STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 84,313	$ 90,223	$ 233,079	$ 242,818
Other comprehensive (loss) income, net of tax
Change in unrealized holding losses on available-for-sale securities	(17,178)	(3,732)	(69,082)	(9,808)
Amortization of prior service costs and net actuarial loss on pension and other postretirement plans	1,731	3,463	5,198	10,389
Total other comprehensive (loss) income, net of tax	(15,447)	(269)	(63,884)	581
Comprehensive income	$ 68,866	$ 89,954	$ 169,195	$ 243,399