Shareholders' Equity and Dividend Availability (details) - Repurchases (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Repurchase activity
Shares acquired to cover tax withholding costs and exercise costs	$ 58	$ 61	$ 55
Board of Directors Approved Repurchase Authorizations [Member]
Repurchase activity
Number of shares repurchased (in shares)	35.1			9.7	8.1	9.5	7.8
Cost of shares repurchased	3,275			1,000	750	875	650
Average price paid per share	$ 93.27			$ 102.82	$ 92.47	$ 92.67	$ 82.97
Remaining capacity under share repurchase authorization	1,484			1,484	2,484	3,234	4,109
Amended and Restated 2004 Stock Incentive Plan Repurchases [Member]
Repurchase activity
Shares acquired to cover tax withholding costs and exercise costs	$ 58	$ 61