Mineral Rights - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Extractive Industries [Abstract]
Total depletion and amortization expense on mineral rights	$ 19.9	$ 12.5

Depletion and amortization expense on coal and other mineral rights.

No definition available.

Name:	nrp_DepletionAndAmortizationExpenseOnCoalAndOtherMineralRights
Namespace Prefix:	nrp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration