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, 2024	Dec. 31, 2023	Dec. 31, 2022
Condensed financial statements
Income before income taxes	$ 149,441	$ 166,520	$ 102,060
Income tax benefit	30,173	41,599	23,664
Net Income	$ 119,268	$ 124,921	$ 78,396
Weighted Average Number of Shares Outstanding (in shares)	37,464	36,976	36,955
Basic Earnings Per Common Share (usd per share)	$ 3.17	$ 3.37	$ 2.12
Weighted Average Number of Diluted Common Shares Outstanding (in shares)	37,583	37,077	37,039
Fully Diluted Earnings per Common Share (in USD per share)	$ 3.17	$ 3.36	$ 2.11
Dividends Paid Per Common Share (in USD per share)	$ 1.791	$ 1.655	$ 1.525
Parent Company
Condensed financial statements
Operating revenues and other income	$ 0	$ 0	$ 0
Operating expenses and other expenses	5,527	5,576	2,093
Loss before equity in earnings of subsidiaries and income taxes	(5,527)	(5,576)	(2,093)
Equity in earnings of subsidiaries	122,859	128,783	79,892
Income before income taxes	117,332	123,207	77,799
Income tax benefit	(1,936)	(1,714)	(597)
Net Income	$ 119,268	$ 124,921	$ 78,396
Weighted Average Number of Shares Outstanding (in shares)	37,464	36,976	36,955
Basic Earnings Per Common Share (usd per share)	$ 3.17	$ 3.37	$ 2.12
Weighted Average Number of Diluted Common Shares Outstanding (in shares)	37,583	37,077	37,039
Fully Diluted Earnings per Common Share (in USD per share)	$ 3.17	$ 3.36	$ 2.11
Dividends Paid Per Common Share (in USD per share)	$ 1.791	$ 1.655	$ 1.525