Fair Value Measurements Equity Securities Without Readily Determinable Fair Values (Details) $ in Thousands	3 Months Ended
Mar. 31, 2023 USD ($)
Equity Securities Without Readily Determinable Fair Value Amount [Roll Forward]
Carrying value as of December 31, 2022	$ 19,225
Carrying value changes	0
Purchases	5,003
Equity Securities without Readily Determinable Fair Value, Sales, Annual Amount	0
Carrying value as of March 31, 2023	24,228
Cumulative upward carrying value changes between January 1, 2018 and March 31, 2023	19,134
Cumulative downward carrying value changes/impairment between January 1, 2018 and March 31, 2023	$ 0

Equity Securities without Readily Determinable Fair Value, Additions, Annual Amount

No definition available.

Name:	asb_EquitySecuritiesWithoutReadilyDeterminableFairValueAdditionsAnnualAmount
Namespace Prefix:	asb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Equity Securities Without Readily Determinable Fair Value Amount [Roll Forward]

+ References

No definition available.

+ Details

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

- Definition

Equity Securities without Readily Determinable Fair Value, Sales, Annual Amount

+ References

No definition available.

+ Details

Name:	asb_EquitySecuritiesWithoutReadilyDeterminableFairValueSalesAnnualAmount
Namespace Prefix:	asb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

+ Details

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

- Definition

Amount of cumulative loss from downward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

+ Details

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

- Definition

Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

+ Details

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cumulative gain from upward price adjustment on investment in equity security without readily determinable fair value.

+ References

+ Details

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant