Represents the accrued amount of milestone payments payable by an entity.

No definition available.

Name:	nvax_AccruedMilestonePayment
Namespace Prefix:	nvax_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the aggregate amount of payments made under the license agreement as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	nvax_AggregatePaymentsMadePerLicenseAgreement
Namespace Prefix:	nvax_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of increase in license maintenance fees.

+ References

No definition available.

+ Details

Name:	nvax_IncreaseInLicenseMaintenanceFees
Namespace Prefix:	nvax_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of increase in milestone payment.

+ References

No definition available.

+ Details

Name:	nvax_IncreaseInMilestonePayment
Namespace Prefix:	nvax_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Rental square footage of building.

+ References

No definition available.

+ Details

Name:	nvax_RentalSquareFootageOfBuilding
Namespace Prefix:	nvax_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseAndRentalExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918643-209977

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

+ Details

Name:	us-gaap_OperatingLeasePayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

+ Details

Name:	us-gaap_OperatingLeasesRentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=nvax_GaithersburgMarylandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) a	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)
Rent expense			$ 8.4	$ 7.0	$ 4.2
Accrued milestone payment associated with the first Phase 3 clinical trial						$ 3.0
Aggregate amount of payments made under license agreement			$ 7.6
Gaithersburg, Maryland [Member]
Rental Square Footage of Building \| a			147,000
Gaithersburg, Maryland [Member] \| Subsequent Event [Member]
Termination Fee	$ 5.3
Gaithersburg, Maryland [Member] \| Scenario, Forecast [Member]
Total Termination Expenses		$ 1.0
Maximum [Member]
Increase In License Maintenance Fees			$ 0.3
Increase In Milestone Payment			15.0
Minimum [Member]
Increase In License Maintenance Fees			0.2
Increase In Milestone Payment			$ 14.0