Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2014
Inventories
Crude oil	156,473us-gaap_EnergyRelatedInventoryPetroleum	46,156us-gaap_EnergyRelatedInventoryPetroleum	$ 136,722us-gaap_EnergyRelatedInventoryPetroleum
Natural gas liquids:
Propane	85,159	45,428	207,694
Butane and other	19,051	24,090
Refined products	23,209
Renewables	11,778ngl_EnergyRelatedInventoryRenewables		36,517ngl_EnergyRelatedInventoryRenewables
Other	14,490us-gaap_OtherInventoryNetOfReserves	11,221us-gaap_OtherInventoryNetOfReserves
Inventories	310,160us-gaap_InventoryNet	126,895us-gaap_InventoryNet	$ 941,589us-gaap_InventoryNet
Consolidated total revenues \| Customer concentration risk \| Crude oil and natural gas liquids \| Largest customer
Concentration of Credit Risk
Percentage of concentration risk	10.00%	10.00%
Consolidated accounts receivable \| Customer concentration risk \| Crude oil logistics
Concentration of Credit Risk
Number of customers or suppliers		1
Percentage of concentration risk		10.00%

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

No definition available.

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- Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Represents the number of accounts included in a review of concentration risk. May include, but is not limited to, number of customers, number of suppliers, or number of contracts.

+ References

No definition available.

+ Details

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- Details

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

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+ Details

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Period Type:	duration

- Definition

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

+ References

+ Details

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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

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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

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-Subparagraph (SX 210.5-02.6(a))

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-Paragraph 1

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- Details

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- Definition

Carrying amount, net of valuation reserves and allowances, as of the balance sheet date of inventories not otherwise specified in the taxonomy.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.BB)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6)

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

+ Details

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- Details

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