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, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S.																	$ 292	$ 704	$ 882
International																	(403)	(198)	(338)
Income (loss) before income taxes	$ 429	[1]	$ (634)	[1]	$ (27)	[1]	$ 120	[1]	$ 451	[1]	$ (43)	[1]	$ 17	[1]	$ 81	[1]	$ (111)	$ 506	$ 544

[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.