12.Unearned Revenue

Changes in unearned revenue were as follows for the three months ended March 31, 2020 and 2019:


	Three Months Ended
	March 31,
(in thousands)	2020		2019
Balance, beginning of period	$	118,211	$	105,837
Billings, excluding billings for customer arrangements with termination rights		40,791		40,323
Additions to unearned revenue upon expiration of termination rights		4,645		5,000
Recognition of revenue, net of change in unbilled accounts receivable*		(49,609)		(48,281)
Balance, end of period	$	114,038	$	102,879

* Reconciliation to Revenue Reported per Condensed Consolidated Statement of Operations:	Three Months Ended
	March 31,
(in thousands)	2020		2019
Revenue billed as of the end of period	$	49,609	$	48,281
Increase (decrease) in total unbilled accounts receivable		89		(199)
Revenue Reported in Condensed Consolidated Statement of Operations	$	49,698	$	48,082

Revenue allocated to remaining performance obligations includes unearned revenue plus contractually committed amounts that will be invoiced and recognized as revenue in future periods, but excludes amounts invoiced and not recognized as revenue under customer arrangements that contain termination rights. Remaining performance obligations were $126.0 million as of March 31, 2020, of which we expect to recognize approximately 74% as revenue over the next 12 months and the remainder thereafter.

As of March 31, 2020 and December 31, 2019, the balance of customer arrangements that contain termination rights was $13.5 million and $16.1 million, respectively.