Collateral securities maintain to cover potential workers compensation claims losses.

No definition available.

Name:	bbsi_CollateralSecuritiesMaintainToCoverPotentialWorkersCompensationClaimsLosses
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Description of renewed agreement.

+ References

No definition available.

+ Details

Name:	bbsi_DescriptionOfRenewedAgreement
Namespace Prefix:	bbsi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Insurance deposit as security for future payment obligations under workers compensation program.

+ References

No definition available.

+ Details

Name:	bbsi_InsuranceDepositAsSecurityForFuturePaymentObligationsUnderWorkersCompensationProgram
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maximum additional premium charged amount, if claims develop adversely.

+ References

No definition available.

+ Details

Name:	bbsi_MaximumAdditionalPremiumChargedAmountIfClaimsDevelopAdversely
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Maximum savings amount, if claims develop favorably.

+ References

No definition available.

+ Details

Name:	bbsi_MaximumSavingsAmountIfClaimsDevelopFavorably
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of worker's compensation exposure covered.

+ References

No definition available.

+ Details

Name:	bbsi_PercentageOfWorkersCompensationExposureCovered
Namespace Prefix:	bbsi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Reinsurance coverage per occurrence.

+ References

No definition available.

+ Details

Name:	bbsi_ReinsuranceCoveragePerOccurrence
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Standby letters of credit and a surety bond.

+ References

No definition available.

+ Details

Name:	bbsi_StandbyLettersOfCreditAndSuretyBond
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Workers compensation accrual for costs incurred in excess of retention limits offset by receivable.

+ References

No definition available.

+ Details

Name:	bbsi_WorkersCompensationAccrualForCostsIncurredInExcessOfRetentionLimitsOffsetByReceivable
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Workers compensation claims coverage per occurrence.

+ References

No definition available.

+ Details

Name:	bbsi_WorkersCompensationClaimsCoveragePerOccurrence
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Workers compensation claims incurred but not reported in excess of retention limits.

+ References

No definition available.

+ Details

Name:	bbsi_WorkersCompensationClaimsIncurredButNotReportedInExcessOfRetentionLimits
Namespace Prefix:	bbsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Workers compensation claims maximum coverage per occurrence.

+ References

No definition available.

+ Details

Name:	bbsi_WorkersCompensationClaimsMaximumCoveragePerOccurrence
Namespace Prefix:	bbsi_
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

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

- Definition

Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ Details

Name:	us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=bbsi_TwoThousandTwentyOneToTwoThousandTwentyTwoPolicyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=bbsi_TwoThousandTwentyTwoToTwoThousandTwentyThreePolicyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=bbsi_TwoThousandTwentyThreeToTwoThousandTwentyFourPolicyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=bbsi_TwoThousandTwentyFourToTwoThousandTwentyFivePolicyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=bbsi_SelfInsuredProgramsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_MD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_CO
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=bbsi_InsuredProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Workers' Compensation Claims Liabilities - Additional Information (Detail) - USD ($)			6 Months Ended		12 Months Ended	48 Months Ended
	Jul. 01, 2021	Jun. 29, 2020	Jun. 30, 2025	Jun. 30, 2020	Dec. 31, 2024	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Description of renewed agreement						Effective July 1, 2021, the Company entered into a fully insured arrangement for its insured program, whereby third-party insurers assume substantially all risk of loss for claims incurred under the program. This fully insured arrangement has been extended annually and covers claims incurred between July 1, 2021 and June 30, 2026.
Balance in Chubb trust accounts			$ 153,900,000		$ 197,100,000	$ 153,900,000
Workers compensation liability			113,902,000		128,446,000	113,902,000	$ 121,228,000	$ 149,630,000	$ 158,054,000	$ 167,763,000
Collateral securities maintain to cover potential workers compensation claims losses			52,100,000		55,900,000	52,100,000
Surety bonds and standby letters of credit			52,100,000			52,100,000
Reserves and IBNR in excess of retention limits incurred but not reported			5,900,000		6,000,000.0
Other Assets [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accrual for costs incurred in excess of retention limits offset by a receivable			5,900,000		$ 6,000,000	5,900,000
2021-2022 Policy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum additional premium charged amount for twelve month policy period, if claims develop adversely			7,500,000
2021-2022 Policy [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			20,000,000
2021-2022 Policy [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			30,000,000
2022-2023 Policy [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			20,000,000
2022-2023 Policy [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			30,000,000
2023-2024 Policy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum additional premium charged amount for twelve month policy period, if claims develop adversely			0
2023-2024 Policy [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			20,000,000
2023-2024 Policy [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			30,000,000
2024-2025 Policy [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			20,000,000
2024-2025 Policy [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably			$ 30,000,000
Self Insured Programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of worker's compensation exposure covered			14.00%
Worker's compensation risk claim maximum			$ 3,000,000.0	$ 5,000,000.0
Self Insured Programs [Member] \| Maryland [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reinsurance coverage			1,000,000.0	1,000,000.0		1,000,000.0
Self Insured Programs [Member] \| Colorado [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reinsurance coverage			$ 2,000,000.0	$ 2,000,000.0		$ 2,000,000.0
Insured Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of worker's compensation exposure covered			86.00%
Worker's compensation risk claim maximum	$ 3,000,000
Worker's compensation risk claim maximum		$ 5,000,000