Description of Plan - Additional Information (Detail) - EBP 007 [Member] - USD ($)	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
EBP, Description of Plan [Line Items]
Employee benefit plan participant contribution year age	50
Participant contribution auto increase minimum percentage	1.00%
Participant contribution auto increase maximum percentage	3.00%
EBP, employer contribution, matching percentage	50.00%
EBP, employer contribution, participant compensation matched, percentage	8.00%
Participant contribution rollover from qualified pension plan	$ 2,837,896
Employee benefit plan, note receivable from participant, account, minimum borrowing, amount	1,000
Employee benefit plan, note receivable from participant, account, maximum borrowing, amount	$ 50,000
Employee benefit plan, note receivable from participant, account, maximum borrowing, to total account, percentage	50.00%
Employee benefit plan note receivable from participant account loan period	15 years
Cumulative deemed distributions	$ 553,900	$ 3,752,882
EBP, forfeited nonvested account	1,407,176	$ 3,486,314
EBP, forfeited nonvested account, decrease from employer contribution	1,966,383
Employee benefit plan distrubution of benefit vesting balance	$ 1,000
Minimum [Member]
EBP, Description of Plan [Line Items]
Employee benefit plan, note receivable from participant, account, maximum borrowing, to total account, percentage	3.25%
Employee benefit plan note receivable from participant account loan period	1 year
Maximum [Member]
EBP, Description of Plan [Line Items]
Employee benefit plan, note receivable from participant, account, maximum borrowing, to total account, percentage	10.50%
Employee benefit plan note receivable from participant account loan period	5 years
Three Years Of Service [Member]
EBP, Description of Plan [Line Items]
Employee benefit plan employer matching and core contributions percentage	100.00%
Non Collectively Bargained Participants [Member]
EBP, Description of Plan [Line Items]
EBP, participant contribution, automatic, deferral rate	8.00%
Collectively Bargained Participants [Member]
EBP, Description of Plan [Line Items]
EBP, participant contribution, automatic, deferral rate	6.00%

Cumulative deemed distributions.

No definition available.

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Period Type:	instant

- Definition

Employee benefit plan distrubution of benefit vesting balance.

+ References

No definition available.

+ Details

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Namespace Prefix:	ngg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Employee benefit plan employer matching and core contributions percentage.

+ References

No definition available.

+ Details

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- Definition

Employee benefit plan note receivable from participant account loan period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
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- Definition

Employee benefit plan participant contribution year age.

+ References

No definition available.

+ Details

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- Definition

Participant contribution auto increase maximum percentage.

+ References

No definition available.

+ Details

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- Definition

Participant contribution auto increase minimum percentage.

+ References

No definition available.

+ Details

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- Definition

Participant contribution rollover from qualified pension plan.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-SubTopic 205
-Topic 962
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

+ Details

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- Definition

Percentage of employer matching contribution on eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Period Type:	duration

- Definition

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of plan asset, in forfeited nonvested account, no longer allocated to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from employer contribution.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(5)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

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- Definition

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

+ References

+ Details

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- Definition

Amount of minimum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Namespace Prefix:	us-gaap-ebp_
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- Details

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- Details

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- Details

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