Fair Value Measurements (Narrative) (Details) (Significant Unobservable Inputs (Level 3) [Member], USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended	6 Months Ended			12 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member]	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Assets [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Liabilities [Member]	Dec. 31, 2012 Weighted Average [Member] Fair Value, Measurements, Recurring [Member] Inventories Component [Member] Assets [Member]	Jun. 30, 2012 Weighted Average [Member] Fair Value, Measurements, Recurring [Member] Inventories Component [Member] Assets [Member]	Dec. 31, 2012 Weighted Average [Member] Fair Value, Measurements, Recurring [Member] Inventories Component [Member] Liabilities [Member]	Jun. 30, 2012 Weighted Average [Member] Fair Value, Measurements, Recurring [Member] Inventories Component [Member] Liabilities [Member]
Fair Value Measurements [Line Items]
Unrealized gains (losses) on derivative assets and liabilities			$ 109	$ 130	$ (165)
Threshold of relative value of unobservable inputs to the total fair value for Level 3		10.00%
Unobservable Price Component, as a percent	100.00%
Basis						13.50%	8.80%	26.20%	2.30%