XML 51 R37.htm IDEA: XBRL DOCUMENT
v3.19.1

Accrued Liabilities and Other Current Liabilities (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Accrued Liabilities and Other Current Liabilities |  |
Employee compensation expense | $ 2,252 | $ 3,130
Project asset costs | 1,091 | 2,014
Valve installation incentive |  | 2,000
Accrued legal services | 306 | 313
Other accrued liabilities | 538 | 896
Total accrued liabilities and other current liabilities | $ 4,187 | $ 8,353

X
- Definition Amount of obligations incurred and payable, pertaining to costs that are statutory in nature, incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include, but not limited to, taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References No definition available. + Details
Name: | next_AccruedLiabilitiesAndOtherLiabilitiesCurrent
Namespace Prefix: | next_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value as of the balance sheet date of obligations incurred through that date and payable for valve installation incentive. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References No definition available. + Details
Name: | next_AccruedValveInstallationIncentiveCurrent
Namespace Prefix: | next_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value as of the balance sheet date of obligations incurred through that date and payable for project asset costs. + References No definition available. + Details
Name: | next_ProjectAssetCostsCurrent
Namespace Prefix: | next_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying value as of the balance sheet date of obligations incurred through that date and payable for professional fees, such as for legal and accounting services received. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6911-107765 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6935-107765 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AccruedProfessionalFeesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_EmployeeRelatedLiabilitiesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e7018-107765 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6911-107765 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6935-107765 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_OtherAccruedLiabilitiesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant