BIAL Agreement - Additional Information (Detail) - B I A L $ in Millions	3 Months Ended
Mar. 31, 2017 USD ($)
License Agreement [Line Items]
License agreement date	Feb. 09, 2017
Up-front license fees	$ 30
Milestone payables	$ 115

Collaborative arrangement up-front payment to be paid.

No definition available.

Name:	nbix_CollaborativeArrangementUpfrontPaymentToBePaid
Namespace Prefix:	nbix_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration