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Marketable Securities and Long-Term Investments - Additional Information (Details) - USD ($) | 6 Months Ended
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Jun. 30, 2021 | Jun. 30, 2020
Investments Debt And Equity Securities [Abstract] |  |
Realized gains or losses recognized on sale or maturity of marketable securities | $ 0 | $ 0
Contractual maturity dates of investments | less than one year |

X
- Definition Describes the period of time in which investments will reach maturity. + References No definition available. + Details
Name: | beam_DebtSecuritiesAvailableForSaleMaturityPeriod
Namespace Prefix: | beam_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), excluding other-than-temporary impairment (OTTI). + References No definition available. + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLossExcludingOtherThanTemporaryImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration