XML 78 R53.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) |  |  | 12 Months Ended
--- | --- | --- | ---
Apr. 30, 2019 USD ($) | Dec. 31, 2005 item | Dec. 31, 2019 USD ($) item | Dec. 31, 2018 USD ($)
Accounting Policies [Line Items] |  |  |  |
Number of bank branches | item |  |  | 149 |
Number of ATM's | item |  |  | 170 |
Number of business acquisitions | item |  | 2 |  |
Accruals for uncertain tax positions |  |  | $ 0 | $ 0
Impairment charges for goodwill or intangible assets | $ 0 |  | 0 |
Goodwill |  |  | $ 935,560,000 | $ 727,168,000
Commercial loans on nonaccrual status, period |  |  | 90 days |
Number of days past due to charge-off real estate secured loans |  |  | 180 days |
Federal Home Loan Bank requires Bank to maintain percentage of stock equal to outstanding borrowings |  |  | 4.25% | 4.25%
Percentage of Federal Reserve Bank of Richmond reserve |  |  | 6.00% | 6.00%
Future payments, contractual term |  |  | 6 months |
Period of independent appraisal or valuation |  |  | 12 months |
Liabilities for post retirement benefits payable to other beneficiaries |  |  | $ 12,100,000 | $ 10,500,000
Minimum |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Intangible assets, amortization period (years) |  |  | 4 years |
Period past due to change TDR status |  |  | 30 days |
Estimated useful life of bank premises |  |  | 3 years |
Percentage of fair value of the derivative instruments for the hedge to be highly effective |  |  | 80.00% |
Tax position benefit recognition threshold |  |  | 50.00% |
Maximum |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Intangible assets, amortization period (years) |  |  | 10 years |
Period past due to charge off consumer loans non-real estate secured |  |  | 120 days |
Estimated useful life of bank premises |  |  | 50 years |
Percentage of fair value of the derivative instruments for the hedge to be highly effective |  |  | 125.00% |

X
- Definition [Line Items] for Accounting Policies [Table] + References No definition available. + Details
Name: | aub_AccountingPoliciesLineItems
Namespace Prefix: | aub_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Federal home loan bank requires bank to maintain percentage of stock equal to outstanding borrowings. + References No definition available. + Details
Name: | aub_FederalHomeLoanBankRequiresBankToMaintainPercentageOfStockEqualToOutstandingBorrowings
Namespace Prefix: | aub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of ATMs + References No definition available. + Details
Name: | aub_NumberOfAtms
Namespace Prefix: | aub_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of bank branches. + References No definition available. + Details
Name: | aub_NumberOfBankBranches
Namespace Prefix: | aub_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of Business Acquisitions. + References No definition available. + Details
Name: | aub_NumberOfBusinessAcquisitions
Namespace Prefix: | aub_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of days past due to charge-off real estate secured loans. + References No definition available. + Details
Name: | aub_NumberOfDaysPastDueToChargeOffRealEstateSecuredLoans
Namespace Prefix: | aub_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of fair value of the derivative instruments for the hedge to be highly effective. + References No definition available. + Details
Name: | aub_PercentageOfFairValueOfDerivativeInstrumentForHedgeToBeHighlyEffective
Namespace Prefix: | aub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Of Independent Appraisal or Valuation. + References No definition available. + Details
Name: | aub_PeriodOfIndependentAppraisalOrValuation
Namespace Prefix: | aub_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Past Due to Change TDR Status + References No definition available. + Details
Name: | aub_PeriodPastDueToChangeTdrStatus
Namespace Prefix: | aub_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period past due to charge off consumer loans. + References No definition available. + Details
Name: | aub_PeriodPastDueToChargeOffConsumerLoans
Namespace Prefix: | aub_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period past due to consider for placing commercial loans on nonaccrual status. + References No definition available. + Details
Name: | aub_PeriodPastDueToConsiderForPlacingCommercialLoansOnNonaccrualStatus
Namespace Prefix: | aub_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Required percentage of common stock investment percentage to outstanding capital. + References No definition available. + Details
Name: | aub_RequiredPercentageOfCommonStockInvestmentPercentageToOutstandingCapital
Namespace Prefix: | aub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Specified consecutive period of payment of contractual amounts as indicator to determine future payments. + References No definition available. + Details
Name: | aub_SpecifiedConsecutivePeriodOfPaymentOfContractualAmountsAsIndicatorToDetermineFuturePayments
Namespace Prefix: | aub_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax Position Benefit Recognition Threshold + References No definition available. + Details
Name: | aub_TaxPositionBenefitRecognitionThreshold
Namespace Prefix: | aub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
Name: | us-gaap_Goodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13854-109267 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266 + Details
Name: | us-gaap_GoodwillImpairmentLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount recognized for uncertainty in income taxes classified as current. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LiabilityForUncertainTaxPositionsCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of liability for retirement benefits, classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(15)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(15)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_OtherPostretirementBenefitsPayableCurrentAndNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |