| Document And Entity Information | Oct. 28, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 28, 2019 |
| Entity Registrant Name | NATIONAL OILWELL VARCO INC |
| Entity Central Index Key | 0001021860 |
| Entity Emerging Growth Company | false |
| Entity File Number | 1-12317 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 76-0475815 |
| Entity Address, Address Line One | 7909 Parkwood Circle Dr. |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77036 |
| City Area Code | 713 |
| Local Phone Number | 346-7500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $.01 per share |
| Trading Symbol | NOV |
| Security Exchange Name | NYSE |
