Note 9. Revenues

We classify our revenues into sales of products and midstream services. Product sales relate primarily to our various marketing activities whereas midstream services represent our other integrated businesses (i.e., processing, fractionation, transportation, storage and terminaling). The following table presents our revenues by business segment, and further by revenue type, for the periods indicated:

	For the Three Months Ended March 31,
	2019		2018
NGL Pipelines & Services:
Sales of NGLs and related products	$	2,671.2	$	2,815.4
Segment midstream services:
Natural gas processing and fractionation		269.5		252.4
Transportation		275.3		255.5
Storage and terminals		98.4		90.0
Total segment midstream services		643.2		597.9
Total NGL Pipelines & Services		3,314.4		3,413.3
Crude Oil Pipelines & Services:
Sales of crude oil		2,328.4		3,341.7
Segment midstream services:
Transportation		183.7		141.7
Storage and terminals		95.2		87.5
Total segment midstream services		278.9		229.2
Total Crude Oil Pipelines & Services		2,607.3		3,570.9
Natural Gas Pipelines & Services:
Sales of natural gas		655.7		560.0
Segment midstream services:
Transportation		271.8		244.8
Total segment midstream services		271.8		244.8
Total Natural Gas Pipelines & Services		927.5		804.8
Petrochemical & Refined Products Services:
Sales of petrochemicals and refined products		1,480.6		1,289.3
Segment midstream services:
Fractionation and isomerization		40.8		55.7
Transportation, including marine logistics		126.6		119.6
Storage and terminals		46.3		44.9
Total segment midstream services		213.7		220.2
Total Petrochemical & Refined Products Services		1,694.3		1,509.5
Total consolidated revenues	$	8,543.5	$	9,298.5

Substantially all of our revenues are derived from contracts with customers. In total, product sales and midstream services accounted for 84% and 16%, respectively, of our consolidated revenues for the three months ended March 31, 2019. During the three months ended March 31, 2018, product sales and midstream services accounted for 86% and 14%, respectively, of our consolidated revenues.

Unbilled Revenue and Deferred Revenue

The following table provides information regarding our contract assets and contract liabilities at March 31, 2019:

Contract Asset	Location	Balance
Unbilled revenue (current amount)	Prepaid and other current assets	$	73.7
Total		$	73.7

Contract Liability	Location	Balance
Deferred revenue (current amount)	Other current liabilities	$	83.0
Deferred revenue (noncurrent)	Other long-term liabilities		218.1
Total		$	301.1

The following table presents significant changes in our unbilled revenue and deferred revenue balances during the three months ended March 31, 2019:

	Unbilled Revenue			Deferred Revenue
Balance at December 31, 2018	$	13.3		$	291.2
Amount included in opening balance transferred to other accounts during period (1)		(0.3	)		(56.8	)
Amount recorded during period		70.1			118.1
Amounts recorded during period transferred to other accounts (1)		(9.4	)		(48.1	)
Other changes		--			(3.3	)
Balance at March 31, 2019	$	73.7		$	301.1

(1)Unbilled revenues are transferred to accounts receivable once we have an unconditional right to consideration from the customer. Deferred revenues are recognized as revenue upon satisfaction of our performance obligation to the customer.

Remaining Performance Obligations

The following table presents estimated fixed future consideration from contracts with customers as of March 31, 2019 that contain minimum volume commitments, deficiency and similar fees, and contract terms exceeding one year.

Remainder of 2019				2020				2021				2022				2023				Thereafter				Total
$	2,826.5			$	3,437.0			$	2,812.0			$	2,295.9			$	1,946.8			$	8,304.6			$	21,622.8