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Basis of Presentation - Summary of Unrecognized Compensation Cost Related to Non-vested Awards Granted (Detail) (USD $)
In Thousands, unless otherwise specified
May 02, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unrecognized compensation cost $ 2,100us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
2016  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unrecognized compensation cost 995us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardDateAxis
= bamm_YearOneMember
2017  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unrecognized compensation cost 866us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardDateAxis
= bamm_YearTwoMember
2018  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unrecognized compensation cost 283us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardDateAxis
= bamm_YearThreeMember
2019  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unrecognized compensation cost $ 4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardDateAxis
= bamm_YearFourMember