Segment Reporting Assets by Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total Plant and Other Investments	$ 749,488	$ 708,385
Other Assets	202,381	190,398
Assets	951,869	898,783
Water Activities [Member]
Segment Reporting Information [Line Items]
Total Plant and Other Investments	748,374	707,362
Other Assets	199,955	188,590
Services and Rentals and Real Estate Combine [Member]
Segment Reporting Information [Line Items]
Total Plant and Other Investments	1,114	1,023
Other Assets	$ 2,426	$ 1,808