Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 6.3	$ 9.3
Preferred shares - par value	$ 0	$ 0
Preferred shares - without par value, authorized	5.0	5.0
Preferred shares - without par value, outstanding	0	0
Common shares - par value	$ 0	$ 0
Common shares - without par value, authorized	500.0	500.0
Common shares - without par value, issued	186.8	185.0
Common shares - without par value, outstanding	112.5	115.4
Treasury stock - shares	74.3	69.6