Stock Based Compensation (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Summary of stock option activity and changes during the year
Number of options outstanding, Beginning balance	11,225,725
Options outstanding, Weighted-average exercise price, Beginning balance	$ 72.45
Number of options granted	388,200
Options granted, Weighted-average exercise price	$ 72.79
Number of options exercised	(1,079,008)
Options exercised , Weighted-average exercise price	$ 42.73
Number of Options forfeited/expired	(75,499)
Options forfeited/expired, Weighted-average exercise price	$ 86.62
Number of options outstanding, Ending balance	10,459,418	11,225,725
Options outstanding, Weighted-average exercise price, Ending balance	$ 75.46	$ 72.45
Options outstanding, Aggregate intrinsic value	$ 0
Options outstanding, Weighted Average Contractual Life	4.7
Number of options exercisable	9,011,257
Options exercisable, Weighted Average Exercise price	$ 75.36
Options exercisable, Aggregate intrinsic value	$ 0
Options exercisable, Weighted Average Contractual Life	4.1
Weighted-average grant-date fair value of options granted during 2011	$ 11.48	$ 13.18	$ 12.47