Financing Receivable, Nonaccrual, Interest Income String

No definition available.

Name:	asb_FinancingReceivableNonaccrualInterestIncomeString
Namespace Prefix:	asb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans Information

+ References

No definition available.

+ Details

Name:	asb_LoansInformationLineItems
Namespace Prefix:	asb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Restructured Loans Subsequently Accruing

+ References

No definition available.

+ Details

Name:	asb_RestructuredLoansSubsequentlyAccruing
Namespace Prefix:	asb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Ytd Restructured Loans Still On Nonaccrual

+ References

No definition available.

+ Details

Name:	asb_YtdRestructuredLoansStillOnNonaccrual
Namespace Prefix:	asb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ 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 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=asb_PossibleLiquidityIssuesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

Loans Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Loans Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Loans Information [Line Items]
Interest receivable	$ 90,263	$ 91,196
Financing Receivable, Nonaccrual, Interest Income	3 million
Recorded Investment(a)	$ 36,154	15,940	$ 11,429
Restructured Loans Subsequently Accruing	30,000
Ytd Restructured Loans Still On Nonaccrual	6,000
Loans and Leases Receivable, Impaired, Commitment to Lend	11,000
Loans and Finance Receivables [Member]
Loans Information [Line Items]
Interest receivable	66,000	$ 63,000
Possible liquidity issues [Member]
Loans Information [Line Items]
Financing Receivable, Troubled Debt Restructuring	68,000			$ 114,000
Possible liquidity issues [Member] \| Oil and Gas Portfolio Segment [Member]
Loans Information [Line Items]
Financing Receivable, Troubled Debt Restructuring	55,000
Possible liquidity issues [Member] \| Commercial Real Estate Lending [Member]
Loans Information [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 13,000