Contingencies Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2008	Dec. 31, 1997 mi	Sep. 30, 2008	Dec. 31, 2003	Dec. 31, 1993
Loss Contingencies [Line Items]
investment in Trojan						87.00%
Customer refund for Trojan Investment, net of Interest				$ 15.4
Interest Rate Applied to Trojan Refund				9.60%
refund to customers for Trojan Investment including interest				33.1
Class action damages sought					260
Site Contingency, Names of Other Potentially Responsible Parties	100		69
river miles			5.7
Repayments of Pollution Control Bond		$ 5.8