CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 41,477	$ 50,856	$ 107,498	$ 149,398
Other comprehensive (loss) income, net of tax
Unrealized gain (loss) on debt securities arising during the period	5,434	9,915	27,861	57,930
Change in retirement obligation	401	269	1,082	805
Unrealized gain (loss) on derivatives	0	73	0	217
Other comprehensive income (loss)	5,835	10,257	28,943	58,952
Comprehensive income	$ 47,312	$ 61,113	$ 136,441	$ 208,350