Loans Receivable and the Allowance for Credit Losses - Troubled Debt Restructuring (Details) - loan	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Loans Receivable and the Allowance for Credit Losses
Number of loans modified that were deemed troubled debt restructuring	0	0

Number of loans modified that were deemed troubled debt restructuring.

No definition available.

Name:	necb_NumberOfLoansModifiedThatWereDeemedTroubledDebtRestructuring
Namespace Prefix:	necb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration