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Concentration Risk - Additional Information (Detail) - Customer Concentration Risk [Member] | 3 Months Ended
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Jun. 30, 2017 Customer
Sales Revenue, Goods, Net |
Concentration Risk [Line Items] |
Number of customers | 3
Accounts Receivable [Member] |
Concentration Risk [Line Items] |
Number of customers | 3

X
- Definition Represents the number of customers. + References No definition available. + Details
Name: | nbix_NumberOfCustomers
Namespace Prefix: | nbix_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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