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v3.25.2

LONG-TERM INVESTMENT - Change of share of results of associates (Details) - USD ($) | 6 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Sep. 30, 2024
LONG-TERM INVESTMENT |  |
Beginning balance | $ 204,648 |
Addition | 126,333 | $ 204,648
Ending balance | $ 330,981 | $ 204,648

X
- Definition Amount of share of results of associates as part of equity method investment. + References No definition available. + Details
Name: | bgm_EquityMethodInvestmentShareOfResultsOfAssociates
Namespace Prefix: | bgm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of recognized share of results of associates. + References No definition available. + Details
Name: | bgm_EquityMethodInvestmentShareOfResultsOfAssociatesAddition
Namespace Prefix: | bgm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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