Accounts Receivable (Net Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable [Abstract]
Billed utility revenue	$ 69,205	$ 68,347
Other	5,285	4,392
Gross accounts receivable	74,490	72,739
Less allowance for doubtful accounts	7,353	6,914	$ 7,071	$ 7,095
Accounts receivable after allowance for doubtful accounts	$ 67,137	$ 65,825