| Parent Company Only Statements (Tables)
 | 12 Months Ended | 
| Dec. 31, 2018 | 
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| Condensed Financial Information Disclosure [Abstract] |  | 
| Condensed Balance Sheet [Table Text Block] | 
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|  |  | NorthWest Indiana Bancorp |  |  
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| Cash on deposit with Peoples Bank |  |  |  |  |  |  |  |  |  
| Investment in Peoples Bank |  |  |  |  |  |  |  |  |  
| Investment in NWIN Risk Management, Inc |  |  |  |  |  |  |  |  |  
| Dividends receivable from Peoples Bank |  |  |  |  |  |  |  |  |  
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| Liabilities and stockholders’ equity |  |  |  |  |  |  |  |  |  
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| Additional paid in capital |  |  |  |  |  |  |  |  |  
| Accumulated other comprehensive (loss) income |  |  |  |  |  |  |  |  |  
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| Total stockholders’ equity |  |  |  |  |  |  |  |  |  
| Total liabilities and stockholders’ equity |  |  |  |  |  |  |  |  |  | 
| Condensed Income Statement [Table Text Block] | 
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|  |  | NorthWest Indiana Bancorp |  |  
|  |  | Condensed Statements of Income |  |  
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| Dividends from Peoples Bank |  |  |  |  |  |  |  |  |  
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| Income before income taxes and equity in undistributed income of Peoples Bank |  |  |  |  |  |  |  |  |  
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| Income before equity in undistributed income of Peoples Bank |  |  |  |  |  |  |  |  |  
| Equity in undistributed  (distributions in excess of income) income of Peoples Bank |  |  |  |  |  |  |  |  |  
| income of NWIN Risk Management, Inc |  |  |  |  |  |  |  |  |  
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| Condensed Cash Flow Statement [Table Text Block] | 
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|  |  | NorthWest Indiana Bancorp |  |  
|  |  | Condensed Statements of Cash Flows |  |  
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| Cash flows from operating activities: |  |  |  |  |  |  |  |  |  
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Adjustments to reconcile  net income to net cash provided by operating activities |  |  |  |  |  |  |  |  |  
| Distributions in excess of income (equity in undistributed income): |  |  |  |  |  |  |  |  |  
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| NWIN Risk Management, Inc |  |  |  |  |  |  |  |  |  
| Stock based compensation expense |  |  |  |  |  |  |  |  |  
| Net surrender value of restricted stock awards |  |  |  |  |  |  |  |  |  
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| Change in other liabilities |  |  |  |  |  |  |  |  |  
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| Net cash - operating activities |  |  |  |  |  |  |  |  |  
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| Cash flows from investing activities: |  |  |  |  |  |  |  |  |  
| Cash paid for acquisition |  |  |  |  |  |  |  |  |  
| Investment in NWIN Risk Management, Inc |  |  |  |  |  |  |  |  |  
| Net cash - investing activities |  |  |  |  |  |  |  |  |  
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| Cash flows from financing activities: |  |  |  |  |  |  |  |  |  
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| Proceeds from issuance of common stock |  |  |  |  |  |  |  |  |  
| Net cash - financing activities |  |  |  |  |  |  |  |  |  
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| Cash at beginning of year |  |  |  |  |  |  |  |  |  
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