Investments (Additional Information) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2000	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jul. 31, 2012 Asian Paints Ltd. [Member]	Dec. 31, 2000 R S Cogen Limited Liability Company [Member]
Variable Interest Entity [Line Items]
PPG percent ownership interest							50.00%
Joint venture formed with a wholly-owned subsidiary of Entergy Corporation for the construction and operation of a process steam, natural gas-fired cogeneration facility	$ 300
Contract term	2022
Disclosure of PPG's future commitment to purchase electricity and steam from the joint venture		PPG’s future commitment to purchase electricity and steam from the joint venture approximates $23 million per year subject to contractually defined inflation adjustments for the next 10 years.
PPG's future commitment to purchase electricity and steam from the joint venture, per year		23	23	23	23
PPG's future commitment to purchase electricity and steam from the joint venture, term in years		10 years
Fair value of tangible assets including goodwill						22
Fair value of intangible assets						12
Noncontrolling interest in joint ventures						$ 48