Contingencies (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014 claims	Sep. 30, 2013 claims	Dec. 31, 1997	Dec. 31, 2013	Sep. 30, 2008	Sep. 30, 2000	Dec. 31, 1993
Loss Contingencies [Line Items]
investment in Trojan							87.00%
Regulatory asset related to Trojan						$ 5,000,000
Refund to customers for Trojan Investment including interest					33,100,000
Class action damages sought	260,000,000
contracts	119
Site Contingency, Names of Other Potentially Responsible Parties	100		69
Low estimate of range of cost of Portland Harbor cleanup in total	169,000,000
Upper estimated range of total cost of Portland harbor cleanup	1,800,000,000
Remediation cost estimate lower range	3,000,000			3,000,000
Remediation cost estimate upper range				8,000,000
Loss Contingency, Estimate of Possible Loss	3,000,000
regulatory asset for recovery of loss contingencies	3,000,000
Civil Penalty Claim - Per day per violation through January 12, 2009	32,500
Civil Penalty Claim - Per day per violation after January 12, 2009	37,500
Claims moved to dismiss	36
Loss Contingency, Pending Claims, Number	39
projects added to plaintiff's suit	12	2
projects encompassed by suit	40
Potential Income Tax Liability related to State Tax Court Ruling	$ 7,000,000