Fair Value Measurements Fair Value and Related Carrying Amount of Certain Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 178.8	$ 443.8
Checks outstanding in excess of cash balances	11.9	12.3
Long-term debt	2,023.0	2,020.9
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	178.8	443.8
Checks outstanding in excess of cash balances	11.9	12.3
Long-term debt, fair value	$ 2,036.4	$ 2,104.3