Investment in Unconsolidated Affiliate (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Equity Method Investments [Line Items]
Beginning of period	$ 55.9
Equity earnings	4.9		1.6
End of period	53.7
Return of capital from unconsolidated affiliate	2.2		0
Gulf Coast Fractionators LP [Member]
Equity Method Investments [Line Items]
Ownership interest percentage (in hundredths)	38.80%
Beginning of period	55.9
Equity earnings	4.9
Cash distributions	(7.1)	[1]
End of period	$ 53.7

[1] Includes distributions in excess of cumulative earnings of $2.2 million that are considered a return of capital and disclosed in cash flows from investing activities in the Consolidated Statements of Cash Flows.