Derivative Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Before-tax effect of derivative instruments not designated as hedging instruments on the consolidated statements of operations
Unrealized loss on commodity contracts	$ (1,575)	[1]	$ (4,673)	[1]
Realized gain (loss) on commodity contracts	(941)	[1]	1,869	[1]
Unrealized gain on interest rate swap	37	[2]	37	[2]
Realized loss on interest rate swap	(67)	[2]	(63)	[2]
Total activity for derivatives not designated as hedging instruments	$ (2,546)		$ (2,830)

[1] Included in price risk management activities on the consolidated statements of operations. Price risk management activities totaled $(2,516) and $(2,804) for the three months ended March 31, 2014 and 2013, respectively.

[2] Included in interest expense, net on the consolidated statements of operations.