SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed financial statements
Net cash provided (used)	$ 67,683	$ 117,799	$ 115,584
Cash Flows From Investing Activities:
Net cash provided (used)	(188,764)	(167,102)	(145,092)
Cash Flows From Financing Activities:
Dividends paid	(61,195)	(56,356)	(51,689)
Net cash provided (used)	129,157	50,337	(2,266)
Net change in cash and cash equivalents	8,076	1,034	(31,774)
Cash and cash equivalents, beginning of period	5,997
Cash and cash equivalents, end of year	14,073	5,997
Parent Company
Condensed financial statements
Net cash provided (used)	67,041	56,398	36,799
Cash Flows From Investing Activities:
Loans (made to)/repaid from, wholly-owned subsidiaries	121,000	(81,000)	(46,000)
Increase in investment of subsidiary	(10,000)	0	0
Net cash provided (used)	111,000	(81,000)	(46,000)
Cash Flows From Financing Activities:
Net borrowings on notes payable to banks	(113,392)	81,000	60,500
Proceeds from note payable to GSWC	0	0	(26,000)
Repayment of note payable to GSWC	0	0	26,000
Dividends paid	(61,195)	(56,356)	(51,689)
Net cash provided (used)	(174,587)	24,644	8,811
Net change in cash and cash equivalents	3,454	42	(390)
Cash and cash equivalents, beginning of period	93	51	441
Cash and cash equivalents, end of year	$ 3,547	$ 93	$ 51