Stock-based Compensation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation [Abstract]
RSUs and PSUs	$ 35	$ 35	$ 73	$ 69
Stock options and equivalents	8	9	16	15
Stock-based compensation expense, before income taxes	43	44	89	84
Related tax benefit	(16)	(17)	(34)	(33)
Stock-based compensation expense, net of tax	27	$ 27	$ 55	$ 51
Number of RSUs granted during the period			3
Weighted average grant date fair value - RSUs			$ 59.18
Number of stock options granted during the period			2
Weighted average per unit exercise price - options			$ 59.60
Unrecognized future expense of RSUs	271		$ 271
Unrecognized future expense of stock options	$ 66		$ 66
Term until expiration - options			8 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period over which grants vest			4 years
Weighted average period to expense unrecognized stock-based compensation expense			2 years 9 months 18 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period to expense unrecognized stock-based compensation expense			2 years 7 months 6 days
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout on stock-based compensation award (percent)			120.00%
Service period over which grants vest			4 years
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout on stock-based compensation award (percent)			0.00%
Service period over which grants vest			1 year