Income Taxes - Reconciliation of our Uncertain Tax Positions (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Uncertain tax positions -
Balance January 1	$ 224	$ 112	$ 111
Gross increases in tax positions due to acquisition	0	110	0
Gross increases in tax positions in current period	12	8	6
Gross increases in tax positions in prior period	4	7	2
Gross decreases in tax positions in prior period	(5)	(1)	(2)
Gross decreases - settlements	(12)	(2)	0
Gross decreases - statute of limitations expired	(8)	(10)	(5)
Balance December 31	$ 215	$ 224	$ 112