Workers' Compensation Claims - Additional Information (Detail) - USD ($)				3 Months Ended	6 Months Ended	12 Months Ended
	Jul. 01, 2022	Jul. 01, 2021	Jun. 29, 2020	Mar. 31, 2023	Jun. 30, 2020	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Description of renewed agreement				The Company entered into a new arrangement for its insured program effective July 1, 2021 whereby third-party insurers assumed all risk of loss for claims incurred from July 1, 2021 to June 30, 2022 (the “2021-2022 Policy”). The 2021-2022 Policy allows for premium adjustments depending on overall policy performance. If claims develop favorably, BBSI can participate in the savings up to $20.0 million for the twelve-month policy period. If claims develop adversely, additional premium may be charged up to $7.5 million for the twelve-month policy period.
Maximum savings amount for twelve month policy period, if claims develop favorably				$ 20,000,000.0
Maximum additional premium charged amount for twelve month policy period, if claims develop adversely				7,500,000
Balance in Chubb trust accounts			$ 115,700,000	178,800,000		$ 188,200,000
Workers compensation liability				201,641,000		215,987,000	$ 262,646,000	$ 279,407,000
Collateral securities maintain to cover potential workers compensation claims losses				53,900,000		54,500,000
Surety bonds and standby letters of credit				53,900,000
Reserves incurred in excess of retention limits				3,000,000.0		3,000,000.0
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				3,000,000.0		$ 3,000,000.0
California [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Surety bonds and standby letters of credit				$ 22,300,000
2022-2023 Policy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	$ 22,500,000
Maximum additional premium charged amount for twelve month policy period, if claims develop adversely	$ 0
Self Insured Programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of worker's compensation exposure covered				17.00%
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
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
Insured Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of worker's compensation exposure covered				83.00%
Description of renewed agreement				Effective July 1, 2022, the Company renewed the arrangement for its insured program, which now continues through June 30, 2023 (the “2022-2023 Policy”). Under the renewed arrangement, the Company can participate in savings up to $22.5 million for the twelve-month policy period. For the 2022-2023 Policy, no additional premium may be charged if claims develop adversely. The 2022-2023 Policy includes a renewal commitment through June 30, 2024.
Worker's compensation risk claim maximum		$ 3,000,000.0
Worker's compensation risk claim maximum			$ 5,000,000.0
Workers compensation liability				$ 53,100,000