Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Details Textuals) $ in Millions	Jan. 11, 2016 USD ($) complaint	May 22, 2015 USD ($) branch loan_production_office	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
unfunded commitments			$ 25.0	$ 24.0
Carrying value of investments			85.0	52.0
Commitments under unconsolidated projects			69.0	61.0
Commitment term		3 years
Mortgage loan commitment		$ 196.0
Number of branch opening commitments | branch		1
Number of loan production offices | loan_production_office		4
Conciliation agreement cost, commitment term		4 years
Number of complaints filed under legal proceedings | complaint	2
Loans repurchased under make whole requests			2.0	3.0
Loans sold to outside investors original amount			9,200.0
Loans sold to outside investors remaining outstanding amount			6,100.0
Residential mortgage loans sold with recourse risk			62.0	68.0
Residential mortgage loans sold with credit recourse risk			$ 98.0	$ 132.0
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	$ 6.0
Damages sought, cash	4.0
American Funds Service Company v Associated Bank [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Damages sought	$ 0.6