Income Taxes - Reconciliation of Uncertain Tax Positions (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits
Unrecognized tax positions, beginning balance	$ 477	$ 495	$ 389
Additions for tax positions related to the current year	37	35	80
Additions for tax positions of prior years	17	22	89
Reductions for tax positions of prior years	(2)	(2)	(13)
Settlements with taxing authorities	(5)	(1)	(2)
Lapse of statute of limitations	(41)	(44)	(48)
Reclassification to indemnification liability related to MAKS divestiture	0	(28)	0
Unrecognized tax positions, ending balance	$ 483	$ 477	$ 495