Share Capital (Movements in Treasury Shares) (Details) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Beginning balance	66.8	59.2	54.0
Acquisition of common shares	9.5	16.3	13.2
Distribution of common shares	(5.8)	(7.2)	(6.3)
Common shares distributed to meet ESPP obligation	(0.2)	0	0
Common shares distributed to meet option exercises	(0.9)	(1.5)	(1.7)
Ending balance	69.4	66.8	59.2