Income Taxes - U.S. and International Components of Income before Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
U.S.																	$ 704	$ 882	$ 658
International																	(198)	(338)	276
Income before income taxes	$ 451	[1]	$ (43)	[1]	$ 17	[1]	$ 81	[1]	$ 337	[1]	$ (22)	[1]	$ 146	[1]	$ 84	[1]	$ 506	$ 544	$ 934

[1] The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is due to the effects of rounding and changes in the number of weighted-average shares outstanding for each period.