Financial Instruments and Off-Balance Sheet Risk - Summary of Financial Assets and Financial Liabilities of Partnership Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Financial assets:    
Financial assets $ 157,714 $ 229,890
Financial liabilities:    
Financial liabilities 37,178 89,176
Commodity Fixed Forwards [Member]    
Financial assets:    
Financial assets 157,389 229,679
Financial liabilities:    
Financial liabilities 31,801 80,080
Commodity Swaps and Options [Member]    
Financial assets:    
Financial assets 51 74
Financial liabilities:    
Financial liabilities 4,250 8,424
Commodity Derivatives [Member]    
Financial assets:    
Financial assets 157,440 229,753
Financial liabilities:    
Financial liabilities 36,051 88,601
Interest Rate Swaps    
Financial assets:    
Financial assets 274 137
Financial liabilities:    
Financial liabilities 1,115 553
Commodity Exchange Contracts [Member]    
Financial liabilities:    
Financial liabilities   97
Other Contracts [Member]    
Financial liabilities:    
Financial liabilities 12 22
Quoted Prices in Active Markets Level 1 [Member]    
Financial assets:    
Financial assets 0 0
Financial liabilities:    
Financial liabilities 0 97
Quoted Prices in Active Markets Level 1 [Member] | Commodity Fixed Forwards [Member]    
Financial assets:    
Financial assets 0 0
Financial liabilities:    
Financial liabilities 0 0
Quoted Prices in Active Markets Level 1 [Member] | Commodity Swaps and Options [Member]    
Financial assets:    
Financial assets 0 0
Financial liabilities:    
Financial liabilities 0 0
Quoted Prices in Active Markets Level 1 [Member] | Commodity Derivatives [Member]    
Financial assets:    
Financial assets 0 0
Financial liabilities:    
Financial liabilities 0 97
Quoted Prices in Active Markets Level 1 [Member] | Interest Rate Swaps    
Financial assets:    
Financial assets 0 0
Financial liabilities:    
Financial liabilities 0 0
Quoted Prices in Active Markets Level 1 [Member] | Commodity Exchange Contracts [Member]    
Financial liabilities:    
Financial liabilities   97
Quoted Prices in Active Markets Level 1 [Member] | Other Contracts [Member]    
Financial liabilities:    
Financial liabilities 0 0
Significant Other Observable Inputs Level 2 [Member]    
Financial assets:    
Financial assets 157,714 229,890
Financial liabilities:    
Financial liabilities 37,178 89,079
Significant Other Observable Inputs Level 2 [Member] | Commodity Fixed Forwards [Member]    
Financial assets:    
Financial assets 157,389 229,679
Financial liabilities:    
Financial liabilities 31,801 80,080
Significant Other Observable Inputs Level 2 [Member] | Commodity Swaps and Options [Member]    
Financial assets:    
Financial assets 51 74
Financial liabilities:    
Financial liabilities 4,250 8,424
Significant Other Observable Inputs Level 2 [Member] | Commodity Derivatives [Member]    
Financial assets:    
Financial assets 157,440 229,753
Financial liabilities:    
Financial liabilities 36,051 88,504
Significant Other Observable Inputs Level 2 [Member] | Interest Rate Swaps    
Financial assets:    
Financial assets 274 137
Financial liabilities:    
Financial liabilities 1,115 553
Significant Other Observable Inputs Level 2 [Member] | Commodity Exchange Contracts [Member]    
Financial liabilities:    
Financial liabilities   0
Significant Other Observable Inputs Level 2 [Member] | Other Contracts [Member]    
Financial liabilities:    
Financial liabilities 12 $ 22
Significant Unobservable Inputs Level 3 [Member]    
Financial assets:    
Financial assets $ 0