XML 24 R50.htm IDEA: XBRL DOCUMENT
v2.4.0.6

DEFERRED COMPENSATION LIABILITY (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Post Retirement Benefits With Individual Employees [Line Items] |  |  |
Total expense recognized | $ 1,391 | $ 1,741 | $ 2,450
Executive Vice President and Chief Financial Officer [Member] |  |  |
Post Retirement Benefits With Individual Employees [Line Items] |  |  |
Required service period (in years) | 20.5Y |  |
Maximum benefit as a percentage of salary (in hundredths) | 66.00% |  |
Retirement age (in years) | 67 |  |
Imputed interest rate (in hundredths) | 3.90% | 3.90% |
Chairman, President and CEO [Member] |  |  |
Post Retirement Benefits With Individual Employees [Line Items] |  |  |
Required service period (in years) | 14Y |  |
Maximum benefit as a percentage of salary (in hundredths) | 66.00% |  |
Retirement age (in years) | 70 |  |
Imputed interest rate (in hundredths) | 3.90% | 3.90% |

X
- Definition The imputed interest on benefit plan assets. + References No definition available. + Details
Name: | nat_DeferredCompensationLiabilityImputedInterest
Namespace Prefix: | nat_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The maximum annual benefit as a percentage of salary at the time of retirement. + References No definition available. + Details
Name: | nat_DeferredCompensationLiabilityMaximumBenefitAsPercentageOfSalary
Namespace Prefix: | nat_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The required retirement age of plan participants. + References No definition available. + Details
Name: | nat_DeferredCompensationLiabilityRetirementAge
Namespace Prefix: | nat_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The compensation expense recognized during the period pertaining to the deferred compensation arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64, 65 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 6, 7 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The minimum period that the individual is required to perform services in order to be fully vested under the deferred compensation arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64, 65, A240 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualRequisiteServicePeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration