Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Contractual Override, Note Receivable and Long-Term Debt

The following table shows the carrying value and estimated fair value of the Partnership's debt and contract receivable:

		December 31,
		2021				2020
(In thousands)	Fair Value Hierarchy Level	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Debt:
NRP 2025 Senior Notes	1	$	296,236	$	300,000	$	295,160	$	274,500
Opco Senior Notes (1)	3	137,309		138,484		176,339		162,760
Opco Credit Facility	3	—		—		—		—
Assets:
Contract receivable, net (current and long-term) (2)	3	$	33,612	$	26,010	$	35,313	$	27,025