CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income		$ 113,401	$ 82,153	$ 74,554
Securities AFS and transferred securities:
Change in unrealized holding (loss) gain on AFS securities during the period		(37,199)	105,845	87,481
Reclassification adjustment for amortization related to AFS and HTM debt securities		1,363	1,197	816
Reclassification adjustment for net gain on sale of AFS securities, included in net income		(3,862)	(8,257)	(756)
Derivatives:
Change in net unrealized gain (loss) on effective cash flow hedge interest rate swap derivatives		13,648	(23,462)	(9,118)
Reclassification adjustment of net loss (gain) related to derivatives designated as cash flow hedges		6,395	3,945	(2,043)
Retirement plans:
Amortization of net actuarial loss and prior service credit, included in net periodic benefit cost		1,264	3,028	2,378
Effect of settlement recognition		0	215	0
Prior service cost adjustment due to plan amendments	$ 163	0	163	0
Change in net actuarial gain (loss)		6,524	(593)	(9,816)
Other comprehensive (loss) income, before tax		(11,867)	82,081	68,942
Income tax benefit (expense) related to items of other comprehensive income (loss)		2,492	(17,237)	(14,478)
Other comprehensive (loss) income, net of tax		(9,375)	64,844	54,464
Comprehensive income		$ 104,026	$ 146,997	$ 129,018