4. RECEIVABLES, CONTRACT ASSETS, AND DEFERRED REVENUE

Receivables


(in thousands)	June 30, 2018		December 31, 2017
Accounts receivable	$	141,384	$	222,735
Unbilled receivables		151,354		158,898
Long-term unbilled receivables		169,330		160,708

	$	462,068	$	542,341

Unbilled receivables is the amount due from clients where the only condition on the right of payment is the passage of time. The Company regularly assesses receivables for collectability. As of June 30, 2018 and December 31, 2017, the allowance for doubtful accounts was not material.

Unbilled receivables are expected to be billed in the future as follows:


(in thousands)	June 30, 2018
1 Year or Less	$	151,354
1-2 Years		79,654
2-5 Years		89,676

	$	320,684

Contract assets and deferred revenue


(in thousands)	June 30, 2018		December 31, 2017
Contract assets⁽¹⁾	$	2,425	$	914
Long-term contract assets⁽²⁾		1,545		—

	$	3,970	$	914

Deferred revenue	$	163,525	$	166,297
Long-term deferred revenue⁽³⁾		6,210		3,706

	$	169,735	$	170,003

⁽¹⁾ Included in other current assets in the unaudited condensed consolidated balance sheets.

⁽²⁾ Included in other long-term assets in the unaudited condensed consolidated balance sheets.

⁽³⁾ Included in other long-term liabilities in the unaudited condensed consolidated balance sheets.

Contract assets and deferred revenue are presented net at the contract level for each reporting period. Contract assets are amounts under client contracts where revenue recognized exceeds the amount billed to the client and the right to payment is subject to conditions other than the passage of time, such as the completion of a related performance obligation. Deferred revenue consists of billings and payments received in advance of revenue recognition.

The change in deferred revenue in the six months ended June 30, 2018, was primarily due to new billings in advance of revenue recognition and $168.2 million of revenue recognized, excluding the impact of the netting of contract assets and deferred revenue, during the period that was included in deferred revenue at December 31, 2017.

Major clients

No client represented 10% or more of the Company’s total receivables as of June 30, 2018 or December 31, 2017.