Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Oct. 18, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Title of 12(b) Security Common Stock, par value $.01 per share  
Trading Symbol NOV  
Security Exchange Name NYSE  
Entity Central Index Key 0001021860  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Common Stock, Shares Outstanding   385,832,119
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity File Number 1-12317  
Entity Tax Identification Number 76-0475815  
Entity Address, Address Line One 7909 Parkwood Circle Drive  
Entity Address, City or Town Houston  
Entity Address, State or Province TX  
Entity Incorporation, State or Country Code DE  
Entity Address, Postal Zip Code 77036-6565  
City Area Code 713  
Local Phone Number 346-7500  
Document Quarterly Report true  
Document Transition Report false