XML 35 R44.htm IDEA: XBRL DOCUMENT v3.3.0.814
Fair Value Measurements - Summary of Changes of Derivative Commodity Instruments in Fair Value (Details) - Derivative Commodity Instruments - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of period $ (14,063) $ 5,207 $ 24,436 $ 18,289
Realized gains (losses) (2,820) 10,769 10,994 8,581
Unrealized gains (losses) relating to instruments held at the reporting date (3,569) 9,348 (42,068) (3,734)
Settlements during period 2,820 (10,438) (10,994) (8,250)
Balance at end of period (17,632) 14,886 (17,632) 14,886
Mark-to-market loss included in earnings, unrealized $ 5,400 $ 12,200 $ 20,200 $ 9,600