Unaudited 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	$ 28,505	$ 35,842	$ 66,800	$ 103,860
Other comprehensive income, net of tax:
Net change in fair value of securities available for sale	(4,321)	8,056	22,158	43,180
Net change in fair value of cash flow hedges	(6,144)	2,516	20,286	17,893
Net change in other comprehensive income for defined benefit postretirement plans	1,702	0	5,106	0
Total other comprehensive income	(8,763)	10,572	47,550	61,073
Total comprehensive income	$ 19,742	$ 46,414	$ 114,350	$ 164,933