Common Stock - Stock Options Activity (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Number of Stock Options
Stock Options outstanding, January 1, 2013 (in shares)	3,341,529
Granted (in shares)	791,760
Exercised (in shares)	(788,982)
Forfeited (in shares)	(38,010)
Stock Options outstanding, December 31, 2013 (in shares)	3,306,297
Stock Options exercisable, December 31, 2013 (in shares)	2,214,272
Wtd. Avg. Exercise Price Per Share
Stock Options outstanding, January 1, 2013 (in dollars per share)	$ 47.03
Granted (in dollars per share)	$ 77.34
Exercised (in dollars per share)	$ 35.92
Forfeited (in dollars per share)	$ 68.07
Stock Options outstanding, December 31, 2013 (in dollars per share)	$ 56.70
Stock Options exercisable, December 31, 2013 (in dollars per share)	$ 47.83
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term, options outstanding	5 years 10 months 10 days
Weighted average remaining contractual term, options exercisable	4 years 4 months 28 days
Aggregate intrinsic value, options outstanding	$ 123
Aggregate intrinsic value, options exercisable	$ 102