Income Taxes (Net Deferred Income Tax Assets and Liabilities) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) jurisdiction	Dec. 31, 2017 USD ($)
Income Tax Examination [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 164	$ 173
Number of PPG Subsidiaries	250
Number of taxable jurisdictions | jurisdiction	75
Undistributed Earnings of Foreign Subsidiaries	$ 3,000	3,400
Income Tax, Potential U.S. Tax Cost for Repatriation of Foreign Earnings	19	30
Deferred income tax assets related to
Employee benefits	366	399
Contingent and accrued liabilities	149	164
Operating loss and other carry-forwards	251	221
Inventories	7	6
Property	48	51
Other	82	135
Valuation allowance	(164)	(173)
Total	739	803
Deferred income tax liabilities related to
Property	310	314
Intangibles	545	578
Employee benefits	46	11
Derivatives	1	1
Undistributed foreign earnings	5	24
Other	9	20
Total	916	948
Deferred income tax liabilities – net	$ (177)	$ (145)
Minimum
Income Tax Examination [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2018
Tax Credit Carryforward, Expiration Date	Dec. 31, 2018
Maximum
Income Tax Examination [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2030
Tax Credit Carryforward, Expiration Date	Dec. 31, 2027