XML 50 R33.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Summary of Investments Classified as Available-For-Sale Securities (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items] |  |
Aggregate Estimated Fair Value | $ 725,227 | $ 508,578
Commercial paper |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Aggregate Estimated Fair Value | 94,572 | 75,362
Corporate debt securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Aggregate Estimated Fair Value | 544,978 | 414,815
Securities of government-sponsored entities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Aggregate Estimated Fair Value | 85,677 | 18,401
Short-term investments |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 510,889 | 261,675
Gross Unrealized Gains | 8 | 1
Gross Unrealized Losses | (1,698) | (459)
Aggregate Estimated Fair Value | 509,199 | 261,217
Short-term investments | Commercial paper |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 94,617 | 75,396
Gross Unrealized Gains | 0 | 1
Gross Unrealized Losses | (45) | (35)
Aggregate Estimated Fair Value | $ 94,572 | $ 75,362
Short-term investments | Commercial paper | Maximum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 1 year | 1 year
Short-term investments | Corporate debt securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 395,385 | $ 178,776
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (1,598) | (400)
Aggregate Estimated Fair Value | $ 393,787 | $ 178,376
Short-term investments | Corporate debt securities | Maximum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 1 year | 1 year
Short-term investments | Securities of government-sponsored entities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 20,887 | $ 7,503
Gross Unrealized Gains | 8 | 0
Gross Unrealized Losses | (55) | (24)
Aggregate Estimated Fair Value | $ 20,840 | $ 7,479
Short-term investments | Securities of government-sponsored entities | Maximum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 1 year | 1 year
Long-term investments |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 216,270 | $ 248,753
Gross Unrealized Gains | 228 | 0
Gross Unrealized Losses | (470) | (1,392)
Aggregate Estimated Fair Value | 216,028 | 247,361
Long-term investments | Corporate debt securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 151,594 | 237,749
Gross Unrealized Gains | 66 | 0
Gross Unrealized Losses | (469) | (1,310)
Aggregate Estimated Fair Value | $ 151,191 | $ 236,439
Long-term investments | Corporate debt securities | Minimum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 1 year | 1 year
Long-term investments | Corporate debt securities | Maximum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 2 years | 2 years
Long-term investments | Securities of government-sponsored entities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 64,676 | $ 11,004
Gross Unrealized Gains | 162 | 0
Gross Unrealized Losses | (1) | (82)
Aggregate Estimated Fair Value | $ 64,837 | $ 10,922
Long-term investments | Securities of government-sponsored entities | Minimum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 1 year | 1 year
Long-term investments | Securities of government-sponsored entities | Maximum |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available for sale securities contractual maturity | 2 years | 2 years

X
- Definition The term of contractual maturity for available for sale debt securities, in PnY format. + References No definition available. + Details
Name: | nbix_AvailableForSaleDebtSecuritiesContractualMaturity
Namespace Prefix: | nbix_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=us-gaap_CommercialPaperMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=nbix_SecuritiesOfGovernmentSponsoredEntitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=nbix_LongTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |