Debt Instrument Call Date Earliest Month Year

No definition available.

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- Definition

Debt Instrument, Issuance Date Month, Year

+ References

No definition available.

+ Details

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- Definition

Debt Instrument, Maturity Date Month, Year

+ References

No definition available.

+ Details

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- Definition

Debt Instrument, Option to Purchase, Month Year

+ References

No definition available.

+ Details

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- Definition

Debt Instrument, Option to Purchase Price

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Junior subordinated debentures issued.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

New Senior Debt Issued

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value of securities purchased under agreements to resell and deposits paid for securities borrowed.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.3)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Period Type:	instant

- 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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Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, 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_DebtInstrumentTerm
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Balance Type:	na
Period Type:	duration

- Definition

Stated interest rate of the subordinated debt.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	duration

- Details

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- Details

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- Details

Name:	us-gaap_SubordinatedBorrowingAxis=asb_TwoThousandFourteenSubordinatedNotesMember
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Short and Long-Term Funding (Long-term Funding Narrative) (Details) - USD ($) $ in Millions			1 Months Ended	12 Months Ended
	Aug. 13, 2018	Nov. 13, 2014	Nov. 30, 2014	Dec. 31, 2019	Mar. 31, 2020
Long-Term Funding
Carrying Value of Securities Purchased under Agreements to Resell and Deposits Paid for Securities Borrowed					$ 202.0
Two Thousand Eighteen Senior Notes [Member] [Domain]
Long-Term Funding
Debt Instrument, Issuance Date Month, Year	August 2018
New Senior Debt Issued	$ 300.0
Debt Instrument, Maturity Date Month, Year	August 2021
Debt Instrument Call Date Earliest Month Year	July 2021
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Finance Leases [Member]
Long-Term Funding
Debt Instrument, Term				40 years
Debt Instrument, Maturity Date Month, Year				August 2059
Debt Instrument, Interest Rate, Stated Percentage				3.99%
Debt Instrument, Option to Purchase, Month Year				August 2022
Debt Instrument, Option to Purchase Price				$ 1.2
Two Thousand Fourteen Subordinated Notes
Long-Term Funding
Debt Instrument, Issuance Date Month, Year		November 2014
Junior Subordinated Debentures Issued			$ 250.0
Debt Instrument, Term			10 years
Debt Instrument, Maturity Date Month, Year		January 2025
Debt Instrument Call Date Earliest Month Year		October 2024
Subordinated Borrowing, Interest Rate			4.25%