XML 57 R43.htm IDEA: XBRL DOCUMENT
v3.22.2

Note 8 - Preferred Stock and Common Stock Warrants (Details Textual) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions |  | 1 Months Ended | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | --- | ---
Jul. 15, 2022 | Mar. 31, 2022 | Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2022 | Jun. 30, 2021 | Dec. 31, 2021
Common Stock Warrants [Member] |  |  |  |  |  |  |
Fair Value Adjustment of Warrants |  |  | $ 1.9 | $ (4.8) | $ (4.4) | $ (6.8) |
Series A Convertible Preferred Stock [Member] |  |  |  |  |  |  |
Temporary Equity, Shares Outstanding (in shares) |  |  | 78,181 |  | 78,181 |  | 73,713
Temporary Equity, Par or Stated Value Per Share (in dollars per share) |  |  |  |  |  |  | $ 0.0001
Preferred Stock, Convertible, Conversion Price (in dollars per share) |  |  | $ 6.14 |  | $ 6.14 |  |
Series B Convertible Preferred Stock [Member] |  |  |  |  |  |  |
Temporary Equity, Shares Outstanding (in shares) |  |  | 74,694 |  | 74,694 |  | 70,433
Temporary Equity, Par or Stated Value Per Share (in dollars per share) |  |  |  |  |  |  | $ 0.0001
Preferred Stock, Convertible, Conversion Price (in dollars per share) |  |  | $ 6.19 |  | $ 6.19 |  |
Series C Convertible Preferred Stock [Member] |  |  |  |  |  |  |
Temporary Equity, Shares Outstanding (in shares) |  |  | 55,961 |  | 55,961 |  | 42,490
Temporary Equity, Par or Stated Value Per Share (in dollars per share) |  |  |  |  |  |  | $ 0.0001
Temporary Equity, Stock Issued During Period, Shares, New Issues (in shares) |  | 10,500 |  |  |  |  |
Temporary Equity, Issued Price Per Share (in dollars per share) |  | $ 1,000 |  |  |  |  |
Temporary Equity, Stock Issued During Period, Value, New Issues |  | $ 10.5 |  |  |  |  |
Temporary Equity, Stock Issued During Period, Shares Issued for Services (in shares) |  | 210 |  |  |  |  |
Preferred Stock, Convertible, Conversion Price (in dollars per share) |  |  | $ 3.27 |  | $ 3.27 |  |
Convertible Preferred Stock [Member] |  |  |  |  |  |  |
Temporary Equity, Issued Price Per Share (in dollars per share) |  |  | $ 1,000 |  | $ 1,000 |  |
Temporary Stock, Threshold Trading Days for Conversion (Day) |  |  |  |  | 60 days |  |
Temporary Stock, Threshold Consecutive Trading Days for Conversion (Day) |  |  |  |  | 90 days |  |
Temporary Stock, Conversion Price Minimum Percentage |  |  |  |  | 175.00% |  |
Temporary Stock, Maximum Business Days Following FID Event for Conversion (Day) |  |  |  |  | 10 days |  |
Temporary Equity, Dividend Rate Percentage |  |  |  |  | 12.00% |  |
Dividends, Preferred Stock, Paid-in-kind |  |  |  |  | $ 11.5 | $ 7.7 |
Convertible Preferred Stock [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Dividends, Preferred Stock, Paid-in-kind | $ 6.2 |  |  |  |  |  |

X
- Definition The percentage rate used to calculate dividend payments on temporary equity. + References No definition available. + Details
Name: | next_TemporaryEquityDividendRatePercentage
Namespace Prefix: | next_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Per share or per unit amount of Convertible preferred stock securities issued. + References No definition available. + Details
Name: | next_TemporaryEquityIssuedPricePerShare
Namespace Prefix: | next_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Shares issued in lieu of cash for services contributed to the entity. Shares of the stock issued includes, but is not limited to, services contributed by vendors and founders. + References No definition available. + Details
Name: | next_TemporaryEquityStockIssuedDuringPeriodSharesIssuedForServices
Namespace Prefix: | next_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of new stock classified as temporary equity issued during the period. + References No definition available. + Details
Name: | next_TemporaryEquityStockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | next_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The threshold percentage of the conversion price, for conversion of preferred stock. + References No definition available. + Details
Name: | next_TemporaryStockConversionPriceMinimumPercentage
Namespace Prefix: | next_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum business days of conversion price following an FID event of common stock under preferred stock conversion , in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | next_TemporaryStockMaximumBusinessDaysFollowingFidEventForConversion
Namespace Prefix: | next_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Threshold number of consecutive trading days that the Company's weighted average trading price of shares must exceed than threshold percentage of the conversion price for specified number of trading days to trigger force exercise feature. + References No definition available. + Details
Name: | next_TemporaryStockThresholdConsecutiveTradingDaysForConversion
Namespace Prefix: | next_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Threshold number of specified trading days that the Company's weighted average trading price of shares is equal or greater than the conversion price. + References No definition available. + Details
Name: | next_TemporaryStockThresholdTradingDaysForConversion
Namespace Prefix: | next_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of paid and unpaid preferred stock dividends declared with the form of settlement in payment-in-kind (PIK). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 405 -Section 45 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817 + Details
Name: | us-gaap_DividendsPreferredStockPaidinkind
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense (income) related to adjustment to fair value of warrant liability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 480 -SubTopic 10 -Section 25 -Paragraph 13 -URI https://asc.fasb.org/extlink&oid=109262497&loc=d3e20148-110875 + Details
Name: | us-gaap_FairValueAdjustmentOfWarrants
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Per share conversion price of preferred stock. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 13 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644 + Details
Name: | us-gaap_PreferredStockConvertibleConversionPrice
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 480 -SubTopic 10 -Section S99 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=122040564&loc=d3e177068-122764 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (27) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_TemporaryEquityParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(27)(b)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_TemporaryEquitySharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Value of new stock classified as temporary equity issued during the period. + References No definition available. + Details
Name: | us-gaap_TemporaryEquityStockIssuedDuringPeriodValueNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_ClassOfWarrantOrRightAxis=next_CommonStockWarrantsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=next_SeriesAConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=next_SeriesBConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=next_SeriesCConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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