The percentage decrease in the cost of the rental rates under the terms of the lease

No definition available.

Name:	nbix_BaseRentalReductionPercentage
Namespace Prefix:	nbix_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense (reversal of expense) in connection with exit or disposal activity (including executory costs such as maintenance charges) net of estimated income from potential subleasing.

+ References

No definition available.

+ Details

Name:	nbix_CeaseUseExpenseReversalOfExpense
Namespace Prefix:	nbix_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Commitment And Contingencies [Line Items]

+ References

No definition available.

+ Details

Name:	nbix_CommitmentAndContingenciesLineItems
Namespace Prefix:	nbix_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease cancellation notice period.

+ References

No definition available.

+ Details

Name:	nbix_LeaseCancellationNoticePeriod
Namespace Prefix:	nbix_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The date of expiration of the sublease agreement between the entity and a third party, in CCYY-MM format.

+ References

No definition available.

+ Details

Name:	nbix_LeaseExpirationMonthAndYear
Namespace Prefix:	nbix_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

The year of expiration of the initial lease term.

+ References

No definition available.

+ Details

Name:	nbix_LeaseExpirationYear
Namespace Prefix:	nbix_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease extension period.

+ References

No definition available.

+ Details

Name:	nbix_LeaseExtensionPeriod
Namespace Prefix:	nbix_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Letter of credit issued by the bank in lieu of a cash security deposit under the terms of a lease, secured by a deposit of equal amount with that bank.

+ References

No definition available.

+ Details

Name:	nbix_LettersOfCreditCollateral
Namespace Prefix:	nbix_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of buildings leased.

+ References

No definition available.

+ Details

Name:	nbix_NumberOfBuildingsLeased
Namespace Prefix:	nbix_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of sublease agreements related to real estate properties.

+ References

No definition available.

+ Details

Name:	nbix_NumberOfLeaseAgreements
Namespace Prefix:	nbix_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of renewal options under the terms of the lease.

+ References

No definition available.

+ Details

Name:	nbix_NumberOfRenewalOptions
Namespace Prefix:	nbix_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Operating lease expiration year.

+ References

No definition available.

+ Details

Name:	nbix_OperatingLeaseExpirationYear
Namespace Prefix:	nbix_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of potential milestone payments to be paid under a license agreement.

+ References

No definition available.

+ Details

Name:	nbix_PotentialMilestonePayments
Namespace Prefix:	nbix_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Royalty rate percentage.

+ References

No definition available.

+ Details

Name:	nbix_RoyaltyRatePercentage
Namespace Prefix:	nbix_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The term whereby the Company leased back the property in a sale leaseback transaction involving the sale of the property to another party and the lease of the property back to the Company, in PnY format.

+ References

No definition available.

+ Details

Name:	nbix_SaleLeasebackTransactionLeasePeriod
Namespace Prefix:	nbix_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total area (square footage) of the subleased property.

+ References

No definition available.

+ Details

Name:	nbix_SubleasedAgreementArea
Namespace Prefix:	nbix_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseAndRentalExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Date which lease or group of leases is set to expire, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of mortgage loans on real estate that were sold during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.6)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The total amount of sublease rental income recognized during the period that reduces the entity's rent expense incurred under operating leases.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

+ Details

Name:	us-gaap_OperatingLeasesRentExpenseSubleaseRentals1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage charged for managing real estate properties.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyManagementFeePercentFee
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The portion of the deferred gain that was recognized in the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77907795&loc=d3e50609-112754

+ Details

Name:	us-gaap_SaleLeasebackTransactionCurrentPeriodGainRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The portion of the gain that will be recorded as income or a reduction in rent expense in future periods less amounts recognized in the current period.

+ References

+ Details

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

- Definition

Amount of cash inflow before closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in investing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51843-112757

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51831-112757

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51840-112757

+ Details

Name:	us-gaap_SaleLeasebackTransactionGrossProceedsInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash inflow after closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51840-112757

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51831-112757

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51843-112757

+ Details

Name:	us-gaap_SaleLeasebackTransactionNetProceedsFinancingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of an asset, typically cash, provided to a counterparty to provide certain assurance of performance by the entity pursuant to the terms of a written or oral agreement, such as a lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8,17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Carrying amount as of the balance sheet date of improvements having a life longer than one year that were made for the benefit of one or more tenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherCommitmentsAxis=nbix_SubleaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherCommitmentsAxis=nbix_SecondSubleaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseArrangementTypeAxis=nbix_AmendedLeaseTermMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies - Additional Information (Detail) ft² in Thousands, $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2007 USD ($) Building	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft² RenewalOptions Lease_Agreements	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2008 USD ($)
Commitment And Contingencies [Line Items]
Sale of facility and associated real property	$ 109.0
Mortgage debt retired	47.7
Cash received net of transaction costs and debt retirement	$ 61.0
Leaseback transaction lease period	12 years
Number of building leased \| Building	2
Net deferred gain on real estate sale			$ 8.8			$ 39.1
Deferred gain recognized on real estate sale			$ 2.1	$ 3.4	$ 3.3
Lease expiration year			2029
Percentage of management fee included in the base annual rent			3.50%
Letter of credit			$ 3.0
Lease extension period			10 years
Number of times to renew the lease contract \| RenewalOptions			2
Lease security deposit			$ 4.7
Subleased area \| ft²			16
Rent expense			$ 5.9	6.0	$ 6.0
Lease expiration year			2029
Milestone payables			$ 132.0
Minimum
Commitment And Contingencies [Line Items]
Lease cancellation, notice period			0 days
Maximum
Commitment And Contingencies [Line Items]
Lease cancellation, notice period			180 days
Royalty, rate			5.00%
Scenario, Forecast
Commitment And Contingencies [Line Items]
Rental income from sublease agreement		$ 0.1
Sublease
Commitment And Contingencies [Line Items]
Number of sublease agreements \| Lease_Agreements			1
Reversal of cease use expense			$ 0.5	$ 0.8
Second Sublease
Commitment And Contingencies [Line Items]
Lease expiration date			2018-03
Amended Lease Term
Commitment And Contingencies [Line Items]
Lease expiration date			Dec. 31, 2029
Percentage reduction in base rental			8.00%
Tenant improvement allowances			$ 13.1
Lease security deposit			$ 3.0