Earnings Per Common Share (Additional Detail) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings per common share (attributable to PPG)
Continuing operations	$ 256	$ 368	$ 371	$ 328	$ 148	$ 393	$ 497	$ 331	$ 1,323	$ 1,369	$ 543
Discontinued operations	2	10	0	6	3	217	(1)	6	18	225	330
Net income (attributable to PPG)	$ 258	$ 378	$ 371	$ 334	$ 151	$ 610	$ 496	$ 337	$ 1,341	$ 1,594	$ 873
Weighted average common shares outstanding									243,900,000	256,100,000	265,600,000
Effect of dilutive securities:
Stock options									800,000	900,000	800,000
Other stock compensation plans									700,000	800,000	1,000,000
Potentially dilutive common shares									1,500,000	1,700,000	1,800,000
Adjusted weighted average common shares outstanding									245,400,000	257,800,000	267,400,000
Earnings per common share (attributable to PPG):
Continuing operations (in dollars per share)	$ 1.07	$ 1.52	$ 1.51	$ 1.32	$ 0.59	$ 1.53	$ 1.93	$ 1.29	$ 5.43	$ 5.34	$ 2.05
Discontinued operations (in dollars per share)	0.01	0.04	0.00	0.02	0.01	0.85	0.00	0.02	0.07	0.88	1.24
Net Income (attributable to PPG) (in dollars per share)	1.08	1.56	1.51	1.34	0.60	2.38	1.93	1.31	5.50	6.22	3.29
Earnings per common share - assuming dilution (attributable to PPG)
Continuing operations (in dollars per share)	1.07	1.51	1.51	1.31	0.58	1.52	1.92	1.28	5.40	5.31	2.04
Discontinued operations (in dollars per share)	0.01	0.04	0.00	0.02	0.01	0.84	0.00	0.02	0.07	0.87	1.23
Earnings per common share - assuming dilution (in dollars per share)	$ 1.08	$ 1.55	$ 1.51	$ 1.33	$ 0.59	$ 2.36	$ 1.92	$ 1.30	$ 5.47	$ 6.18	$ 3.27
Outstanding stock options excluded from the computation of diluted earnings per share due to their antidilutive effect									1,000,000	600,000.0	600,000.0