Note 19 - Leases (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($)
Lessee, Operating Lease, Early Termination Fee	$ 150

Amounts of early termination under operating lease.

No definition available.

Name:	nksh_LesseeOperatingLeaseEarlyTerminationFee
Namespace Prefix:	nksh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration