |  |  |  |  | 4,000 |
Balance at end of period |  |  | 754,000 | 529,000 | 473,000 |
Common Stock [Abstract] |  |  |  |  |  |
Common shares issued in public offering (in shares) | 9,343,750 | 11,212,500 | 20,556,250 | 5,500,000 |  |
Net proceeds from underwritten public offering of common shares | 70,900,000 | 102,200,000 | 172,611,000 | 75,582,000 | 4,000 |
Common Stock, par value (in dollars per share) |  |  | $ 0.01 | $ 0.01 | $ 0.01 |
Additional Paid in Capital [Abstract] |  |  |  |  |  |
Share Premium Fund |  |  | 172,400,000 | 0 |  |
Reduction of Share Premium |  |  |  | 75,600,000 |  |
Contributed Surplus Account [Abstract] |  |  |  |  |  |
Net Income (Loss) |  |  | 105,417,000 | 73,192,000 | 72,298,000 |
Shareholders' Rights Plan [Abstract] |  |  |  |  |  |
Preferred stock purchase right |  |  |  |  |  | one preferred stock purchase right to purchase one one-thousandth of a share of our Series A Participating Preferred Stock for each outstanding share of our common stock, par value $0.01 per share
Stockholders rights, exercise price (in dollars per share) |  |  |  |  |  | $ 115
Percentage of common stock ownership (in hundredths) |  |  |  |  |  | 15.00%
Employees and Non-Employees [Member] |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |
Shares held in treasury (in shares) |  |  | 23,000 |  |  |
Restricted Stock Awards [Member] | Scandic American Shipping Ltd. [Member] |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |
Common Stock, par value (in dollars per share) |  |  |  | $ 0.01 |  |
Restricted shares issued and outstanding (in shares) |  |  | 690,551 | 690,551 | 578,306 |
Restricted Stock Awards [Member] | Employees and Non-Employees [Member] | Stock Incentive Plan 2011 [Member] |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |
Shares held in treasury (in shares) |  |  | 14,500 | 8,500 |  |
Restricted shares issued and outstanding (in shares) |  |  | 40,000 | 217,500 | 226,000 |
Common Stock [Member] |  |  |  |  |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |
Compensation - Restricted Shares (in shares) |  |  | 1,910,112 | 112,245 | 4,612 |
Common Shares Issued, 2011 Equity Incentive Plan (in shares) |  |  |  |  | 400,000 |
Common Stock [Abstract] |  |  |  |  |  |
Common shares issued in public offering (in shares) |  |  | 20,556,250 | 5,500,000 |  |
Shares held in treasury (in shares) |  |  | 14,500 | 8,500 |  |
Contributed Surplus Account [Abstract] |  |  |  |  |  |
Net Income (Loss) |  |  | 0 | 0 | 0 |
Restricted Stock [Member] |  |  |  |  |  |
Common Stock [Roll forward] |  |  |  |  |  |
Compensation |  |  | $ 19,000 | $ 1,000 | $ 0 |

X
- Details
Name: | nat_AuthorizedSharesRollForward
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | nat_CommonStockAbstract
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Common shares issued under equity incentive plan 2011. + References No definition available. + Details
Name: | nat_CommonStockIssued
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Common shares issued under equity incentive plan 2011. + References No definition available. + Details
Name: | nat_CommonStockIssuedShares
Namespace Prefix: | nat_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | nat_CommonStockRollForward
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | nat_ContributedSurplusAccountAbstract
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The increase in maximum number of common shares permitted to be issued by an entity's charter and bylaws. + References No definition available. + Details
Name: | nat_IncreasedAuthorizedShareCapital
Namespace Prefix: | nat_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increase (decrease) of the balance of share premium fund during the period. + References No definition available. + Details
Name: | nat_IncreaseDecreaseOfSharePremiumFund
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | nat_IssuedAndOutstandingSharesRollForward
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Description of preferred stock purchase right to acquire shares of preferred stock. + References No definition available. + Details
Name: | nat_PreferredStockPurchaseRight
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | nat_ShareholdersRightsPlanAbstract
Namespace Prefix: | nat_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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
- Definition Gross number of restricted shares (or other type of equity) issued and outstanding as of balance sheet date. + References No definition available. + Details
Name: | nat_StockIssuedAndOutstandingRestrictedSharesShareBasedCompensationGross
Namespace Prefix: | nat_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Gross number of restricted shares issued and outstanding as of balance sheet date. + References No definition available. + Details
Name: | nat_StockIssuedAndOutstandingSharesRestrictedStockAwardGross
Namespace Prefix: | nat_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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 No definition available. + Details
Name: | nat_StockIssuedFollowOnOfferingValue
Namespace Prefix: | nat_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_AdditionalPaidInCapitalAbstract
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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
Name: | us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | num: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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + 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://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
Name: | us-gaap_CommonStockSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Value of all classes of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares exclude common shares repurchased by the entity and held as treasury shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
Name: | us-gaap_CommonStockValueOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 20 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Other Comprehensive Income -URI http://asc.fasb.org/extlink&oid=6519514 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Net Income -URI http://asc.fasb.org/extlink&oid=6518256 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.19) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.18) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.22) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e565-108580 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 19 -Article 5 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash inflow from the additional capital contribution to the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfCommonStock
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
Name: | us-gaap_ShareBasedCompensation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Price of a single share of a number of saleable stocks of a company. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
Name: | us-gaap_SharePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of new stock issued during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares that have been repurchased during the period and are being held in treasury. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 + Details
Name: | us-gaap_TreasuryStockSharesAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration