Share Repurchases (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 18, 2011	Jul. 31, 2011	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Share Repurchases [Abstract]
Repurchase of outstanding ordinary shares, authorized, value	$ 200.0
Share repurchase aggregate limit percentage of its ordinary shares outstanding		10.00%
Purchase price of stock repurchased and retired during period				415.8
Stock retired during the period			23.5
Stock repurchased and retired during period, shares				66.9
Shares available to be repurchased under the plans				35
Stock repurchased during period, shares					60.9
Purchase price of stock repurchased during period					$ 368.0