Taxes Other Than Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	$ 59,955	$ 59,762	$ 56,628
Property [Member]
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	27,735	27,469	25,810
Gross Receipts, Excise And Franchise [Member]
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	13,500	14,521	13,458
Payroll [Member]
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	10,303	9,789	9,477
Regulatory Assessments [Member]
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	2,916	2,752	2,552
Pumping Fees [Member]
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	5,112	4,978	5,057
Other [Member]
Taxes Other Than Income Taxes [Line Items]
Total taxes other than income taxes	$ 389	$ 253	$ 274