RESTRICTED CASH BALANCES (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
RESTRICTED CASH BALANCES
Average reserve balances maintained with Federal Reserve Bank	$ 1,400,000	$ 1,700,000
Compensating balance required to be maintained at Federal Home Loan Bank of Pittsburgh	0	30,000,000
Compensating balances maintained at correspondent banks	$ 378,000	$ 775,000

Represents the amount of compensating balance, which is required to be maintained at the Federal Home Loan Bank to collateralize a letter of credit, which the bank had pledged to collateralize certain municipal deposits.

No definition available.

Name:	fncb_CompensatingBalanceRequiredToMaintainAtFederalHomeLoanBank
Namespace Prefix:	fncb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant