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Stock Based Compensation (Summary of Stock Option Activity) (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Stock-Based Compensation [Abstract]      
Options, Outstanding, beginning of period 206,463us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber    
Options, Granted 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross    
Options, Exercised (5,978)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised    
Options, Forfeited 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod    
Options, Outstanding, end of period 200,485us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 206,463us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Options, Exercisable, end of period 187,985us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber    
Weighted Average Exercise Price Per Share, Outstanding, beginning of period $ 26.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Granted       
Weighted Average Exercise Price Per Share, Exercised $ 25.87us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Forfeited       
Weighted Average Exercise Price Per Share, Outstanding, end of period $ 26.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 26.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Weighted Average Exercise Price Per Share, Exercisable, end of period $ 26.61us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice    
Weighted Average Remaining Contractual Term, Outstanding, beginning of period 5 years 6 months 5 years 8 months 12 days  
Weighted Average Remaining Contractual Term, Exercised During Period 5 years 1 month 6 days    
Weighted Average Remaining Contractual Term, Outstanding, end of period 5 years 6 months 5 years 8 months 12 days  
Weighted Average Remaining Contractual Term, Exercisable at End of Period 5 years 2 months 12 days    
Aggregate Intrinsic Value, Outstanding, beginning of period $ 478us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue    
Aggregate Intrinsic Value, Granted in Period 0nwfl_AggregateIntrinsicValueGrantedInPeriod    
Aggregate Intrinsic Value, Exercised in Period 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue    
Aggregate Intrinsic Value, Forfeited in Period 0nwfl_AggregateIntrinsicValueForfeitedInPeriod    
Aggregate Intrinsic Value, Outstanding, end of period 235us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue 478us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue  
Aggregate Intrinsic Value, Exercisable at end of period 235us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1    
Unrecognized compensation cost related to non-vested options granted $ 50us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions    
Share Price $ 27.69us-gaap_SharePrice $ 29.05us-gaap_SharePrice $ 28.60us-gaap_SharePrice