Revenue Recognition

The following table disaggregates revenues by type within each of our business segments:



	Three Months Ended March 31,
	2019		2018
Gaming
Gaming operations	$	152	$	161
Gaming machine sales	136		145
Gaming systems	74		75
Table products	60		62
Total	$	422	$	443

Lottery
Instant products	$	140	$	150
Lottery systems	87		52
Total	$	227	$	202

Social
Mobile	$	97	$	73
Web and other	21		24
Total	$	118	$	97

Digital
Sports and platform	$	30	$	26
Gaming and other	40		44
Total	$	70	$	70

The amount of rental income revenue that is outside the scope of ASC 606 was $96 million and $67 million for the three months ended March 31, 2019 and 2018, respectively.

Contract Liabilities and Other Disclosures

The following table summarizes the activity in our contract liabilities for the reporting period:



	Three Months Ended March 31,
	2019
Contract liability balance, beginning of period⁽¹⁾	$	97
Liabilities recognized during the period	26
Amounts recognized in revenue from beginning balance	(22		)
Contract liability balance, end of period⁽¹⁾	$	101
(1) Contract liabilities are included within Accrued liabilities and Other long-term liabilities in our March 31, 2019 consolidated balance sheet.

The timing of revenue recognition, billings and cash collections results in billed receivables, unbilled receivables (contract assets), and customer advances and deposits (contract liabilities) on our consolidated balance sheet. Other than contracts with customers with financing arrangements exceeding 12 months, revenue recognition is generally proximal to conversion to cash, except for Lottery instant products sold under POS contracts. Revenue is recognized for such contracts upon delivery to our customers, while conversion to cash is based on the retail sale of the underlying ticket to end consumers. As a result, revenue recognition under ASC 606 does not approximate conversion to cash in any periods post-adoption. Total revenue recognized under such contracts was $23 million and $34 million in the three months ended March 31, 2019 and 2018, respectively. The following table summarizes our balances in these accounts for the periods indicated (other than contract liabilities disclosed above):



	Receivables		Contract Assets⁽¹⁾
Beginning of period balance	$	753	$	114
End of period balance, March 31, 2019	758		114
(1) Contract assets are included primarily within Prepaid expenses, deposits and other current assets in our March 31, 2019 consolidated balance sheet.

As of March 31, 2019, we did not have material unsatisfied performance obligations for contracts expected to be long-term or contracts for which we recognize revenue at an amount other than for which we have the right to invoice for goods or services delivered or performed.