Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Taxes and Interest Paid:
Income taxes paid	$ 22,496	$ 21,084	$ 13,615
Interest paid	25,080	23,471	22,762
Non-Cash Transactions:
Accrued payables for investment in utility plant	23,736	27,403	20,131
Property installed by developers and conveyed	6,220	2,082	2,082
GSWC
Taxes and Interest Paid:
Income taxes paid	17,206	19,448	4,822
Interest paid	23,925	22,721	22,285
Non-Cash Transactions:
Accrued payables for investment in utility plant	23,736	27,403	20,128
Property installed by developers and conveyed	$ 6,220	$ 2,082	$ 2,082