Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Reportable Segment Information (Additional Information) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 Segment
Segment Reporting Information [Line Items]
Number of Operating Segments			11
Pittsburgh Glass Works LLC [Member]
Segment Reporting Information [Line Items]
PPG percent ownership interest	38.00%		38.00%
Canadian Pension Plans [Member]
Segment Reporting Information [Line Items]
Pension Settlement Charge, Canadian wind-up \| $	$ 7	$ 2