Derivatives (Details 2) (Sales, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Sales
Derivative Instruments, Gain (Loss) [Line Items]
Gains on commodity derivatives included in sales and merchandising revenues	$ 86,558	$ 30,894	$ 106,389	$ 99,896