Significant Transactions (Share Repurchases) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Significant Transactions
Additional authorized repurchase of common shares	545,496		545,496
Value of common shares repurchased and retired during the period	$ 0.8	$ 5.2	$ 79.8	$ 491.0
Average price per share	$ 600.00	$ 508.00	$ 564.00	$ 497.00
Common Stock
Significant Transactions
Stock Repurchased and Retired During Period, Shares	1,311	10,172	141,535	987,191
Combination One
Significant Transactions
Value of common shares repurchased and retired during the period				81.2
Average price per share				$ 484.00
Combination One | Common Stock
Significant Transactions
Stock Repurchased and Retired During Period, Shares			140,000	167,801
Combination Two | Tender Offer
Significant Transactions
Value of common shares repurchased and retired during the period				$ 408.6
Average price per share				$ 500.00
Combination Two | Common Stock
Significant Transactions
Stock repurchased and retired during period, pursuant of employee benefit Plans, shares			1,535
Combination Two | Common Stock | Tender Offer
Significant Transactions
Stock Repurchased and Retired During Period, Shares				816,829
Combination Three | Common Stock
Significant Transactions
Stock Repurchased and Retired During Period, Shares				2,561