Fair Value Measurements Fair Value Measurements - Fair Value and Related Carrying Amount of Certain Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 702.3	$ 11.9	$ 139.7	$ 0
Checks outstanding in excess of cash balances	5.7	90.9
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	3,910.8	2,997.5
Cash and Cash Equivalents, at Carrying Value	702.3	11.9
Checks outstanding in excess of cash balances	5.7	90.9
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	4,064.5	3,034.9
Cash and Cash Equivalents, at Carrying Value	702.3	11.9
Checks outstanding in excess of cash balances	$ 5.7	$ 90.9