Property and equipment, net (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Property and equipment, net
Land and improvements	$ 168.8	$ 167.7
Buildings	686.0	697.2
Machinery and equipment	2,461.9	2,470.9
Other property and equipment	168.6	170.7
Construction-in-progress	116.0	104.4
Property and equipment	3,601.3	3,610.9
Accumulated depreciation and amortization	(2,314.5)	(2,288.8)
Property and equipment, net	$ 1,286.8	$ 1,322.1