Investment Securities - Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales and calls	$ 280,780	$ 188,432	$ 413,706	$ 384,763
Gross realized gains	1,565	739	1,818	754
Gross realized losses	$ 98	$ 608	$ 177	$ 972

The cash inflow associated with maturities (principal being due), prepayments and calls (requests of early payments) on securities not classified as either held-to-maturity securities or trading securities which are classified as available-for-sale securities.

No definition available.

Name:	ubsi_ProceedsFromMaturitiesSalesAndCallsOfAvailableForSaleSecurities
Namespace Prefix:	ubsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration