Fair Value Measurements Fair Value on a Nonrecurring Basis (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
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	1,610.4	1,566.0
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Total long-term debt	77.3	80.4
Fair Value, Total
Fair value assets and liabilities measured on recurring and nonrecurring basis
Total long-term debt	$ 1,687.7	$ 1,646.4