Reportable Business Segment Information (Reportable Segment Information) (Detail) - Segment	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Number of PPG operating segments		10
Number of PPG reportable business segments, based on economic similarities, the nature of their products, production processes, end-use markets and methods of distribution		2
Scenario, Forecast
Segment Reporting Information [Line Items]
Number of PPG operating segments	9