Income Taxes (Net Deferred Income Tax Assets and Liabilities) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) jurisdiction	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Tax Examination [Line Items]
Valuation Allowances and Reserves, Balance	$ 170				$ 119
Number of PPG Subsidiaries	250
Number of taxable jurisdictions | jurisdiction	75
Undistributed Earnings of Foreign Subsidiaries	$ 3,400				5,300
Income Tax, Potential U.S. Tax Cost for Repatriation of Foreign Earnings	30				350
Deferred income tax assets related to
Employee benefits	399				606
Contingent and accrued liabilities	164				263
Operating loss and other carry-forwards	221				197
Inventories	6				14
Property	51				49
Other	135				100
Valuation allowance	(173)				(119)
Total	803				1,110
Deferred income tax liabilities related to
Property	314				349
Intangibles	578				647
Employee benefits	11				4
Derivatives	1				6
Undistributed foreign earnings	24				189
Other	20				146
Total	948				1,341
Deferred income tax (liabilities) assets – net	$ (145)	$ (445)	$ (390)	$ (400)	(231)
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
Undistributed earnings, permanently reinvested
Income Tax Examination [Line Items]
Undistributed Earnings of Foreign Subsidiaries					$ 3,500