NOTE 4. RECEIVABLES, CONTRACT ASSETS, AND DEFERRED REVENUE


(in thousands)	March 31, 2021		December 31, 2020
Accounts receivable	$	159,324	$	215,827
Unbilled receivables	228,603		207,155
Long-term unbilled receivables	108,048		113,278
	$	495,975	$	536,260

Unbilled receivables are client-committed amounts for which revenue recognition precedes billing, and billing is solely subject to the passage of time.


(Dollars in thousands)	March 31, 2021
1 year or less	$	228,603	68	%
1-2 years	80,688		24	%
2-5 years	27,360		8	%
	$	336,651	100	%


(Dollars in thousands)	March 31, 2021
2021	$	46,625	14	%
2020	163,226		48	%
2019	63,600		19	%
2018	28,885		9	%
2017 and prior	34,315		10	%
	$	336,651	100	%

No client represented 10% or more of the Company’s total receivables as of March 31, 2021 or December 31, 2020.

Contract assets are client-committed amounts for which revenue recognized exceeds the amount billed to the client, and billing is subject to conditions other than the passage of time, such as completing a related performance obligation.


(in thousands)	March 31, 2021		December 31, 2020
Contract assets (1)	$	13,454	$	15,296
Long-term contract assets (2)	7,284		7,777
	$	20,738	$	23,073

(1) Included in other current assets. (2) Included in other long-term assets.

Deferred revenue consists of billings and payments received in advance of revenue recognition.


(in thousands)	March 31, 2021		December 31, 2020
Deferred revenue	$	244,170	$	232,865
Long-term deferred revenue (1)	7,565		8,991
	$	251,735	$	241,856

The change in deferred revenue in the three months ended March 31, 2021 was primarily due to new billings in advance of revenue recognition offset by $107.0 million of revenue recognized that was included in deferred revenue as of December 31, 2020.