Significant Accounting Policies (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014	Mar. 31, 2013
Inventories
Crude oil	$ 136,722us-gaap_EnergyRelatedInventoryPetroleum	$ 156,473us-gaap_EnergyRelatedInventoryPetroleum	$ 46,156us-gaap_EnergyRelatedInventoryPetroleum
Natural gas liquids:
Propane	207,694	85,159	45,428
Butane	84,822ngl_EnergyRelatedInventoryButane	15,106ngl_EnergyRelatedInventoryButane
Other	11,390	14,490
Butane	27,091	3,945
Refined products:
Gasoline	219,111ngl_EnergyRelatedInventoryGasoline	15,597ngl_EnergyRelatedInventoryGasoline
Diesel	214,567ngl_EnergyRelatedInventoryDiesel	7,298ngl_EnergyRelatedInventoryDiesel
Other	11,390	14,490
Other	3,675ngl_EnergyRelatedInventoryOther	314ngl_EnergyRelatedInventoryOther
Renewables	36,517ngl_EnergyRelatedInventoryRenewables	11,778ngl_EnergyRelatedInventoryRenewables
Inventories	$ 941,589us-gaap_InventoryNet	$ 310,160us-gaap_InventoryNet	$ 126,895us-gaap_InventoryNet

Represents the carrying amount as of the balance sheet date of butane.

No definition available.

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Namespace Prefix:	ngl_
Data Type:	xbrli:monetaryItemType
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- Definition

Represents the carrying amount as of the balance sheet date of Diesel.

+ References

No definition available.

+ Details

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Namespace Prefix:	ngl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the carrying amount as of the balance sheet date of Gasoline.

+ References

No definition available.

+ Details

Name:	ngl_EnergyRelatedInventoryGasoline
Namespace Prefix:	ngl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ngl_EnergyRelatedInventoryNaturalGasLiquidsAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the carrying amount as of the balance sheet date of energy related inventories not seperately disclosed.

+ References

No definition available.

+ Details

Name:	ngl_EnergyRelatedInventoryOther
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Energy Related Inventory Other Natural Gas Liquids

+ References

No definition available.

+ Details

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Namespace Prefix:	ngl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the carrying amount as of the balance sheet date of other refined products.

+ References

No definition available.

+ Details

Name:	ngl_EnergyRelatedInventoryOtherRefinedProducts
Namespace Prefix:	ngl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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- Definition

Represents the carrying amount as of the balance sheet date of renewables.

+ References

No definition available.

+ Details

Name:	ngl_EnergyRelatedInventoryRenewables
Namespace Prefix:	ngl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of petroleum or crude oil.

+ References

+ Details

Name:	us-gaap_EnergyRelatedInventoryPetroleum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of product derived from petroleum during the processing of oil or natural gas which is then used as a heat source or fuel.

+ References

+ Details

Name:	us-gaap_EnergyRelatedInventoryPropaneGas
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or 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 210.5-02.6(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 330

-SubTopic 10

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6386567&loc=d3e3927-108312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

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