Commitments and Contingencies, Asset Retirement Obligations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	[1]	$ 9,090	[2]	$ 2,853
Liabilities recognized		0		515
Liabilities settled		0		0
Accretion		319		76
Cash Flow Revisions		278		5,646	[3]
Ending balance		9,687	[4],[5]	9,090	[1],[2]
Electric Plant Steam Production Asbestos
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		2,049	[2]	2,005
Liabilities recognized		0		0
Liabilities settled		0		0
Accretion		45		44
Cash Flow Revisions		51		0	[3]
Ending balance		2,145	[5]	2,049	[2]
Electric Plant Steam Production Ash Containment
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		374	[2]	361
Liabilities recognized		0		0
Liabilities settled		0		0
Accretion		14		13
Cash Flow Revisions		229		0	[3]
Ending balance		617	[5]	374	[2]
Electric Plant Electric Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		37	[2]	36
Liabilities recognized		0		0
Liabilities settled		0		0
Accretion		1		1
Cash Flow Revisions		34		0	[3]
Ending balance		72	[5]	37	[2]
Electric Plant Other
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		412	[2]	289
Liabilities recognized		0		113
Liabilities settled		0		0
Accretion		15		10
Cash Flow Revisions		(36)		0	[3]
Ending balance		391	[5]	412	[2]
Natural Gas Plant Gas Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		6,127	[2]	75
Liabilities recognized		0		402
Liabilities settled		0		0
Accretion		240		5
Cash Flow Revisions		0		5,645	[3]
Ending balance		6,367	[5]	6,127	[2]
Common and Other Property Common Miscellaneous
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		91	[2]	87
Liabilities recognized		0		0
Liabilities settled		0		0
Accretion		4		3
Cash Flow Revisions		0		1	[3]
Ending balance		$ 95	[5]	$ 91	[2]

[1] Included in other long-term liabilities balance in the consolidated balance sheet.

[2] There were no ARO liabilities settled during the year ended Dec. 31, 2014.

[3] In 2014, revisions were made to various AROs due to revised estimated cash flows and the timing of those cash flows. Changes in estimated excavation costs and the timing of future retirement activities resulted in revisions to AROs related to gas distribution.

[4] Included in other long-term liabilities balance in the consolidated balance sheet.

[5] There were no ARO liabilities recognized or settled during the year ended Dec. 31, 2015.