Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 3.9	$ 11.9	$ 0	$ 0
Cash and Cash Equivalents, Fair Value Disclosure	3.9	11.9
Financial liabilities
Derivative instruments - long-term	2.9	0
Fair Value, Measurements, Recurring [Member]
Financial Assets
Total financial assets	3.9	1.2
Financial liabilities
Total financial liabilities	74.7	26.7
Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member]
Financial Assets
Derivative instruments - short-term	0	0.2
Derivative instruments - long-term	1.1	0.4
Financial liabilities
Derivative instruments - short-term	67.1	24.1
Derivative instruments - long-term	2.9	0.6
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Financial Assets
Derivative instruments - long-term	2.8
Financial liabilities
Derivative instruments - short-term	4.7	2.6
Fair Value, Measurements, Recurring [Member] | Carrying Amount [Member]
Financial liabilities
Checks outstanding in excess of cash balances	78.4	90.9
Long-term debt	3,919.2	2,997.5
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial Assets
Total financial assets	0	0
Financial liabilities
Total financial liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commodity Contract [Member]
Financial Assets
Derivative instruments - short-term	0	0
Derivative instruments - long-term	0	0
Financial liabilities
Derivative instruments - short-term	0	0
Derivative instruments - long-term	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Interest Rate Swap [Member]
Financial Assets
Derivative instruments - long-term	0
Financial liabilities
Derivative instruments - short-term	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Fair Value [Member]
Financial liabilities
Checks outstanding in excess of cash balances	78.4	90.9
Long-term debt	4,018.0	3,034.9
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial Assets
Total financial assets	9.2	6.5
Financial liabilities
Total financial liabilities	80.0	32.0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commodity Contract [Member]
Financial Assets
Derivative instruments - short-term	5.9	5.5
Derivative instruments - long-term	0.5	0.4
Financial liabilities
Derivative instruments - short-term	73.0	29.4
Derivative instruments - long-term	2.3	0.6
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member]
Financial Assets
Derivative instruments - long-term	2.8
Financial liabilities
Derivative instruments - short-term	4.7	2.6
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial Assets
Total financial assets	0	0
Financial liabilities
Total financial liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commodity Contract [Member]
Financial Assets
Derivative instruments - short-term	0	0
Derivative instruments - long-term	0	0
Financial liabilities
Derivative instruments - short-term	0	0
Derivative instruments - long-term	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Interest Rate Swap [Member]
Financial Assets
Derivative instruments - long-term	0
Financial liabilities
Derivative instruments - short-term	0	0
Fair Value, Measurements, Recurring [Member] | Netting Adjustments [Member]
Financial Assets
Total financial assets	(5.3)	(5.3)
Financial liabilities
Total financial liabilities	(5.3)	(5.3)
Fair Value, Measurements, Recurring [Member] | Netting Adjustments [Member] | Commodity Contract [Member]
Financial Assets
Derivative instruments - short-term	(5.9)	(5.3)
Derivative instruments - long-term	0.6	0
Financial liabilities
Derivative instruments - short-term	(5.9)	(5.3)
Derivative instruments - long-term	0.6	0
Fair Value, Measurements, Recurring [Member] | Netting Adjustments [Member] | Interest Rate Swap [Member]
Financial Assets
Derivative instruments - long-term	0
Financial liabilities
Derivative instruments - short-term	$ 0	$ 0