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Workers' Compensation - Summarizes Aggregate Workers' Compensation Reserve Activity (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Workers Compensation Reserve [Abstract]    
Workers' compensation claims liabilities, Beginning balance $ 215,982us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent $ 112,444us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent
Claims expense accrual:    
Current period 26,236bbsi_WorkersCompensationExpenseAccrualClaimsForCurrentPeriod 16,351bbsi_WorkersCompensationExpenseAccrualClaimsForCurrentPeriod
Prior periods (3,186)bbsi_WorkersCompensationExpenseAccrualClaimsForPriorPeriods 3,801bbsi_WorkersCompensationExpenseAccrualClaimsForPriorPeriods
Total expense accrual 23,050bbsi_WorkersCompensationExpenseAccrualClaims 20,152bbsi_WorkersCompensationExpenseAccrualClaims
Claim payments related to:    
Current period 776bbsi_WorkersCompensationClaimPaymentsCurrentPeriod 399bbsi_WorkersCompensationClaimPaymentsCurrentPeriod
Prior periods 15,991bbsi_ClaimPaymentsPriorPeriod 12,062bbsi_ClaimPaymentsPriorPeriod
Total paid 16,767bbsi_WorkersCompensationClaimPayments 12,461bbsi_WorkersCompensationClaimPayments
Workers' compensation claims liabilities, Ending balance 222,265us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent 120,135us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent
Incurred but not reported (IBNR) $ 115,661bbsi_WorkersCompensationIncurredButNotReported $ 69,185bbsi_WorkersCompensationIncurredButNotReported