Derivative Instruments and Hedging Activities (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Asset	$ 3,019,000	$ 50,824,000
Fair Value Liability	13,912,000	192,000
Unrealized losses included in accumulated other comprehensive income, pretax	10,900,000	50,600,000
Unrealized gain (loss) included in accumulated other comprehensive income, net of tax	6,600,000	30,700,000
Expected reclassification of income (loss) from commodity hedges over the next 12 months	6,600,000
Derivatives Designated as Hedging Instruments
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Asset	13,792,000	54,424,000
Fair Value Liability	24,685,000	3,822,000
Derivatives Designated as Hedging Instruments | Commodity contracts | Current Assets
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Asset	3,019,000	50,824,000
Derivatives Designated as Hedging Instruments | Commodity contracts | Current liabilities
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Liability	$ 13,912,000	$ 192,000