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Fair Value Measurements - Contractual Override, Note Receivable and Long-Term Debt (Detail) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Contracts receivable—affiliate, current and long-term $ 4,891 $ 4,870
Fair Value, Inputs, Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Contracts receivable—affiliate, current and long-term 4,158 5,162
Nrp Lp Senior Notes [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount 422,923 422,167
Estimated Fair Value 277,313 423,780
Opco Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount 587,073 668,056
Estimated Fair Value 383,065 672,740
Opco Revolving Credit Facility And Term Loan Facility    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount 290,000 275,000
Estimated Fair Value 290,000 275,000
Nrp Oil And Gas Revolving Credit Facility    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount 85,000 110,000
Estimated Fair Value $ 85,000 $ 110,000