XML 74 R59.htm IDEA: XBRL DOCUMENT
v3.21.1

Deferred Compensation Plans (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Compensation Related Costs [Abstract] |  |
Participant's maximum compensation deferral percentage | 90.00% |
Company owned life insurance | $ 2,000,000.0 | $ 1,500,000
Gain (loss) on company owned life insurance | 168,000 | 218,800
Deferred compensation obligation | $ 2,200,000 | $ 1,700,000
Deferred restricted stock shares (in shares) | 45,998 | 85,565
Deferred compensation arrangement with individual, shares issued (in shares) | 145,702 | 89,187
Deferred compensation arrangement, fair value of shares issued | $ 2,200,000 | $ 1,700,000

X
- Definition Deferred Compensation Arrangement With Individual Deferred Restricted Stock + References No definition available. + Details
Name: | ngs_DeferredCompensationArrangementWithIndividualDeferredRestrictedStock
Namespace Prefix: | ngs_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Deferred Compensation Arrangement With Individual Maximum Annual Contributions Per Employee Percent + References No definition available. + Details
Name: | ngs_DeferredCompensationArrangementWithIndividualMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix: | ngs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The total fair value of shares issued during the period under a deferred compensation arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualFairValueOfSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of shares issued pursuant to the terms of a deferred compensation arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition This item represents the amount that could be realized under a life insurance contract or contracts owned by the Entity as of the date of the statement of financial position. Such Entity-owned life insurance policies are commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI). + 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 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 30 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6384206&loc=d3e41899-111602 + Details
Name: | us-gaap_LifeInsuranceCorporateOrBankOwnedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The change in cash surrender or contract value during the period which adjusted the amount of premiums paid in determining the expense or income recognized under the contract for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 30 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6384439&loc=d3e42048-111605 + Details
Name: | us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration