Derivatives (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Sales
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on commodity derivatives included in sales and merchandising revenues	$ 44,290	$ 86,558	$ 105,651	$ 106,389