Fair Value Measurements Impairment losses (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
Schedule of Available-for-sale Securities [Line Items]
Asset Impairment Charges									$ 4.4	$ 74.0	$ 2.4
Other-than-temporary impairment of investments									0	14.8	17.0
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)
Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Impairment charge of assets no longer used									4.4	6.9
Impairment of Long-Lived Assets Held-for-use										4.9
Other-than-temporary impairment of investments											17.0
Gain (loss) on sale or impairment of long lived assets, net											(0.9)
Houlton [Member]
Schedule of Available-for-sale Securities [Line Items]
Asset Impairment Charges										$ 62.0