Fair Value Measurements Fair Value Measurements - Fair Value and Related Carrying Amount of Certain Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 0	$ 11.9	$ 123.0	$ 0
Checks outstanding in excess of cash balances	36.8	109.1
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	3,209.3	3,034.9
Cash and Cash Equivalents, at Carrying Value	0	11.9
Checks outstanding in excess of cash balances	36.8	109.1
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	3,115.5	2,997.5
Cash and Cash Equivalents, at Carrying Value	0	11.9
Checks outstanding in excess of cash balances	$ 36.8	$ 109.1