Shareholders' Equity Schedule of Net Income from Participating Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income from participating securities	$ 3	$ 2	$ 8	$ 8
Continuing Operations [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income from participating securities	3	2	8	8
Discontinued Operations [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income from participating securities	$ 0	$ 0	$ 0	$ 0