Inventories (Tables)

3 Months Ended

Mar. 31, 2018

Our inventory amounts by product type were as follows at the dates indicated:

	March 31, 2018		December 31, 2017
NGLs	$	922.4	$	917.4
Petrochemicals and refined products		195.7		161.5
Crude oil		571.1		516.3
Natural gas		10.7		14.6
Total	$	1,699.9	$	1,609.8

Cost of Sales and Lower of Cost or Market Adjustments

Due to fluctuating commodity prices, we recognize lower of cost or market adjustments when the carrying value of our available-for-sale inventories exceeds their net realizable value. The following table presents our total cost of sales amounts and lower of cost or net realizable value adjustments for the periods indicated:

	For the Three Months Ended March 31,
	2018		2017
Cost of sales (1)	$	7,140.4	$	5,335.7
Lower of cost or net realizable value adjustments within cost of sales		1.9		3.4

(1) Cost of sales is a component of “Operating costs and expenses” as presented on our Unaudited Condensed 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.