Income Taxes (Reconciliation of Statutory U.S. Corporate Federal Income Tax Rate to Effective Income Tax Rate) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S. federal income tax rate	35.00%	35.00%	35.00%
Changes in rate due to:
U.S. tax benefit on foreign dividends	(3.80%)	(3.30%)	(1.90%)
U.S. State and local taxes	0.90%	0.60%	0.50%
Taxes on foreign earnings	(8.70%)	(7.40%)	(10.60%)
PPG dividends paid to the ESOP	(0.40%)	(0.40%)	(0.20%)
U.S. tax incentives	(2.20%)	(2.80%)	(2.40%)
Other	(2.60%)	(1.10%)	(2.50%)
Effective income tax rate	18.20%	20.60%	17.90%