Income Taxes (Additional Information) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) subsidiary jurisdiction	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Income Taxes [Line Items]
Benefit from reversal of existing deferred tax liability on repatriated foreign earnings		$ 22
Expense for global intangible low taxed income		14
Benefit from foreign derived intangible income		$ 14
U.S. federal income tax rate	21.00%	21.00%	21.00%
Deferred income taxes	$ (47)	$ (5)	$ 45
Pension curtailment charges	13	0	0
Income before income taxes of non-US operations	1,362	1,661	1,693
Net operating loss carryforwards	193	182
Deferred Tax Assets, Tax Credit Carryforwards, Other	119	59
Unrecognized tax benefits that would affect the effective tax rate, if recognized	153
Accrued estimated interest and penalties on unrecognized tax benefits	18	17	16
Recognized (income) expense for estimated interest and penalties	2	1	2
Undistributed Earnings of Foreign Subsidiaries	$ 4,100	3,600
Number of taxable jurisdictions | jurisdiction	75
Net tax charge for Tax Cuts and Jobs Act		42
One-time tax on unrepatriated foreign earnings		20
Number of PPG Subsidiaries | subsidiary	290
Income Tax, Potential U.S. Tax Cost for Repatriation of Foreign Earnings	$ 40	32
U.S.
Income Taxes [Line Items]
Deferred income taxes	30	22
Income before income taxes of non-US operations	190	596	571
Non United States
Income Taxes [Line Items]
Income before income taxes of non-US operations	1,172	1,065	$ 1,122
Net Operating Loss, Indefinite Life
Income Taxes [Line Items]
Net operating loss carryforwards	113	157
Net Operating Loss, Expiring Within 20 Years
Income Taxes [Line Items]
Net operating loss carryforwards	$ 80	$ 25