Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Details Textuals) $ in Thousands	Jan. 11, 2016 USD ($)	May. 22, 2015 USD ($) loan_production_office branch	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Carrying value of investments			$ 52,000	$ 27,000
Commitments under unconsolidated projects			61,000	28,000
Commitment term		3 years
Mortgage loan commitment		$ 196,000
Number of branch opening commitments | branch		1
Number of loan production offices | loan_production_office		4
Conciliation agreement cost, commitment term		4 years
Loans repurchased under make whole requests			3,000	5,000
Loss reimbursement claims under make whole requests			133	734
Loans sold to outside investors original amount			19,900,000
Loans sold to outside investors remaining outstanding amount			7,500,000
Residential mortgage loans sold with recourse risk			68,000	46,000
Residential mortgage loans sold with credit recourse risk			132,000	178,000
Subsequent Event [Member] | The Official Committee of Unsecured Creditors of World Marketing Chicago LLC v Associated Bank [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Damages sought	$ 6,000
Damages sought, cash	4,000
Damages sought, indebtedness	1,000
Subsequent Event [Member] | American Funds Service Company v Associated Bank [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Damages sought	$ 600
Reserve for Off-balance Sheet Activities [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Valuation allowance balance			24,400	24,900	$ 21,900	$ 21,800
Mortgage Repurchase Reserve [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Valuation allowance balance			$ 1,197	$ 3,258	$ 5,737