Loans, Troubled Debt Restructurings Subsequent Default (Details) $ in Thousands	3 Months Ended
Mar. 31, 2016 USD ($) loan	Mar. 31, 2015 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	16	41
Recorded Investment \| $	$ 1,314	$ 2,391
Commercial real estate — owner occupied
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	1
Recorded Investment \| $	$ 0	$ 297
Real estate construction
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	1	0
Recorded Investment \| $	$ 10	$ 0
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	7	16
Recorded Investment \| $	$ 1,151	$ 1,239
Home Equity Portfolio Segments [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	8	24
Recorded Investment \| $	$ 153	$ 855

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.

No definition available.

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=asb_CommercialRealEstateOwnerOccupiedPortfolioMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=asb_HomeEquityPortFolioSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: