STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 131,040	$ 84,313	$ 335,133	$ 233,079
Other comprehensive loss, net of tax
Change in unrealized holding (losses) gains on available-for-sale securities	(5,902)	(17,178)	2,846	(69,082)
Amortization of prior service costs and net actuarial (gain) loss on pension and other postretirement plans	(2,742)	1,731	(8,226)	5,198
Total other comprehensive loss, net of tax	(8,644)	(15,447)	(5,380)	(63,884)
Comprehensive income	$ 122,396	$ 68,866	$ 329,753	$ 169,195