Cover
| Cover | Jun. 11, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jun. 11, 2020 |
| Current Fiscal Year End Date | --12-31 |
| Entity File Number | 001-31343 |
| Entity Registrant Name | Associated Banc-Corp |
| Entity Central Index Key | 0000007789 |
| Entity Tax Identification Number | 39-1098068 |
| Entity Incorporation, State or Country Code | WI |
| 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 |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | ASB |
| Security Exchange Name | NYSE |
| Series C Preferred Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member] | |
| Entity Information [Line Items] | |
| 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 |
| Trading Symbol | ASB PrC |
| Security Exchange Name | NYSE |
| Series D Preferred Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member] | |
| Entity Information [Line Items] | |
| 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 |
| Trading Symbol | ASB PrD |
| Security Exchange Name | NYSE |
| Series E Preferred Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member] | |
| Entity Information [Line Items] | |
| 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 |
| Trading Symbol | ASB PrE |
| Security Exchange Name | NYSE |