Rate and Regulatory Matters - Summary components of the requested rate increase (Details 1) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Public Utilities, Rate Matters [Abstract]
Approved Interim Revenue Increase (subject to refund), Amount	$ 3,818	$ 6,875
2016 Test Year Allocation
Public Utilities, Rate Matters [Abstract]
Total Requested Revenue Increase, Amount		19,296
Excluded from Interim Rates: Rate Base Effect of Prepaid Pension Asset, Amount		(2,480)
Approved Interim Revenue Increase (subject to refund), Amount		16,816
2016 Test Year Allocation | Increased Rate Base
Public Utilities, Rate Matters [Abstract]
Total Requested Revenue Increase, Amount		10,000
2016 Test Year Allocation | Increased Expenses
Public Utilities, Rate Matters [Abstract]
Total Requested Revenue Increase, Amount		7,700
2016 Test Year Allocation | Other
Public Utilities, Rate Matters [Abstract]
Total Requested Revenue Increase, Amount		$ 1,596