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Fair Value (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Contractual over ride and long-term debt
Fair value as of contractual overriding agreement, current and long-term	$ 10,291.0
Carrying value as of contractual overriding agreement	8,998.0
Fair value as of long-term debt, current and long-term	893,650.0	915,959.0
Carrying value as of fair value as of long-term debt	$ 851,878.0	$ 867,070.0

X

- Definition

Contractual override affiliates.

+ References

No definition available.

+ Details

Name:	nrp_ContractualOverrideAffiliates
Namespace Prefix:	nrp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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- Definition

Contractual override affiliates fair value disclosure.

+ References

No definition available.

+ Details

Name:	nrp_ContractualOverrideAffiliatesFairValueDisclosure
Namespace Prefix:	nrp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	nrp_ContractualOverRideAndLongTermDebtAbstract
Namespace Prefix:	nrp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Long term debt excluding credit facility.

+ References

No definition available.

+ Details

Name:	nrp_LongTermDebtExcludingCreditFacility
Namespace Prefix:	nrp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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