SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT - Condensed Statements of Income (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed financial statements
Income tax benefit	$ 23,664	$ 30,423	$ 28,197
Net Income	$ 78,396	$ 94,347	$ 86,425
Weighted Average Number of Shares Outstanding (in shares)	36,955	36,921	36,880
Basic Earnings Per Common Share (in USD per share)	$ 2.12	$ 2.55	$ 2.34
Weighted Average Number of Diluted Common Shares Outstanding (in shares)	37,039	37,010	36,995
Fully Diluted Earnings per Common Share (in USD per share)	$ 2.11	$ 2.55	$ 2.33
Dividends Paid Per Common Share (in USD per share)	$ 1.525	$ 1.40	$ 1.28
Parent Company
Condensed financial statements
Operating revenues and other income	$ 0	$ 0	$ 0
Operating expenses and other expenses	2,093	542	90
Loss before equity in earnings of subsidiaries and income taxes	(2,093)	(542)	(90)
Equity in earnings of subsidiaries	79,892	94,808	86,307
Income before income taxes	77,799	94,266	86,217
Income tax benefit	(597)	(81)	(208)
Net Income	$ 78,396	$ 94,347	$ 86,425
Basic Earnings Per Common Share (in USD per share)	$ 2.12	$ 2.55	$ 2.34
Fully Diluted Earnings per Common Share (in USD per share)	$ 2.11	$ 2.55	$ 2.33