Restriction on Cash and Due from Banks (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Restriction on Cash and Due from Banks [Abstract]
Reserve funds to be maintained with Federal Reserve Bank	$ 16,100

Amount of reserve funds to be maintained in the form of cash or on deposit with the Federal Reserve Bank.

No definition available.

Name:	bsvn_ReserveFundsToBeMaintainedWithFederalReserveBank
Namespace Prefix:	bsvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant