Fair Value Measurements, Textuals (Details) - shares	3 Months Ended	12 Months Ended
Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Closing Ratio			86.00%
Visa Restricted Shares Owned	77,000	77,000
Visa Class A Shares Current Conversion from Class B	124,956		124,956

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