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Inventory - Schedule of Inventory Allowance (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Inventory Valuation Reserves [Roll Forward]
Beginning balance	$ 5,867	$ 4,004
Allowance for obsolescence	61	1,863
Write-offs	(3,409)	0
Ending balance	$ 2,519	$ 5,867

X

- Definition

Inventory Allowance, Allowance For Obsolescence

+ References

No definition available.

+ Details

Name:	ngs_InventoryAllowanceAllowanceForObsolescence
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Inventory Valuation Reserves

+ References

No definition available.

+ Details

Name:	ngs_InventoryValuationReservesRollForward
Namespace Prefix:	ngs_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Inventory Write-Offs

+ References

No definition available.

+ Details

Name:	ngs_InventoryWriteOffs
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of valuation reserve for inventory.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 330
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.BB)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480581/330-10-S99-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant