Loans, Allowance for Loan Losses, and Credit Quality (Details Textuals) (USD $) In Millions	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Loans Allowance for Loan Losses and Credit Quality Disclosure (Textuals) [Abstract]
Write down on installment loans transferred to held for sale	$ 10
Number of days of loan due	90 days or more
Interest income recognized on accruing restructured loans	$ 2.6	$ 4.0

Name:

asbc_LoansAllowanceForLoanLossesAndCreditQualityDisclosureTextualsAbstract

Namespace Prefix:

asbc

Data Type:

xbrli:stringItemType

Balance Type:

na

Period Type:

duration