PARENT COMPANY FINANCIAL INFORMATION (Narrative) (Details) - Parent Company $ in Millions	Dec. 31, 2020 USD ($)
Aggregate amount of unrestricted funds	$ 370.8
Aggregate amount of unrestricted funds percentage	13.69%

Percentage of aggregate amount of unrestricted funds available for transfer to the Parent Company from the Bank to consolidated net assets.

No definition available.

Name:	aub_PercentageOfAggregateAmountOfUnrestrictedFundsAvailableToConsolidatedNetAssets
Namespace Prefix:	aub_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant