REVENUE FROM CONTRACTS WITH CUSTOMERS

Contract Balances

Contract assets primarily relate to our rights to consideration for completed performance obligations that are not billable at the reporting date. We recognize contract assets in situations where revenue recognition occurs prior to billing the customer based on our rights under the contract. Contract assets are transferred to accounts receivable when the rights become unconditional, which is generally upon billing.

Contract liabilities primarily relate to consideration received from customers in advance of completing the performance obligation. We recognize contract liabilities under these arrangements as revenue once all contingencies or potential performance obligations have been satisfied by either the (i) transportation of volumes, (ii) performance of terminalling and storage services, or (iii) expiration of the customer’s rights under the contract. We also recognize contract liabilities in revenue to the extent it is determined that an amount of volume associated with a minimum volume commitment payment will not be shipped by the customer in a future period.

The following table provides information about receivables from contracts with customers, contract assets and contract liabilities (in thousands):



	December 31, 2018			December 31, 2017
Receivables from contracts with customers	$	199,324		$	245,280
Contract assets	16,989			13,999
Contract liabilities	(26,999		)	(15,778		)

During the year ended December 31, 2018, we reclassified approximately $14.0 million of contract assets at the beginning of the period to receivables as a result of the rights to the consideration becoming unconditional and billable. Revenue recognized during the year ended December 31, 2018 from amounts included in contract liabilities at the beginning of the period was approximately $8.2 million.

The following table includes estimated revenue associated with contractual commitments in place related to future performance obligations as of the end of the reporting period, which are expected to be recognized in revenue in the specified periods (in thousands):



	Estimated Revenue ⁽¹⁾
2019	$	358,060
2020	196,399
2021	126,777
2022	51,499
Thereafter	212,374
Total	$	945,109


(1)	Excludes revenue arrangements accounted for as leases in the amount of $211.7 million for 2019, $207.2 million for 2020, $188.0 million for 2021, $134.8 million for 2022, and $48.5 million thereafter.

Our contractually committed revenue disclosure, for purposes of the tabular presentation above, excludes estimates of variable rate escalation clauses in our contracts with customers and is generally limited to our contracts fixed pricing and minimum volume components. Our contractually committed revenue disclosure generally excludes remaining performance obligations on contracts with index-based pricing or variable volume attributes.