Shareholders' Equity (details) - Repurchases (Board of Directors Approved Repurchase Authorizations [Member], USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Board of Directors Approved Repurchase Authorizations [Member]
Repurchase activity
Number of shares repurchased (in shares)	3.6	7.3
Cost of shares repurchased	$ 300,000,000	$ 600,000,000
Average cost per share	$ 82.99	$ 81.99
Remaining capacity under share repurchase authorization		$ 1,560,000,000