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Fair Value (Details) - Schedule of beginning and ending balances for the liabilities measured at fair value $ in Thousands | 12 Months Ended
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Dec. 31, 2020 USD ($)
Warrants: |
Balance | $ 3,531
Issuance of warrants in connection with Fortress Financing Agreement | 190
Fair value adjustment of outstanding warrants | 97,604
Balance | $ 101,325

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- Definition Amount of fair value issuance of warrants in connection with Fortress Financing Agreement. + References No definition available. + Details
Name: | nn_FairValueIssuanceOfWarrantInConnectionWithFortressFinancingAgreement
Namespace Prefix: | nn_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | nn_WarrantsAbstract
Namespace Prefix: | nn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of addition (reduction) to the amount at which a liability could be incurred (settled) in a current transaction between willing parties. + References No definition available. + Details
Name: | us-gaap_LiabilitiesFairValueAdjustment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration