Leases - Summary of Minimum Lease Payments for Operating Lease Liabilities (Parenthetical) (Detail) $ in Millions	Mar. 31, 2020 USD ($)
Leases [Abstract]
Non-cancelable future minimum lease payments for operating leases that have not yet commenced	$ 28.3

Non cancelable future minimum lease payments for operating leases not yet commenced.

No definition available.

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