Loans, Modifications (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Weighted Average Term, Range, From	254 months	334 months
Financing Receivable, Modified, Weighted Average Term, Range, To	407 months	360 months
Interest Rate Below Market Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 739	$ 637
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	(9.00%)	(17.00%)
Extended Maturity [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 0	$ 209
Financing Receivable, Modified, Weighted Average Term Increase from Modification	153 months	26 months
Extended Maturity and Interest Rate Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 674	$ 258
Commercial and Industrial Sector \| Interest Rate Below Market Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 159	$ 47
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	(16.00%)	(16.00%)
Automobile Loan \| Interest Rate Below Market Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 46	$ 61
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	(9.00%)	(2.00%)
Residential mortgage \| Interest Rate Below Market Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	3.00%	0.00%
Residential mortgage \| Extended Maturity [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 0	$ 209
Financing Receivable, Modified, Weighted Average Term Increase from Modification	158 months	26 months
Residential mortgage \| Extended Maturity and Interest Rate Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 643	$ 165
Home equity \| Interest Rate Below Market Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 0	$ 31
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	(3.00%)	1.00%
Home equity \| Extended Maturity [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Weighted Average Term Increase from Modification	64 months	0 months
Home equity \| Extended Maturity and Interest Rate Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 31	$ 93
Other consumer \| Interest Rate Below Market Reduction [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified in Period, Amount	$ 534	$ 498
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	(21.00%)	(20.00%)

Financing Receivable, Modified, Weighted Average Term, Range, From

No definition available.

Name:	asb_FinancingReceivableModifiedWeightedAverageTermRangeFrom
Namespace Prefix:	asb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing Receivable, Modified, Weighted Average Term, Range, To

+ References

No definition available.

+ Details

Name:	asb_FinancingReceivableModifiedWeightedAverageTermRangeTo
Namespace Prefix:	asb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-33

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-34

+ Details

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

- Definition

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

+ Details

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

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_InterestRateBelowMarketReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityAndInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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