Capital Stock (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Jul. 15, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	May. 27, 2014	Apr. 01, 2014	Sep. 18, 2013
Class of Stock [Line Items]
Payments of Ordinary Dividends, Preferred Stock and Preference Stock				$ 0	$ 15
Payments of Ordinary Dividends, Common Stock				$ 32	$ 26
Common Stock, Dividends, Per Share, Declared		$ 0.06	$ 0.05	$ 0.12	$ 0.10
Payments for Repurchase of Common Stock				$ 52	$ 65
Preferred Stock
Class of Stock [Line Items]
Convertible Preferred Stock, Aggregate Shares Issued upon Conversion							27,573,735
Convertible Preferred Stock, Shares Issued upon Conversion							2.7574
Common Stock
Class of Stock [Line Items]
Payments of Ordinary Dividends, Common Stock				$ 32
Stock Repurchase Program, Authorized Amount						$ 450		$ 100
Share Repurchase Program Expiration Date				Dec. 31, 2016
Treasury Stock, Shares, Acquired		1,600,129		1,600,129
Payments for Repurchase of Common Stock		$ 50		$ 50
Treasury Stock Acquired, Average Cost Per Share		$ 31.25		$ 31.25
Dividend Declared [Member] | Common Stock
Class of Stock [Line Items]
Dividends Payable, Date Declared	Jul. 15, 2015
Dividends Payable, Date of Record	Jul. 31, 2015
Dividends Payable, Date to be Paid	Sep. 01, 2015
Common Stock, Dividends, Per Share, Declared	$ 0.06
Dividends, Common Stock, Cash	$ 16
Payments for Share Repurchases Related to Employee Stock Based Compensation [Member] | Common Stock
Class of Stock [Line Items]
Treasury Stock, Shares, Acquired		36,169		75,520
Payments for Repurchase of Common Stock		$ 1		$ 2
Treasury Stock Acquired, Average Cost Per Share		$ 29.00		$ 27.99