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COMMITMENTS AND CONTINGENCIES (Details) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 12 Months Ended
Jan. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Claim
Dec. 31, 2012
Claim
Subsequent Event [Line Items]        
Number of claims filed   0us-gaap_LossContingencyPendingClaimsNumber 0us-gaap_LossContingencyPendingClaimsNumber 0us-gaap_LossContingencyPendingClaimsNumber
Gulf Navigation Holding PSJ [Member]        
Subsequent Event [Line Items]        
Period of charter   6 years    
Damages awarded $ 10.2us-gaap_LossContingencyDamagesAwardedValue
/ dei_LegalEntityAxis
= nat_GulfNavigationHoldingPsjMember