Segment and Geographic Information - Summary of Revenue by Geographic Area (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue (Note 4)	[1]	$ 604	$ 1,560	$ 1,615
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue (Note 4)		302	821	835
United Kingdom
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue (Note 4)		169	466	508
All Other Countries
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue (Note 4)		$ 133	$ 273	$ 272

[1] Our revenue is recognized primarily at a point in time for all reported segments