Business Segments - Schedule of Segment Operating Performance Reconciled to Consolidated Amounts (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	$ 334	$ 123	$ 569	$ 474
Intersegment eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	(5)	0	(8)	(8)
Intersegment eliminations | Maximum
Segment Reporting, Revenue Reconciling Item [Line Items]
Rental expense for model units	1	1	1	1
Intersegment eliminations | Billing and Collection Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	$ 5	$ 0	$ 8	$ 8