Fair Value Measurements, Textuals (Details)	12 Months Ended
Dec. 31, 2018
Fair Value Disclosures [Abstract]
Closing Ratio	84.00%

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