| Document and Entity Information | May 01, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | UNITED BANKSHARES INC/WV |
| Amendment Flag | true |
| Entity Central Index Key | 0000729986 |
| Document Type | 8-K/A |
| Document Period End Date | May 1, 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 |
| Amendment Description | This current report on Form 8-K/A is filed as an amendment to the current report on Form 8-K of United Bankshares, Inc. (“United”) filed with the Securities and Exchange Commission (the “SEC”) on May 1, 2020 (the “Initial Report”) relating to United’s acquisition of Carolina Financial Corporation (“Carolina Financial”). This current report is filed to provide, and amends the Initial Report to include, additional acquisition information under Item 2.01 and the pro forma financial information required by Item 9.01(b) of Form 8-K. The pro forma information is included as an exhibit pursuant to Item 9.01(d) of Form 8-K. |
