Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,571,193	$ 1,586,696	$ 1,492,268	$ 1,741,311
Other comprehensive income (loss) before reclassification			21,394	(274,118)
Amounts reclassified from accumulated other comprehensive income (loss)			8,909	266
Other comprehensive income (loss), net of tax amount	(22,184)	(99,270)	(12,485)	(273,852)
Balance	1,570,351	1,508,945	1,570,351	1,508,945
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(254,442)	(17,774)
Other comprehensive income (loss) before reclassification			(2,967)	(259,475)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Other comprehensive income (loss), net of tax amount			(2,967)	(259,475)
Balance	(257,409)	(277,249)	(257,409)	(277,249)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(5,792)	(14,786)
Other comprehensive income (loss) before reclassification			0	0
Amounts reclassified from accumulated other comprehensive income (loss)			243	748
Other comprehensive income (loss), net of tax amount			243	748
Balance	(5,549)	(14,038)	(5,549)	(14,038)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(15,169)	0
Other comprehensive income (loss) before reclassification			(18,427)	14,643
Amounts reclassified from accumulated other comprehensive income (loss)			8,666	(482)
Other comprehensive income (loss), net of tax amount			(9,761)	(15,125)
Balance	(24,930)	(15,125)	(24,930)	(15,125)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(265,704)	(207,142)	(275,403)	(32,560)
Balance	$ (287,888)	$ (306,412)	$ (287,888)	$ (306,412)