Share-Based Compensation (Details) (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Share-Based Compensation
Share-based compensation expense	$ 9	$ 10	$ 21	$ 20
Share-based awards, stock options, granted			1.0	1.1
Share-based awards, restricted stock units, granted			0.3	0.4
Share-based awards, stock options, weighted-average estimated fair values			$ 22.69	$ 17.46
Share-based awards, restricted stock units, weighted-average estimated fair values			$ 61.74	$ 47.77
Share-based awards, stock options, exercised			1.1	0.9