Inventories (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory by Product Type [Abstract]
NGLs		$ 917.4	$ 1,156.1
Petrochemicals and refined products		161.5	220.7
Crude oil		516.3	360.0
Natural gas		14.6	33.7
Total		1,609.8	1,770.5
Summary of cost of sales and lower of cost or net realizable value adjustments [Abstract]
Cost of sales	[1]	21,487.0	15,710.9	$ 19,612.9
Lower of cost or net realizable value adjustments within cost of sales		$ 9.1	$ 11.5	$ 19.8

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