Fair Value Measurements, Textuals (Details)		12 Months Ended
Dec. 31, 2020 shares	Dec. 31, 2020 shares
Fair Value Disclosures [Abstract]
Closing Ratio		90.00%
Visa Restricted Shares Owned	77,996
Visa Class A Shares Current Conversion from Class B	126,572	126,572

Represents the percentage of loans currently in a lock position which management estimates will ultimately close.

No definition available.

Name:	asb_FairValueInputsClosingRatio
Namespace Prefix:	asb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration