Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Associated Banc-Corp
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 2,848,851	$ 2,706,760
Total Capital Actual Ratio	13.22%	12.68%
Total Capital for Capital Adequacy Purposes Amount	$ 1,723,557	$ 1,707,276
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 Capital Actual Amount	$ 2,331,245	$ 2,191,798
Tier 1 Capital Actual Ratio	10.82%	10.27%
Tier 1 Capital for Adequacy Purposes Amount	$ 1,292,668	$ 1,280,457
Tier 1 Capital for Adequacy Purposes Ratio	6.00%	6.00%
Common Equity Tier One Capital	$ 2,171,508	$ 2,032,587
Common Equity Tier One Capital to Risk Weighted Assets	10.08%	9.52%
Common Equity Tier One Capital Required for Capital Adequacy	$ 969,501	$ 960,343
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier 1 Leverage Capital Actual Amount	$ 2,331,245	$ 2,191,798
Tier 1 Leverage Capital Actual Ratio	8.02%	7.83%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,162,929	$ 1,119,685
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Associated Bank, N.A.
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 2,625,945	$ 2,565,062
Total Capital Actual Ratio	12.24%	12.07%
Total Capital for Capital Adequacy Purposes Amount	$ 1,716,910	$ 1,700,737
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Total Capital to be Well Capitalized Amount	$ 2,146,138	$ 2,125,921
Total Capital to be Well Capitalized Ratio	10.00%	10.00%
Tier 1 Capital Actual Amount	$ 2,357,354	$ 2,298,812
Tier 1 Capital Actual Ratio	10.98%	10.81%
Tier 1 Capital for Adequacy Purposes Amount	$ 1,287,683	$ 1,275,553
Tier 1 Capital for Adequacy Purposes Ratio	6.00%	6.00%
Tier 1 Capital To Be Well Capitalized Amount	$ 1,716,910	$ 1,700,737
Tier 1 Capital To Be Well Capitalized Ratio	8.00%	8.00%
Common Equity Tier One Capital	$ 2,157,354	$ 2,098,812
Common Equity Tier One Capital to Risk Weighted Assets	10.05%	9.87%
Common Equity Tier One Capital Required for Capital Adequacy	$ 965,762	$ 956,664
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	$ 1,394,989	$ 1,381,849
Tier 1 Equity Capital to be Well Capitalized Ratio	6.50%	6.50%
Tier 1 Leverage Capital Actual Amount	$ 2,357,354	$ 2,298,812
Tier 1 Leverage Capital Actual Ratio	8.13%	8.24%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,159,959	$ 1,115,731
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Tier 1 Leverage Capital To Be Well Capitalized Amount	$ 1,449,448	$ 1,394,663
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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Amount of Common Equity Tier 1 Risk-based Capital required to be categorized as well-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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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in 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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The minimum Tier One Capital Ratio (Tier one 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 Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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