| Document and Entity Information | Sep. 17, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | UNITED BANKSHARES INC/WV |
| Amendment Flag | false |
| Entity Central Index Key | 0000729986 |
| Document Type | 8-K |
| Document Period End Date | Sep. 17, 2020 |
| Entity Incorporation State Country Code | WV |
| Entity File Number | 002-86947 |
| Entity Tax Identification Number | 55-0641179 |
| Entity Address, Address Line One | 300 United Center |
| Entity Address, Address Line Two | 500 Virginia Street |
| Entity Address, Address Line Three | East |
| Entity Address, City or Town | Charleston |
| Entity Address, State or Province | WV |
| Entity Address, Postal Zip Code | 25301 |
| City Area Code | (304) |
| Local Phone Number | 424-8800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $2.50 per share |
| Trading Symbol | UBSI |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
