Fair Value Measurements Fair Value and Related Carrying Amount of Certain Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 1,038.3	$ 376.1	$ 445.6	$ 1,160.1
Checks outstanding in excess of cash balances	0.0	29.8
Long-term debt	2,194.6	2,191.5
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	1,038.3	376.1
Checks outstanding in excess of cash balances	0.0	29.8
Long-term debt	2,194.6	2,191.5
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	1,038.3	376.1
Checks outstanding in excess of cash balances	0.0	29.8
Long-term debt, fair value	$ 2,150.1	$ 1,784.6