Employee Benefit Plans (Employee Savings Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Company-matching contributions are applied to eligible participant compensation	6.00%
Compensation expense related to the ESOP	$ 46	$ 48	$ 44
Deductible dividends on PPG shares held by the ESOP	$ 14	$ 14	$ 13
Minimum
Company-matching contribution	2.00%
Maximum
Company-matching contribution	5.00%