Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 4,400
2013 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	1,937
2014 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	1,199
2015 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	424
2016 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	147
2017 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	88
2018 - 2052 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	582
Total [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 4,377