Fair Value Measurements Fair Value on a Nonrecurring Basis (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Total long-term debt	$ 0	$ 0
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Total long-term debt	2,053.9	2,292.4
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Total long-term debt	83.9	90.8
Fair Value, Total
Fair value assets and liabilities measured on recurring and nonrecurring basis
Total long-term debt	$ 2,137.8	$ 2,383.2