Debt (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 4.625% Senior Notes due November 30, 2019 [Member]	Dec. 31, 2010 4.625% Senior Notes due November 30, 2019 [Member]	Nov. 30, 2009 4.625% Senior Notes due November 30, 2019 [Member]	Dec. 31, 2011 5.75% Senior Notes due November 30, 2039 [Member]	Dec. 31, 2010 5.75% Senior Notes due November 30, 2039 [Member]	Nov. 30, 2009 5.75% Senior Notes due November 30, 2039 [Member]	Dec. 31, 2011 1.4% Senior Notes due November 30, 2014 [Member]	Nov. 30, 2011 1.4% Senior Notes due November 30, 2014 [Member]	Dec. 31, 2010 1.4% Senior Notes due November 30, 2014 [Member]	Dec. 31, 2011 3.375% Senior Notes due November 30, 2021 [Member]	Nov. 30, 2011 3.375% Senior Notes due November 30, 2021 [Member]	Dec. 31, 2010 3.375% Senior Notes due November 30, 2021 [Member]	Dec. 31, 2011 Senior Notes [Member]	Dec. 31, 2010 Senior Notes [Member]
Short-term Debt
Senior Credit Facility	$ 143.0	$ 0
Other short-term debt	0.3	0
Total short-term debt	143.3	0
Long term debt
Senior notes due			500.0	500.0	500.0	500.0	500.0	500.0	250.0	250.0	0	300.0	300.0	0
Debt discount															(1.8)	(1.2)
Adjustment related to interest rate swaps	27.8	1.5
Senior Credit Facility	0	141.8
Total long-term debt	$ 1,576.0	$ 1,142.1