Inventories (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Inventory amounts by product type [Abstract]
NGLs	$ 563.6		$ 548.3
Petrochemicals and refined products	443.4		399.7
Crude oil	39.2		121.1
Natural gas	65.5		64.7
Other	0		0.2
Total	1,111.7		1,134.0
Summary of cost of sales and lower of cost or market adjustments [Abstract]
Cost of sales	38,292.6	[1]	28,761.6	[1]	20,921.8	[1]
Lower of cost or market adjustments	$ 9.5		$ 7.9		$ 6.3

[1] Cost of sales is a component of "Operating costs and expenses," as presented on our Statements of Consolidated Operations. Year-to-year fluctuations in these amounts are primarily due to changes in energy commodity prices and sales volumes associated with our marketing activities.