Earnings Per Common Share (Additional Detail) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings per common share (attributable to PPG)
Income from continuing operations, net of tax	$ 295	$ 366	$ 270	$ 312	$ 256	$ 368	$ 371	$ 328	$ 1,243	$ 1,323	$ 1,369
Income from discontinued operations, net of tax	(3)	1	2	0	2	10	0	6	0	18	225
Net income (attributable to PPG)	$ 292	$ 367	$ 272	$ 312	$ 258	$ 378	$ 371	$ 334	$ 1,243	$ 1,341	$ 1,594
Weighted average common shares outstanding									236.9	243.9	256.1
Effect of dilutive securities:
Stock options									0.6	0.8	0.9
Other stock compensation plans									0.7	0.7	0.8
Potentially dilutive common shares									1.3	1.5	1.7
Adjusted weighted average common shares outstanding									238.2	245.4	257.8
Earnings per common share (attributable to PPG):
Continuing operations (in dollars per share)	$ 1.24	$ 1.55	$ 1.14	$ 1.32	$ 1.07	$ 1.52	$ 1.51	$ 1.32	$ 5.25	$ 5.43	$ 5.34
Discontinued operations (in dollars per share)	(0.01)	0	0.01	0	0.01	0.04	0	0.02	0	0.07	0.88
Net Income (attributable to PPG) (in dollars per share)	1.23	1.55	1.15	1.32	1.08	1.56	1.51	1.34	5.25	5.50	6.22
Earnings per common share - assuming dilution (attributable to PPG)
Continuing operations (in dollars per share)	1.23	1.54	1.13	1.31	1.07	1.51	1.51	1.31	5.22	5.40	5.31
Discontinued operations (in dollars per share)	(0.01)	0	0.01	0	0.01	0.04	0	0.02	0	0.07	0.87
Earnings per common share - assuming dilution (in dollars per share)	$ 1.22	$ 1.54	$ 1.14	$ 1.31	$ 1.08	$ 1.55	$ 1.51	$ 1.33	$ 5.22	$ 5.47	$ 6.18
Outstanding stock options excluded from the computation of diluted earnings per share due to their antidilutive effect									0.9	1.0	0.6