Changes to Accrued Cease-Use Liability (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Beginning balance	$ 62	$ 853
Change in estimate	0	0
Payments	(62)	(66)
Ending balance	$ 0	$ 787

Amount of liability recorded for the net present value estimated difference between 1) the income to be generated under the Sublease and future subleases, and 2) the Lease obligation over the remaining term of the Lease for the space that is occupied by the subtenant.

No definition available.

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