Income Taxes (Details) (USD $)	9 Months Ended
Dec. 31, 2013 item
Income Taxes
Number of taxable corporate subsidiaries in United States	3
Number of taxable corporate subsidiaries in Canada	4
Minimum percentage of qualifying income of non-taxable subsidiaries	90.00%
Uncertain tax positions	$ 0

Represents the minimum percentage of qualifying income of non-taxable subsidiaries for both the calendar years since the entity's initial public offering.

No definition available.

+ Details

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- Definition

Represents the number of Canadian subsidiaries that are subject to income tax in Canada.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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Period Type:	instant

- Definition

Represents the number of domestic corporate subsidiaries that are subject to income tax.

+ References

No definition available.

+ Details

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Namespace Prefix:	ngl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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- Definition

Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15A

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

+ Details

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