Rate Matters (Details) - DSIC [Member] - PPUC [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Rate Matters [Abstract]
Distribution system improvement charge revenue	$ 899	$ 0	$ 0
Maximum [Member]
Rate Matters [Abstract]
Distribution system improvement charge percentage over base rate	5.00%
Minimum [Member]
Rate Matters [Abstract]
Distribution system improvement charge percentage over base rate	0.00%