Quarterly report pursuant to Section 13 or 15(d)

Acquisition Activity (Details Textual)

v3.10.0.1
Acquisition Activity (Details Textual) - USD ($)
$ in Thousands
 1 Months Ended 9 Months Ended
Jul. 26, 2018
Jul. 25, 2018
Sep. 30, 2018
Sep. 30, 2017
Mar. 31, 2019
Dec. 31, 2017
Business Acquisition [Line Items]            
Payments to Acquire Businesses, Net of Cash Acquired     $ 8,689 $ 0    
Goodwill     $ 8,170     $ 2,792
Scenario, Forecast [Member]            
Business Acquisition [Line Items]            
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets         $ 1,300,000  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets         839,000  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities         $ 1,100,000  
First Personal Bank [Member]            
Business Acquisition [Line Items]            
Business Acquisition Description Of Consideration Paid     Merger, each First Personal stockholder holding 100 or more shares of First Personal common stock received fixed consideration of (i) 0.1246 shares of NWIN common stock, and (ii) $6.67 per share in cash for each outstanding share of First Personal’s common stock. Stockholders holding less than 100 shares of First Personal common stock received $12.12 in cash and no stock consideration for each outstanding share of First Personal common stock. Any fractional shares of NWIN common stock that a First Personal stockholder would have otherwise received in the First Personal Merger were cashed out in the amount of such fraction multiplied by $42.95.      
Business Combination, Consideration Transferred   $ 15,600        
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares   161,875        
Payments to Acquire Businesses, Net of Cash Acquired $ 8,700 $ 8,700        
Business Combination Financial Information Assets Reported by the Acquiree   138,900        
Business Combination Financial Information Loans Receivables Reported by the Acquiree   98,000        
Business Combination Financial Information Deposits Reported by the Acquiree   $ 125,100        
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets 140,500          
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets 94,600          
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities 130,300          
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities 124,900          
Goodwill 5,400          
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable $ 6,900          
AJS Bancorp Inc [Member]            
Business Acquisition [Line Items]            
Business Acquisition Description Of Consideration Paid     each AJSB stockholder who holds 100 or more shares of AJSB common stock will have the right to receive fixed consideration of (i) 0.2030 shares of NWIN common stock, and (ii) $7.20 per share in cash for each outstanding share of AJSB’s common stock, subject to adjustment as provided in the AJSB Merger Agreement. Stockholders holding less than 100 shares of AJSB common stock will have the right to receive $16.00 in cash and no stock consideration for each outstanding share of AJSB common stock.      
Business Combination Financial Information Assets Reported by the Acquiree     $ 182,900      
Business Combination Financial Information Loans Receivables Reported by the Acquiree     96,800      
Business Combination Financial Information Deposits Reported by the Acquiree     $ 153,500