CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 34,091	$ 3,953
Securities AFS and transferred securities:
Change in unrealized holding (loss) gain on AFS securities during the period	(48,979)	61,486
Reclassification adjustment for amortization related to AFS and HTM debt securities	416	121
Reclassification adjustment for net gain on sale of AFS securities, included in net income	(2,003)	(5,541)
Derivatives:
Change in net unrealized gain (loss) on effective cash flow hedge interest rate swap derivatives	11,023	(19,600)
Reclassification adjustment of net loss (gain) related to derivatives designated as cash flow hedges	1,568	(101)
Pension plans:
Amortization of net actuarial loss and prior service credit, included in net periodic benefit cost	641	727
Other comprehensive (loss) income, before tax	(37,334)	37,092
Income tax benefit (expense) related to items of other comprehensive (loss) income	7,840	(7,789)
Other comprehensive (loss) income, net of tax	(29,494)	29,303
Comprehensive income	$ 4,597	$ 33,256