Borrowed Funds and Debt Obligations - Notes Payable (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2014
Sep. 30, 2015
Debt Instrument [Line Items]    
Notes payable $ 10,250 $ 0
Secured debt    
Debt Instrument [Line Items]    
Notes payable 10,250  
Subordinated debt | London Interbank Offered Rate (LIBOR)    
Debt Instrument [Line Items]    
Notes payable $ 10,000 0
Interest due, rate 2.95%  
Interest rate at period end 3.19%  
Equity securities | Secured debt | London Interbank Offered Rate (LIBOR)    
Debt Instrument [Line Items]    
Notes payable $ 250 $ 0
Interest due, rate 2.95%  
100% of Centrue Bank Stock pledged 100.00%  
Equity securities | Secured debt | Floor    
Debt Instrument [Line Items]    
Interest due, rate 6.50%