Long-Term Debt (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of Deferred Finance Cost
Balance as of January, 1 2012	$ 98	$ 37	$ 42
Capitalization of debt finance costs	13	84	12
Amortization	(37)	(23)	(17)
Balance as of December, 31 2012	$ 74	$ 98	$ 37