Discontinued operations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Discontinued operations
Net sales of divested operations				$ 156.0
Proceeds from sale of discontinued operations	0	0	75.2
Income from discontinued operations, net of tax	0	0	1.8
Alcan Packaging Food Americas Disposal Group [Member]
Discontinued operations
Number of facilities divested			2
Net sales of divested operations			55.0
Proceeds from sale of discontinued operations			75.2
Income before income taxes of divested operations			2.8
Provision for income taxes of divested operations			(1.0)
Income from discontinued operations, net of tax			$ 1.8