Derivatives - Effect on Income (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Gain (loss) on derivative
Gains or (losses) that were excluded from the assessment of the effectiveness of fair value hedges	$ 0	$ 0	$ 0	$ 0
Commodity contracts
Derivative, credit-risk related contingent features
Net Liability Position Subject to Collateral Requirements	14,000,000		14,000,000		$ 63,200,000
Collateral Posted	(2,200,000)		(2,200,000)		(28,100,000)
Contingent Additional Collateral	11,800,000		11,800,000		$ 35,100,000
Derivatives designated as hedging instruments | Fair value hedges | Cost of revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Derivative Instruments	11,300,000	52,800,000	(19,500,000)	36,700,000
Realized and Unrealized Gain (Loss) on Hedged Items	(900,000)	(48,500,000)	9,800,000	(29,200,000)
Derivatives designated as hedging instruments | Fair value hedges | Commodity contracts for firm commitment hedging | Cost of revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Derivative Instruments	700,000	0	700,000	0
Realized and Unrealized Gain (Loss) on Hedged Items	(800,000)	0	(800,000)	0
Derivatives designated as hedging instruments | Fair value hedges | Commodity contracts for inventory hedging | Cost of revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Derivative Instruments	10,600,000	52,800,000	(20,200,000)	36,700,000
Realized and Unrealized Gain (Loss) on Hedged Items	(100,000)	(48,500,000)	10,600,000	(29,200,000)
Derivatives designated as hedging instruments | Cash flow hedges
Gain (loss) on derivative
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Effective Portion)	28,700,000	(1,100,000)	25,100,000	(1,100,000)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Effective Portion)	(36,400,000)	0	(27,900,000)	0
Amount of Gain (Loss) Recognized in Income (Ineffective Portion)	(700,000)	(300,000)	(3,000,000)	(300,000)
Derivatives designated as hedging instruments | Cash flow hedges | Commodity contracts | Revenue
Gain (loss) on derivative
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Effective Portion)	11,200,000	300,000	(105,300,000)	300,000
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Effective Portion)	16,600,000	0	(30,700,000)	0
Amount of Gain (Loss) Recognized in Income (Ineffective Portion)	2,900,000	(1,200,000)	(12,200,000)	(1,200,000)
Derivatives designated as hedging instruments | Cash flow hedges | Commodity contracts | Cost of revenue
Gain (loss) on derivative
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Effective Portion)	17,400,000	(1,400,000)	130,400,000	(1,400,000)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Effective Portion)	(53,000,000)	0	2,900,000	0
Amount of Gain (Loss) Recognized in Income (Ineffective Portion)	(3,600,000)	900,000	9,200,000	900,000
Derivatives not designated as hedging instruments
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	4,500,000	8,600,000	0	30,200,000
Derivatives not designated as hedging instruments | Commodity contracts | Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	18,300,000	43,200,000	51,700,000	89,200,000
Derivatives not designated as hedging instruments | Commodity contracts | Cost of revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	(14,600,000)	(39,900,000)	(53,300,000)	(68,000,000)
Derivatives not designated as hedging instruments | Foreign currency contracts | Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	1,300,000	3,400,000	7,700,000	2,100,000
Derivatives not designated as hedging instruments | Foreign currency contracts | Other (expense) income, net
Gain (loss) on derivative
Realized and Unrealized Gain (Loss)	$ (500,000)	$ 1,900,000	$ (6,100,000)	$ 6,900,000