Commitments and Contingencies, Asset Retirement Obligations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015
Asset Retirement Obligations [Line Items]
Liabilities Settled	$ 29,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	9,687,000	[1],[2]	$ 9,090,000	[3]
Liabilities Incurred	0		0
Accretion	342,000		319,000
Cash Flow Revisions	1,392,000		278,000
Ending balance	11,392,000	[3],[4]	9,687,000	[1],[2]
Electric Plant Steam Production Asbestos
Asset Retirement Obligations [Line Items]
Liabilities Settled	0		0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	2,145,000	[1]	2,049,000
Liabilities Incurred	0		0
Accretion	49,000		45,000
Cash Flow Revisions	0		51,000
Ending balance	2,194,000	[4]	2,145,000	[1]
Electric Plant Steam Production Ash Containment
Asset Retirement Obligations [Line Items]
Liabilities Settled	0		0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	617,000	[1]	374,000
Liabilities Incurred	0		0
Accretion	18,000		14,000
Cash Flow Revisions	(183,000)		229,000
Ending balance	452,000	[4]	617,000	[1]
Electric Plant Electric Distribution
Asset Retirement Obligations [Line Items]
Liabilities Settled	0		0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	72,000	[1]	37,000
Liabilities Incurred	0		0
Accretion	3,000		1,000
Cash Flow Revisions	(43,000)		34,000
Ending balance	32,000	[4]	72,000	[1]
Electric Plant Other
Asset Retirement Obligations [Line Items]
Liabilities Settled	29,000		0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	391,000	[1]	412,000
Liabilities Incurred	0		0
Accretion	14,000		15,000
Cash Flow Revisions	0		(36,000)
Ending balance	376,000	[4]	391,000	[1]
Natural Gas Plant Gas Distribution
Asset Retirement Obligations [Line Items]
Liabilities Settled	0		0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	6,367,000	[1]	6,127,000
Liabilities Incurred	0		0
Accretion	256,000		240,000
Cash Flow Revisions	1,670,000		0
Ending balance	8,293,000	[4]	6,367,000	[1]
Common and Other Property Common Miscellaneous
Asset Retirement Obligations [Line Items]
Liabilities Settled	0		0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	95,000	[1]	91,000
Liabilities Incurred	0		0
Accretion	2,000		4,000
Cash Flow Revisions	(52,000)		0
Ending balance	$ 45,000	[4]	$ 95,000	[1]

[1] (a) There were no ARO liabilities recognized or settled during the year ended Dec. 31, 2015.

[2] (b) Included in other long-term liabilities balance in the consolidated balance sheet.

[3] (b) Included in other long-term liabilities balance in the consolidated balance sheet.

[4] (a) There were no ARO liabilities recognized during the year ended Dec. 31, 2016.