XML 31 R37.htm IDEA: XBRL DOCUMENT v2.4.0.6

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2011 Y
Summary of Significant Accounting Policies (Textuals) [Abstract]
Period of assets which are deprecated on a straight line basis over their useful lives, Minimum	3
Period of assets which are deprecated on a straight line basis over their useful lives, Maximum	20
Maturity of cash and cash equivalents	3 months

X

- Definition

Period for recognition of for cash equivalents maximum.

+ References

No definition available.

+ Details

Name:	nrp_PeriodForRecognitionOfForCashEquivalentsMaximum
Namespace Prefix:	nrp_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

X

- Details

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

X

- Definition

The maximum useful life of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLifeMaximum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The minimum useful life of long lived, physical assets used in the normal conduct of business and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLifeMinimum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration