Amount of financing receivable on nonaccrual status with no allowance for credit loss.

Name:	us-gaap_FinancingReceivableNonaccrualNoAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualStatusLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of financing receivable 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5111-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 80
-URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922355-210448

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_CommercialRealEstateOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_CommercialRealEstateNonOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=srt_MultifamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_Residential1To4FamilyCommercialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_Residential1To4FamilyConsumerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_Residential1To4FamilyRevolvingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_AutomobileLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_ConsumerSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=aub_OtherCommercialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LOANS AND ALLOWANCE FOR LOAN LOSSES (Summary of Loans on Nonaccrual Status) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	$ 42,448	$ 45,204	$ 28,232	$ 27,000
Nonaccrual With No Allowance For Credit Losses	11,497
Loans Past Due Over 90 Days Still Accruing	13,634		13,396
Construction and Land Development
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	3,072	4,060	3,703
Nonaccrual With No Allowance For Credit Losses	1,985
Loans Past Due Over 90 Days Still Accruing	0		189
Commercial Real Estate - Owner Occupied
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	7,128	13,889	6,003
Nonaccrual With No Allowance For Credit Losses	1,994
Loans Past Due Over 90 Days Still Accruing	3,727		1,062
Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	2,317	1,368	381
Nonaccrual With No Allowance For Credit Losses	0
Loans Past Due Over 90 Days Still Accruing	148		1,451
Multifamily Real Estate
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	33	0	0
Nonaccrual With No Allowance For Credit Losses	0
Loans Past Due Over 90 Days Still Accruing	0		474
Commercial and Industrial
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	2,107	3,037	1,735
Nonaccrual With No Allowance For Credit Losses	1
Loans Past Due Over 90 Days Still Accruing	1,114		449
Residential 1-4 Family - Commercial
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	9,993	6,492	4,301
Nonaccrual With No Allowance For Credit Losses	6,388
Loans Past Due Over 90 Days Still Accruing	1,560		674
Residential 1-4 Family - Consumer
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	12,600	13,117	9,292
Nonaccrual With No Allowance For Credit Losses	1,069
Loans Past Due Over 90 Days Still Accruing	5,699		4,515
Residential 1-4 Family - Revolving
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	4,629	2,490	2,080
Nonaccrual With No Allowance For Credit Losses	60
Loans Past Due Over 90 Days Still Accruing	826		3,357
Auto
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	500	565	563
Nonaccrual With No Allowance For Credit Losses	0
Loans Past Due Over 90 Days Still Accruing	166		272
Consumer
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	69	88	77
Nonaccrual With No Allowance For Credit Losses	0
Loans Past Due Over 90 Days Still Accruing	394		953
Other Commercial
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	0	$ 98	97
Nonaccrual With No Allowance For Credit Losses	0
Loans Past Due Over 90 Days Still Accruing	$ 0		$ 0