Summary of Significant Accounting Policies, Restricted Cash and Cash Equivalents (Details) (USD $)	1 Months Ended		9 Months Ended
	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Restricted Cash and Cash Equivalents Abstract]
Restricted cash and cash equivalents	$ 16,726,000		$ 16,726,000	$ 35,828,000
Diversified Lands Mitigation Escrow Agreement [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted cash and cash equivalents	97,000		97,000	97,000
Katrina/Rita Bond Payments [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted cash and cash equivalents	3,406,000		3,406,000	8,761,000
Collection net of operating expenses			14,700,000
Bond principal payments	6,400,000	6,700,000
Bond interest payments	3,400,000	3,600,000
Future Storm Restoration Costs [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted cash and cash equivalents	11,510,000		11,510,000	24,876,000
Increase (decrease) in restricted cash and cash equivalents			(13,400,000)
Future Storm Restoration Costs [Member] | Transfer to Restricted Investments [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted Cash and Cash Equivalents, Transfers			(4,500,000)
Future Storm Restoration Costs [Member] | Transfer to cover storm related expenses [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted Cash and Cash Equivalents, Transfers			(10,000,000)
Future Storm Restoration Costs [Member] | Increase in Storm Surcredits [Member]
Restricted Cash and Cash Equivalents Abstract]
Increase (decrease) in restricted cash and cash equivalents			1,100,000
Renewable Energy Grant [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted cash and cash equivalents	0		0	381,000
Nox Allowance Escrow [Member]
Restricted Cash and Cash Equivalents Abstract]
Restricted cash and cash equivalents	$ 1,713,000		$ 1,713,000	$ 1,713,000