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	$ 800
2013 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	475
2014 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	277
2015 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	88
2016 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	2
2017 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	2
2018 - 2028 [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	4
Total [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 848