Changes to Accrued Cease-Use Liability (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Commitments And Contingencies Disclosure [Abstract]
Beginning balance	$ 2,994	$ 3,492	$ 3,096	$ 3,686
Payments	(102)	(197)	(204)	(391)
Ending balance	$ 2,892	$ 3,295	$ 2,892	$ 3,295

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