Income Taxes - Uncertain Tax Positions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1,	$ 22	$ 20	$ 18
True-up from tax return filings	4	0	0
Increase in unrecognized tax benefits as a result of position taken during the current period	3	2	2
Decrease due to closing of IRS audit	(9)	0	0
Balance as of December 31,	$ 20	$ 22	$ 20