Gain (loss) on sales or impairment of long lived assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairment Charges									$ (4.4)	$ (74.0)	$ (2.4)
Gain (Loss) on Sale of Property Plant Equipment									(0.5)	0.1	0
Gain Loss On Sale Or Impairment Of Long Lived Assets, Net	(0.4)	(4.3)	(0.1)	(0.1)	(0.9)	(65.0)	(2.5)	(5.5)	(4.9)	(73.9)	(2.4)
Houlton [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairment Charges										(62.0)
held and used or held for sale [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairment Charges										(12.0)	(1.5)
Roads [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairment Charges											(0.9)
Fair Value, Inputs, Level 2 [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Gain Loss On Sale Or Impairment Of Long Lived Assets, Net											(0.9)
Impairment of Long-Lived Assets to be Disposed of									$ 4.4	$ 6.9