Credit Quality and Nonperforming Assets - Troubled Debt Restructurings - Tabular Disclosure (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($) item	Sep. 30, 2018 USD ($) item	Sep. 30, 2019 USD ($) item	Sep. 30, 2018 USD ($) item
Financing Receivable, Modifications [Line Items]
Number of Loans	0			0
Pre-Modification Outstanding Recorded Investment	$ 233	$ 124	$ 804	$ 1,304
Post-Modification Outstanding Recorded Investment	233	124	804	1,304
Reserve Difference	(40)	2	(106)	6
Reserve	$ 9	6	13	$ 49
Real Estate Sector [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	0			0
Pre-Modification Outstanding Recorded Investment	$ 0	97	344	$ 964
Post-Modification Outstanding Recorded Investment	0	97	344	964
Reserve Difference	0	0	0	4
Reserve	$ 0	$ 3	$ 1	$ 21
Real Estate Sector [Member] \| Other construction/land [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	0	0	0	0
Reserve Difference	0	0	0	0
Reserve	$ 0	$ 0	$ 0	$ 0
Real Estate Sector [Member] \| 1-4 Family - Closed-End [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	0	0	0	0
Reserve Difference	0	0	0	0
Reserve	$ 0	$ 0	$ 0	$ 0
Real Estate Sector [Member] \| Equity Lines [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	1	2	7
Pre-Modification Outstanding Recorded Investment	$ 0	$ 97	$ 344	$ 964
Post-Modification Outstanding Recorded Investment	0	97	344	964
Reserve Difference	0	0	0	4
Reserve	$ 0	$ 3	$ 1	$ 21
Real Estate Sector [Member] \| Multi-Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	0	0	0	0
Reserve Difference	0	0	0	0
Reserve	$ 0	$ 0	$ 0	$ 0
Real Estate Sector [Member] \| Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	0	0	0	0
Reserve Difference	0	0	0	0
Reserve	$ 0	$ 0	$ 0	$ 0
Real Estate Sector [Member] \| Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	0	0	0	0
Reserve Difference	0	0	0	0
Reserve	$ 0	$ 0	$ 0	$ 0
Agricultural Sector [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	1	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 7	$ 0	$ 7
Post-Modification Outstanding Recorded Investment	0	7	0	7
Reserve Difference	0	2	0	2
Reserve	$ 0	$ 2	$ 0	$ 2
Commercial and Industrial Sector [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	3	1	7	3
Pre-Modification Outstanding Recorded Investment	$ 233	$ 10	$ 401	$ 323
Post-Modification Outstanding Recorded Investment	233	10	401	323
Reserve Difference	(40)	0	(59)	0
Reserve	$ 9	$ 1	$ 10	$ 26
Consumer Loans Sector [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| item	0	1	2	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 10	$ 59	$ 10
Post-Modification Outstanding Recorded Investment	0	10	59	10
Reserve Difference	0	0	(47)	0
Reserve	$ 0	$ 0	$ 2	$ 0

Financing receivable, modifications, number of contracts, during period.

No definition available.

Name:	bsrr_FinancingReceivableModificationsNumberOfContractsDuringPeriod
Namespace Prefix:	bsrr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing receivable modifications reserve.

+ References

No definition available.

+ Details

Name:	bsrr_FinancingReceivableModificationsReserve
Namespace Prefix:	bsrr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Increase decrease in financing receivable modification.

+ References

No definition available.

+ Details

Name:	bsrr_IncreaseDecreaseInFinancingReceivableModification
Namespace Prefix:	bsrr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_RealEstateSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=bsrr_ConstructionAndLandDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=bsrr_OneToFourFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=bsrr_MultiFamilyResidentialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=bsrr_CommercialRealEstateOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=bsrr_FarmlandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_AgriculturalSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_CommercialAndIndustrialSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=bsrr_ConsumerLoansSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: