Summary of Significant Accounting Policies - Loans Held for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Losses on representations and warranties associated with sale of loans	$ 0	$ 0	$ 0

Losses on issue of representations and warranties associated with sale of loans.

No definition available.

Name:	bsrr_LossesOnIssueOfRepresentationsAndWarrantiesAssociatedWithSaleOfLoans
Namespace Prefix:	bsrr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration