Fair Value Measurements - Fair Value of Financial Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets remeasured	$ 0	$ 0
Liabilities remeasured	0	0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	25,356,000	24,449,000
Fair value of financial assets, Total	27,445,000	26,864,000
Fair value of other current liabilities	50,276,000
Fair value of other non-current liabilities	37,725,000	80,092,000
Fair value of financial liabilities, Total	88,001,000	82,507,000
Fair Value, Measurements, Recurring \| NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	2,089,000	2,415,000
Fair value of other non-current liabilities	22,521,000	19,962,000
Fair Value, Measurements, Recurring \| Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	48,187,000
Fair value of other non-current liabilities	15,204,000	60,130,000
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	25,356,000	24,449,000
Fair value of financial assets, Total	27,445,000	26,864,000
Fair value of other current liabilities	2,089,000
Fair value of other non-current liabilities	22,521,000	19,962,000
Fair value of financial liabilities, Total	24,610,000	22,377,000
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	2,089,000	2,415,000
Fair value of other non-current liabilities	22,521,000	19,962,000
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	0
Fair value of other non-current liabilities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	0	0
Fair value of financial assets, Total	0	0
Fair value of other current liabilities	48,187,000
Fair value of other non-current liabilities	15,204,000	60,130,000
Fair value of financial liabilities, Total	63,391,000	60,130,000
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	0	0
Fair value of other non-current liabilities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	48,187,000
Fair value of other non-current liabilities	15,204,000	60,130,000
Fair Value, Measurements, Recurring \| NQDC Plan assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	2,089,000	2,415,000
Fair value of other non-current assets	22,521,000	19,962,000
Fair Value, Measurements, Recurring \| NQDC Plan assets \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	2,089,000	2,415,000
Fair value of other non-current assets	22,521,000	19,962,000
Fair Value, Measurements, Recurring \| NQDC Plan assets \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	0	0
Fair value of other non-current assets	0	0
Fair Value, Measurements, Recurring \| Restricted Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	2,835,000	4,487,000
Fair Value, Measurements, Recurring \| Restricted Investments \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	2,835,000	4,487,000
Fair Value, Measurements, Recurring \| Restricted Investments \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	$ 0	$ 0

Other assets current fair value disclosure.

No definition available.

Name:	bmrn_OtherAssetsCurrentFairValueDisclosure
Namespace Prefix:	bmrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Other assets noncurrent fair value disclosure.

+ References

No definition available.

+ Details

Name:	bmrn_OtherAssetsNoncurrentFairValueDisclosure
Namespace Prefix:	bmrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Other liabilities current fair value disclosure.

+ References

No definition available.

+ Details

Name:	bmrn_OtherLiabilitiesCurrentFairValueDisclosure
Namespace Prefix:	bmrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Other liabilities noncurrent fair value disclosure.

+ References

No definition available.

+ Details

Name:	bmrn_OtherLiabilitiesNoncurrentFairValueDisclosure
Namespace Prefix:	bmrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=bmrn_NonqualifiedDeferredCompensationPlanLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=bmrn_ContingentConsiderationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=bmrn_NonqualifiedDeferredCompensationPlanAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=bmrn_RestrictedInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: