Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Balance beginning	$ 36	$ 109	$ 82
Additions based on tax positions related to the current year	5	6	19
Additions based on tax positions of prior years		12	11
Accrued interest	2	2	4
Settlements		(88)	(1)
Lapse of statute of limitations	(3)	(5)	(6)
Balance ending	40	$ 36	$ 109
Net unrecognized tax benefits that would impact effective tax rate	$ 33