Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 47,663	$ 8,445
Other comprehensive income, net of tax:
Net change in fair value of securities available for sale	(74,904)	26,192
Net change in fair value of cash flow hedges	(5,948)	29,075
Net change in other comprehensive income for defined benefit postretirement plans	426	0
Total other comprehensive (loss) income	(80,426)	55,267
Total comprehensive (loss) income	$ (32,763)	$ 63,712