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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Description of significant modifications (such as a change in expiration dating, vesting rights, or exercise prices) to an equity-based compensation plan, including the terms of the modifications.

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Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stock-Based Compensation (Additional Information) (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) target $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Description and Terms	The options are generally exercisable 36 months after being granted and have a maximum term of 10 years.
Shares available for future grants under the PPG Omnibus Plan \| shares	7.8
Stock-based compensation expense \| $	$ 37	$ 35	$ 45
Total income tax benefit recognized related to the stock-based compensation \| $	$ 8	$ 12	$ 17
Maximum term of the outstanding stock options for the PPG Omnibus Plan and the PPG Stock Plan for certain employees	10 years
Weighted average fair value of options granted (in dollars per share) \| $ / shares	$ 25.27	$ 21.15	$ 17.94
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	36 months
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost that have not yet vested \| $	$ 7
Cost not yet recognized, period for recognition	1 year 6 months
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost that have not yet vested \| $	$ 17
Cost not yet recognized, period for recognition	1 year 9 months 18 days
Award vesting period	3 years
Restricted Stock Units (RSUs) \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of the target award that is paid based on performance	0.00%	0.00%	0.00%
Restricted Stock Units (RSUs) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of the target award that is paid based on performance	180.00%	180.00%	180.00%
Restricted Stock Units (RSUs) \| Performance Period Twenty Thirteen To Twenty Fifteen [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of the target award that is assumed to vest for the purposes of expense recognition	100.00%
Restricted Stock Units (RSUs) \| Performance Period 2017 to 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance targets met	2
Number of performance targets	4
Restricted Stock Units (RSUs) \| Performance Period 2018 to 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance targets met	1
Number of performance targets	2
Restricted Stock Units (RSUs) \| Performance Period 2016 to 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance targets met	3
Number of performance targets	6
Contingent Share Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost that have not yet vested \| $	$ 5
Cost not yet recognized, period for recognition	1 year 9 months 18 days		3 years
Award vesting period	3 years	3 years
Earned payout if the target performance is achieved	100.00%
Contingent Share Grants \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of the target award that is paid based on performance	0.00%	0.00%	0.00%
Contingent Share Grants \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of the target award that is paid based on performance	220.00%	220.00%	220.00%