Shares transferred at acquisition-date in consideration of business combination.

No definition available.

Name:	asb_BusinessCombinationConsiderationSharesTransferred
Namespace Prefix:	asb_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Acquisitions

+ References

No definition available.

+ Details

Name:	asb_NumberofAcquisitions
Namespace Prefix:	asb_
Data Type:	xbrli:integerItemType
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

No definition available.

+ Details

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

- Definition

Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

+ References

No definition available.

+ Details

Name:	us-gaap_FinitelivedIntangibleAssetsAcquired1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=asb_WhitnellMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=asb_BankMutualMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisition (Details Textuals)			3 Months Ended		12 Months Ended
Acquisition (Details Textuals)	Oct. 02, 2017 acquisition	Jul. 20, 2017 acquisition shares	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 acquisition
Business Acquisition [Line Items]
Goodwill acquired during period \| $			$ 4,000,000	$ 55,000
Additions to finite-lived intangible assets \| $			$ 2,000,000	$ 162,000
Number of Acquisitions					2
Whitnell [Member]
Business Acquisition [Line Items]
Number of Acquisitions	1
Bank Mutual [Member]
Business Acquisition [Line Items]
Number of Acquisitions		1
Consideration shares transferred \| shares		0.422