Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 5,300
2012 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	2,276
2013 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	1,221
2014 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	732
2015 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	237
2016 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	109
2017 - 2051 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	740
Total [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 5,315