Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Associated Banc-Corp
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 3,216,575	$ 2,848,851
Total Capital Actual Ratio	13.47%	13.22%
Total Capital for Capital Adequacy Purposes Amount	$ 1,910,022	$ 1,723,557
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 Capital Actual Amount	$ 2,705,939	$ 2,331,245
Tier 1 Capital Actual Ratio	11.33%	10.82%
Tier 1 Capital for Adequacy Purposes Amount	$ 1,432,517	$ 1,292,668
Tier 1 Capital for Adequacy Purposes Ratio	6.00%	6.00%
Common Equity Tier One Capital	$ 2,449,721	$ 2,171,508
Common Equity Tier One Capital to Risk Weighted Assets	10.26%	10.08%
Common Equity Tier One Capital Required for Capital Adequacy	$ 1,074,388	$ 969,501
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier 1 Leverage Capital Actual Amount	$ 2,705,939	$ 2,331,245
Tier 1 Leverage Capital Actual Ratio	8.48%	8.02%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,276,624	$ 1,162,929
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Associated Bank, N.A.
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 2,909,064	$ 2,625,945
Total Capital Actual Ratio	12.23%	12.24%
Total Capital for Capital Adequacy Purposes Amount	$ 1,903,155	$ 1,716,910
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Total Capital to be Well Capitalized Amount	$ 2,378,944	$ 2,146,138
Total Capital to be Well Capitalized Ratio	10.00%	10.00%
Tier 1 Capital Actual Amount	$ 2,646,705	$ 2,357,354
Tier 1 Capital Actual Ratio	11.13%	10.98%
Tier 1 Capital for Adequacy Purposes Amount	$ 1,427,367	$ 1,287,683
Tier 1 Capital for Adequacy Purposes Ratio	6.00%	6.00%
Tier 1 Capital To Be Well Capitalized Amount	$ 1,903,155	$ 1,716,910
Tier 1 Capital To Be Well Capitalized Ratio	8.00%	8.00%
Common Equity Tier One Capital	$ 2,446,782	$ 2,157,354
Common Equity Tier One Capital to Risk Weighted Assets	10.29%	10.05%
Common Equity Tier One Capital Required for Capital Adequacy	$ 1,070,525	$ 965,762
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier 1 Equity Capital to be Well Capitalized Amount	$ 1,546,314	$ 1,394,989
Tier 1 Equity Capital to be Well Capitalized Ratio	6.50%	6.50%
Tier 1 Leverage Capital Actual Amount	$ 2,646,705	$ 2,357,354
Tier 1 Leverage Capital Actual Ratio	8.31%	8.13%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,274,380	$ 1,159,959
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Tier 1 Leverage Capital To Be Well Capitalized Amount	$ 1,592,976	$ 1,449,948
Tier 1 Leverage Capital To Be Well Capitalized Ratio	5.00%	5.00%

Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets

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Common Equity Tier One Capital Required to be Well Capitalized to Risk Weighted Assets

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Common Equity Tier One Capital to Risk Weighted Assets

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Amount of Common Equity Tier One Risk-based Capital, as defined by regulatory framework.

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Amount of Common Equity Tier 1 Risk-based Capital required to be categorized as adequately capitalized under regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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