STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 86,241	$ 68,619
Other comprehensive income (loss), net of tax
Change in unrealized holding gains (losses) on available-for-sale securities	10,494	(26,919)
Amortization of prior service costs and net actuarial (gain) loss on pension and other postretirement plans	(2,742)	1,730
Total other comprehensive income (loss), net of tax	7,752	(25,189)
Comprehensive income	$ 93,993	$ 43,430