Goodwill - Schedule of Goodwill (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill beginning balance, gross	$ 2,709	$ 2,709
Goodwill ending balance, gross		2,709
Accumulated impairment losses, beginning balance	(2,102)	(2,102)
Accumulated impairment losses, impairment loss		(607)
Accumulated impairment losses, ending balance		(2,709)
Goodwill, beginning balance	607	607
Impairment loss	$ (607)	$ (607)