XML 55 R43.htm IDEA: XBRL DOCUMENT
v3.21.2

Summary of significant accounting policies - Risk of Concentrations of Credit, Significant Customers and Significant Suppliers (Details) - Customers | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Total revenue | Major Customers |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage | 43.50% | 59.60% | 16.40% | 48.40% |
Total revenue | Customer A |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage | 32.10% | 40.80% | 16.40% | 21.20% |
Total revenue | Customer B |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  |  | 17.10% |
Total revenue | Customer C |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  |  | 10.10% |
Total revenue | Customer D |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage | 11.40% |  |  |  |
Total revenue | Customer E |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  | 18.80% |  |  |
Accounts receivable | Major Customers |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  | 53.00% |  | 84.10%
Accounts receivable | Customer A |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  | 21.70% |  | 41.90%
Accounts receivable | Customer D |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  | 20.20% |  |
Accounts receivable | Customer E |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  | 11.10% |  |
Accounts receivable | Customer F |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  |  |  | 10.10%
Accounts receivable | Customer G |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  |  |  | 13.40%
Accounts receivable | Customer H |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Customer concentration risk percentage |  |  |  |  | 18.70%

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ConcentrationRiskLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13531-108611 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13537-108611 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_SignificantOrMajorCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerDMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerEMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_AccountsReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerFMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerGMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=rmb_CustomerHMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |