| Document and Entity Information | Apr. 27, 2021$ / shares |
| Registrant CIK | 0000007789 |
| Registrant Name | Associated Banc-Corp |
| SEC Form | 8-K |
| Period End date | Apr. 27, 2021 |
| Tax Identification Number (TIN) | 39-1098068 |
| Emerging Growth Company | false |
| Entity Incorporation, State or Country Code | WI |
| Entity File Number | 001-31343 |
| Entity Address, Address Line One | 433 Main Street |
| Entity Address, City or Town | Green Bay |
| Entity Address, State or Province | WI |
| Entity Address, Postal Zip Code | 54301 |
| City Area Code | 920 |
| Local Phone Number | 491-7500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Amendment Flag | false |
| Common Class A | |
| Trading Symbol | ASB |
| Trading Exchange | NYSE |
| Title of 12(b) Security | Common Stock, Par Value $0.01 per share |
| Entity Listing, Par Value Per Share | $ 0.01 |
| Series C Preferred Stock | |
| Trading Symbol | ASB PrC |
| Trading Exchange | NYSE |
| Title of 12(b) Security | Depositary Shrs, each representing 1/40th intrst in a shr of 6.125% Non-Cum Perp Pref Stock, Srs C |
| Series D Preferred Stock | |
| Trading Symbol | ASB PrD |
| Trading Exchange | NYSE |
| Title of 12(b) Security | Depositary Shrs, each representing 1/40th intrst in a shr of 5.375% Non-Cum Perp Pref Stock Srs D |
| Series E Preferred Stock | |
| Trading Symbol | ASB PrE |
| Trading Exchange | NYSE |
| Title of 12(b) Security | Depositary Shrs, each representing 1/40th intrst in a shr of 5.875% Non-Cum Perp Pref Stock Srs E |
| Series F Preferred Stock | |
| Trading Symbol | ASB PrF |
| Trading Exchange | NYSE |
| Title of 12(b) Security | Depositary Shrs, each representing 1/40th intrst in a shr of 5.625% Non-Cum Perp Pref Stock Srs F |
