Derivative and Hedging Activities, Derivative Instruments Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Fair Value	$ 29,391	$ 33,023
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Interest rate lock commitments (mortgage) [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	271,530	126,379
Fair Value	958	1,947
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Forward commitments (mortgage) [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	231,798
Fair Value	403
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Purchased options (time deposit) [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	104,582	110,347
Fair Value	2,715	6,054
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member] \| Forward commitments (mortgage) [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount		234,500
Fair Value		(2,435)
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member] \| Written options (time deposit) [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	104,582	110,347
Fair Value	(2,715)	(6,054)
Not Designated as Hedging Instrument [Member] \| Trading Assets [Member] \| Interest Rate-related instruments - customer and mirror [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	1,665,965	1,636,480
Fair Value	$ 29,391	$ 33,023
Receive Rate	1.56%	1.60%
Pay Rate	1.56%	1.60%
Maturity	41 months	42 months
Not Designated as Hedging Instrument [Member] \| Trading Assets [Member] \| Foreign currency exchange forwards [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	$ 72,976	$ 60,742
Fair Value	1,532	2,140
Not Designated as Hedging Instrument [Member] \| Trading Assets [Member] \| Commodity contract [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	44,380
Fair Value	1,269
Not Designated as Hedging Instrument [Member] \| Trading Liabilities [Member] \| Interest Rate-related instruments - customer and mirror [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	1,665,965	1,636,480
Fair Value	$ (30,886)	$ (35,372)
Receive Rate	1.56%	1.60%
Pay Rate	1.56%	1.60%
Maturity	41 months	42 months
Not Designated as Hedging Instrument [Member] \| Trading Liabilities [Member] \| Foreign currency exchange forwards [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	$ 65,649	$ 56,573
Fair Value	(1,398)	$ (1,957)
Not Designated as Hedging Instrument [Member] \| Trading Liabilities [Member] \| Commodity contract [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	44,256
Fair Value	$ (1,146)

Derivative Average Pay Interest Rate.

No definition available.

Name:	asb_DerivativeAveragePayInterestRate
Namespace Prefix:	asb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Derivative average receive interest rate.

+ References

No definition available.

+ Details

Name:	asb_DerivativeAverageReceiveInterestRate
Namespace Prefix:	asb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAverageRemainingMaturity1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Net fair value of all derivative instruments not designated as a hedging instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13495-108611

+ Details

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

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateLockCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=asb_PurchasedOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=asb_WrittenOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=asb_TradingAssetsrMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=asb_InterestRateRelatedInstrumentsCustomerAndMirrorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=asb_Tradingliabilities1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: