| Equity Method Investments and Joint Ventures Disclosure [Text Block] |
6. Equity Investment
The Partnership accounts for its 49% investment in Sisecam Wyoming using the equity method of accounting. Activity related to this investment is as follows:
| | | For the Three Months Ended September 30, | | | For the Nine Months Ended September 30, | |
| (In thousands) | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| Balance at beginning of period | | $ | 277,475 | | | $ | 258,498 | | | $ | 250,244 | | | $ | 257,355 | |
| Income (loss) allocation to NRP’s equity interests (1) | | | (3,013 | ) | | | (1,342 | ) | | | (13,531 | ) | | | 8,074 | |
| Amortization of basis difference | | | (1,112 | ) | | | (1,048 | ) | | | (3,327 | ) | | | (3,327 | ) |
| Capital investment | | | — | | | | — | | | | 39,200 | | | | — | |
| Other comprehensive income (loss) | | | 847 | | | | (2,391 | ) | | | 1,611 | | | | (545 | ) |
| Distributions | | | — | | | | — | | | | — | | | | (7,840 | ) |
| Balance at end of period | | $ | 274,197 | | | $ | 253,717 | | | $ | 274,197 | | | $ | 253,717 | |
| (1) | Amounts reclassified into income (loss) out of accumulated other comprehensive loss were $0.7 million and $1.0 million for the three months ended September 30, 2026 and 2025, respectively, and $3.8 million and $2.3 million for the nine months ended September 30, 2026 and 2025, respectively. |
During the nine months ended September 30, 2026, NRP and Sisecam Wyoming's managing partner made a capital investment into Sisecam Wyoming ($39.2 million for NRP's 49%) to reduce outstanding amounts under Sisecam Wyoming's bank credit facility.
The following table represents summarized financial information for Sisecam Wyoming as derived from their respective unaudited financial statements for the three and nine months ended September 30, 2026 and 2025:
| | | For the Three Months Ended September 30, | | | For the Nine Months Ended September 30, | |
| (In thousands) | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| Net sales | | $ | 113,155 | | | $ | 123,847 | | | $ | 373,288 | | | $ | 413,754 | |
| Gross profit (loss) | | | 1,458 | | | | 4,264 | | | | (2,491 | ) | | | 38,467 | |
| Net income (loss) | | | (6,149 | ) | | | (2,739 | ) | | | (27,614 | ) | | | 16,477 | |
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