Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014 Commodity futures contracts Cash Flow Hedges MMBTU	Sep. 30, 2014 Commodity futures contracts Cash Flow Hedges MMBTU	Sep. 30, 2013 Commodity futures contracts Cash Flow Hedges MMBTU	Sep. 30, 2014 Forward exchange contracts Derivatives not designated as hedging instruments	Sep. 30, 2013 Forward exchange contracts Derivatives not designated as hedging instruments	Sep. 30, 2013 Forward exchange contracts Derivatives not designated as hedging instruments
Derivatives and Hedges
Coverage of commodity futures contracts (in MM BTUs)	1,800,000	1,800,000	6,600,000
Immaterial unrecognized loss included in Accumulated OCI	$ 1	$ 1	$ 1
Period during which unrecognized gain included in Accumulated OCI will be reclassified into earnings		15 months
Commodity futures contracts gain (loss) recognized in OCI	1	3
Commodity futures contracts Gain (Loss) reclassified from accumulated OCI into income		2
Forward exchange contracts in various currencies				520	740	740
Forward exchange contracts loss recognized in income				$ 1	$ (7)	$ (19)