Other securities and OTTI (Details) (USD $)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Investments, All Other Investments [Abstract]
OTTI equity securities		$ 200,000
Other securities	63,746,000	68,360,000
Amount of stock repurchased at par by Federal Home Loan Bank of Pittsburgh	$ 4,600,000

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

No definition available.

Name:	npbc_OttiOnThreeBankEquitySecurities
Namespace Prefix:	npbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration