XML 136 R122.htm IDEA: XBRL DOCUMENT v3.3.1.900
Note 20 - Subordinated Debentures (Details) - Business Trusts - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Subordinated Borrowing [Line Items]    
Preferred securities outstanding $ 53,100 $ 52,400
Mercantile Bank Capital Trust I [Member]    
Subordinated Borrowing [Line Items]    
Preferred securities outstanding $ 32,000,000  
Mercantile Bank Capital Trust I [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Subordinated Borrowing [Line Items]    
Interest Rate Margin 2.18%  
Firstbank Capital Trust I [Member]    
Subordinated Borrowing [Line Items]    
Preferred securities outstanding $ 10,000,000  
Firstbank Capital Trust I [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Subordinated Borrowing [Line Items]    
Interest Rate Margin 1.99%  
Firstbank Capital Trust II [Member]    
Subordinated Borrowing [Line Items]    
Preferred securities outstanding $ 10,000,000  
Firstbank Capital Trust II [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Subordinated Borrowing [Line Items]    
Interest Rate Margin 1.27%  
Firstbank Capital Trust III [Member]    
Subordinated Borrowing [Line Items]    
Preferred securities outstanding $ 7,500,000  
Firstbank Capital Trust III [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Subordinated Borrowing [Line Items]    
Interest Rate Margin 1.35%  
Firstbank Capital Trust IV [Member]    
Subordinated Borrowing [Line Items]    
Preferred securities outstanding $ 7,500,000  
Firstbank Capital Trust IV [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Subordinated Borrowing [Line Items]    
Interest Rate Margin 1.35%