Stock-Based Compensation (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 30	$ 26	$ 48	$ 47
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	6	4	9	6
Granted (in shares)					0.8
Granted (in dollars per share)					$ 23.38
Unrecognized compensation expense	21		21
Unrecognized compensation expense, period for recognition			2 years 6 months
Restricted stock and unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	24	22	39	41
Granted (in shares)					0.7
Granted (in dollars per share)					$ 77.67
Unrecognized compensation expense	$ 101		$ 101
Unrecognized compensation expense, period for recognition			1 year 9 months 18 days