Fair Value Measurements Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Level 1
Fair value assets and liabilities measured on nonrecurring basis
Total long-term debt	$ 0.0	$ 0.0
Level 2
Fair value assets and liabilities measured on nonrecurring basis
Total long-term debt	1,606.2	1,574.7
Level 3
Fair value assets and liabilities measured on nonrecurring basis
Total long-term debt	45.9	65.4
Fair Value, Total [Member]
Fair value assets and liabilities measured on nonrecurring basis
Total long-term debt	$ 1,652.1	$ 1,640.1