We disaggregate our revenues by segment and type of activity under ASC Topic 606, Revenues from Contracts with Customers (“Topic 606”). These categories depict how the nature, amount, timing and uncertainty of revenues and cash flows are affected by economic factors. See Note 3 to our Consolidated Financial Statements included in Part IV of our 2018 Annual Report on Form 10-K for additional information regarding our types of revenues and policies for revenue recognition.



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Supply and Logistics segment revenues from contracts with customers
Crude oil transactions	$	7,595	$	7,649	$	14,532	$	14,672
NGL and other transactions	269		475		1,178		1,626
Total Supply and Logistics segment revenues from contracts with customers	$	7,864	$	8,124	$	15,710	$	16,298



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Transportation segment revenues from contracts with customers
Tariff activities:
Crude oil pipelines	$	494	$	412	$	971	$	801
NGL pipelines	22		24		50		51
Total tariff activities	516		436		1,021		852
Trucking	35		34		74		68
Total Transportation segment revenues from contracts with customers	$	551	$	470	$	1,095	$	920



	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Facilities segment revenues from contracts with customers
Crude oil, NGL and other terminalling and storage	$	177	$	171	$	349	$	337
NGL and natural gas processing and fractionation	87		91		175		191
Rail load / unload	19		16		39		32
Total Facilities segment revenues from contracts with customers	$	283	$	278	$	563	$	560

Reconciliation to Total Revenues of Reportable Segments. The following table presents the reconciliation of our revenues from contracts with customers to segment revenues and total revenues as disclosed in our Condensed Consolidated Statements of Operations (in millions):



Three Months Ended June 30, 2019	Transportation		Facilities		Supply and Logistics		Total
Revenues from contracts with customers	$	551	$	283	$	7,864	$	8,698
Other items in revenues	8		8		51		67
Total revenues of reportable segments	$	559	$	291	$	7,915	$	8,765
Intersegment revenues							(512		)
Total revenues							$	8,253



Three Months Ended June 30, 2018	Transportation		Facilities		Supply and Logistics			Total
Revenues from contracts with customers	$	470	$	278	$	8,124		$	8,872
Other items in revenues	5		6		(343		)	(332		)
Total revenues of reportable segments	$	475	$	284	$	7,781		$	8,540
Intersegment revenues								(460		)
Total revenues								$	8,080



Six Months Ended June 30, 2019	Transportation		Facilities		Supply and Logistics		Total
Revenues from contracts with customers	$	1,095	$	563	$	15,710	$	17,368
Other items in revenues	20		26		228		274
Total revenues of reportable segments	$	1,115	$	589	$	15,938	$	17,642
Intersegment revenues							(1,014		)
Total revenues							$	16,628



Six Months Ended June 30, 2018	Transportation		Facilities		Supply and Logistics			Total
Revenues from contracts with customers	$	920	$	560	$	16,298		$	17,778
Other items in revenues	9		16		(405		)	(380		)
Total revenues of reportable segments	$	929	$	576	$	15,893		$	17,398
Intersegment revenues								(920		)
Total revenues								$	16,478

Minimum Volume Commitments. We have certain agreements that require counterparties to transport or throughput a minimum volume over an agreed upon period. At June 30, 2019 and December 31, 2018, counterparty deficiencies associated with contracts with customers and buy/sell arrangements that include minimum volume commitments totaled $54 million and $62 million, respectively, of which $35 million and $40 million, respectively, was recorded as a contract liability. The remaining balance of $19 million and $22 million at June 30, 2019 and December 31, 2018, respectively, was related to deficiencies for which the counterparties had not met their contractual minimum commitments and were not reflected in our Condensed Consolidated Financial Statements as we had not yet billed or collected such amounts.

Contract Balances. Our contract balances consist of amounts received associated with services or sales for which we have not yet completed the related performance obligation. The following table presents the change in the contract liability balance during the six months ended June 30, 2019 (in millions):

Remaining Performance Obligations. Topic 606 requires a presentation of information about partially and wholly unsatisfied performance obligations under contracts that exist as of the end of the period. The information includes the amount of consideration allocated to those remaining performance obligations and the timing of revenue recognition of those remaining performance obligations. Certain contracts meet the requirements for the presentation as remaining performance obligations. These arrangements include a fixed minimum level of service, typically a set volume of service, and do not contain any variability other than expected timing within a limited range. These contracts are all within the scope of Topic 606. The following table presents the amount of consideration associated with remaining performance obligations for the population of contracts with external customers meeting the presentation requirements as of June 30, 2019 (in millions):



	Remainder of 2019		2020		2021		2022		2023		2024 and Thereafter
Pipeline revenues supported by minimum volume commitments and capacity agreements ⁽¹⁾	$	79	$	156	$	163	$	159	$	158	$	805
Storage, terminalling and throughput agreement revenues	220		361		256		195		160		355
Total	$	299	$	517	$	419	$	354	$	318	$	1,160

The presentation above does not include (i) expected revenues from legacy shippers not underpinned by minimum volume commitments, including pipelines where there are no or limited alternative pipeline transportation options, (ii) intersegment revenues and (iii) the amount of consideration associated with certain income generating contracts, which include a fixed minimum level of service, that are either not within the scope of Topic 606 or do not meet the requirements for presentation as remaining performance obligations under Topic 606. The following are examples of contracts that are not included in the table above because they are not within the scope of Topic 606 or do not meet the Topic 606 requirements for presentation:

Our accounts receivable are primarily from purchasers and shippers of crude oil and, to a lesser extent, purchasers of NGL. To mitigate credit risk related to our accounts receivable, we utilize a rigorous credit review process. We closely monitor market conditions and perform credit reviews of each customer to make a determination with respect to the amount, if any, of open credit to be extended to any given customer and the form and amount of financial performance assurances we require. Such financial assurances are commonly provided to us in the form of advance cash payments, standby letters of credit, credit insurance or parental guarantees. Additionally, in an effort to mitigate credit risk, a significant portion of our transactions with counterparties are settled on a net-cash basis. For a majority of these net-cash arrangements, we also enter into netting agreements (contractual agreements that allow us to offset receivables and payables with those counterparties against each other on our balance sheet).

Accounts receivable from the sale of crude oil are generally settled with counterparties on the industry settlement date, which is typically in the month following the month in which the title transfers. Otherwise, we generally invoice customers within 30 days of when the products or services were provided and generally require payment within 30 days of the invoice date. We review all outstanding accounts receivable balances on a monthly basis and record a reserve for amounts that we expect will not be fully recovered. We do not apply actual balances against the reserve until we have exhausted substantially all collection efforts. At June 30, 2019 and December 31, 2018, substantially all of our trade accounts receivable (net of allowance for doubtful accounts) were less than 30 days past their scheduled invoice date. Our allowance for doubtful accounts receivable totaled $3 million at both June 30, 2019 and December 31, 2018. Although we consider our allowance for doubtful accounts receivable to be adequate, actual amounts could vary significantly from estimated amounts.

The following is a reconciliation of trade accounts receivable from revenues from contracts with customers to total Trade accounts receivable and other receivables, net as presented on our Condensed Consolidated Balance Sheets (in millions):



	June 30, 2019			December 31, 2018
Trade accounts receivable arising from revenues from contracts with customers	$	2,563		$	2,277
Other trade accounts receivables and other receivables ⁽¹⁾	3,722			2,732
Impact due to contractual rights of offset with counterparties	(3,450		)	(2,555		)
Trade accounts receivable and other receivables, net	$	2,835		$	2,454