STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 298,569	$ 297,860	$ 293,304
Other comprehensive income, net of tax
Change in unrealized holding (losses) gains on available-for-sale securities	(58,692)	(17,112)	18,738
Pension and other postretirement plans	76,566	69,967	19,987
Total other comprehensive income, net of tax	17,874	52,855	38,725
Comprehensive income	$ 316,443	$ 350,715	$ 332,029