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Stockholders' Equity (Detail Textuals) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Stockholders Equity [Line Items]      
Retained earnings from which dividends may not be paid without prior approval, total $ 19,729,000 $ 18,752,000 $ 17,171,000
Employee stock purchase benefit plans      
Stockholders Equity [Line Items]      
Employee eligibility period 1 year    
Employees to buy stock under options granted 85.00%    
Options are vested when granted and will expire no later than 27 months    
Common stock, capital shares reserved for future issuance 48,011    
Dividend reinvestment and stock purchase plan      
Stockholders Equity [Line Items]      
Employees to buy stock under options granted 95.00%    
Shares of common stock purchased 13,494 12,397 13,594
Common stock, capital shares reserved for future issuance 171,645    
Stockholder purchase plan      
Stockholders Equity [Line Items]      
Options are vested when granted and will expire no later than 3 months    
Common stock, capital shares reserved for future issuance 313,919