STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 80,147	$ 79,029	$ 148,766	$ 152,595
Other comprehensive (loss) income, net of tax
Change in unrealized holding (losses) gains on available-for-sale securities	(24,985)	2,676	(51,904)	(6,076)
Amortization of prior service costs and net actuarial loss on pension and other postretirement plans	1,737	3,463	3,467	6,926
Total other comprehensive (loss) income, net of tax	(23,248)	6,139	(48,437)	850
Comprehensive income	$ 56,899	$ 85,168	$ 100,329	$ 153,445