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

No definition available.

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Data Type:	xbrli:sharesItemType
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Period Type:	duration

- Definition

Number of Acquisitions

+ References

No definition available.

+ Details

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Namespace Prefix:	asb_
Data Type:	xbrli:integerItemType
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- 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

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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

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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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Balance Type:	debit
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- Details

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- Details

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- Details

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Acquisitions (Details Textuals)			3 Months Ended
Acquisitions (Details Textuals)	Oct. 02, 2017 acquisition	Jul. 20, 2017 acquisition shares	Mar. 31, 2017 USD ($) acquisition	Mar. 31, 2016 USD ($) acquisition
Business Acquisition [Line Items]
Goodwill acquired during period \| $			$ 55,000	$ 3,000,000
Additions to finite-lived intangible assets \| $			$ 162,000	$ 1,000,000
Number of acquisitions			1	2
Bank Mutual
Business Acquisition [Line Items]
Number of acquisitions		1
Consideration shares transferred \| shares		0.422
Subsequent Event \| Whitnell
Business Acquisition [Line Items]
Number of acquisitions	1