Employee Benefit Plans (Other Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined contribution plan contribution rates as percentage of employee earnings	6.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Compensation expense related to the ESOP	$ 52	$ 50	$ 49
Deductible dividends on PPG shares held by the ESOP	10	11	11
Recognized expense for defined contribution pension plans	88	64	70
Expense (income) of the deferred compensation plan	20	25	21
Increase (Decrease) in fair value of investments	18	24	$ 20
Obligations under the deferred compensation plan	139	138
Investments in marketable securities by the deferred compensation plan	$ 104	$ 103