Derivatives - Effect on Income (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Gain (loss) on derivative
Gains or (losses) recognized in income representing hedge ineffectiveness	$ 1,700,000	$ 700,000
Gains or (losses) that were excluded from the assessment of the effectiveness of fair value hedges	0	0
Potential Collateral Requirements for Derivative Liabilities with Credit-Risk-Contingent Features
Net derivatives liability positions with credit contingent features	5,000,000		$ 15,200,000
Maximum potential collateral requirements	5,000,000		15,200,000
Collateral posted and held by our counterparties	0		$ 0
Derivatives designated as hedging instruments | Fair value hedges
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Derivative Instruments	5,300,000	3,800,000
Realized and Unrealized Gain (Loss) on Hedged Items	(3,600,000)	(3,200,000)
Derivatives designated as hedging instruments | Fair value hedges | Commodity contracts | Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Derivative Instruments	0	86,300,000
Derivatives designated as hedging instruments | Fair value hedges | Commodity contracts | Cost of revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Derivative Instruments	5,300,000	(82,400,000)
Derivatives designated as hedging instruments | Fair value hedges | Commodity contracts for inventory hedging | Revenue
Gain (loss) on derivative
Realized and Unrealized Gain (Loss) on Hedged Items	0	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 Hedged Items	(3,600,000)	(3,200,000)
Derivatives designated as hedging instruments | Cash flow hedges
Gain (loss) on derivative
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Effective Portion)	7,100,000	(2,200,000)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income (Effective Portion)	(3,400,000)	(2,000,000)
Amount of Gain (Loss) Recognized in Income (Ineffective Portion and Amount Excluded from Effectiveness Testing)	(2,000,000)	2,800,000
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)	57,100,000	(46,500,000)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income (Effective Portion)	(10,100,000)	52,700,000
Amount of Gain (Loss) Recognized in Income (Ineffective Portion and Amount Excluded from Effectiveness Testing)	18,200,000	(100,000)
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)	(50,000,000)	44,200,000
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income (Effective Portion)	6,800,000	(54,700,000)
Amount of Gain (Loss) Recognized in Income (Ineffective Portion and Amount Excluded from Effectiveness Testing)	(20,200,000)	2,900,000
Derivatives not designated as hedging instruments
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	8,300,000	(11,900,000)
Derivatives not designated as hedging instruments | Commodity contracts
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	10,400,000	(8,600,000)
Derivatives not designated as hedging instruments | Commodity contracts | Revenue
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	49,200,000	38,900,000
Derivatives not designated as hedging instruments | Commodity contracts | Cost of revenue
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	(38,800,000)	(47,500,000)
Derivatives not designated as hedging instruments | Foreign currency contracts
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	(2,000,000)	(3,300,000)
Derivatives not designated as hedging instruments | Foreign currency contracts | Revenue
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	(500,000)	1,900,000
Derivatives not designated as hedging instruments | Foreign currency contracts | Other (expense) income, net
Gain (loss) on derivative
Amount of Realized and Unrealized Gain (Loss)	$ (1,600,000)	$ (5,200,000)