Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,492,268	$ 1,741,311	$ 1,741,117
Other comprehensive income (loss) before reclassification	43,185	(244,088)	(32,971)
Amounts reclassified from accumulated other comprehensive income (loss)	(12,495)	(1,245)	(1,462)
Other comprehensive income (loss), net of tax amount	55,680	(242,843)	(31,509)
Balance	1,661,847	1,492,268	1,741,311
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(254,442)	(17,774)	17,331
Other comprehensive income (loss) before reclassification	49,801	(236,668)	(35,105)
Amounts reclassified from accumulated other comprehensive income (loss)	(29)	0	0
Other comprehensive income (loss), net of tax amount	49,772	(236,668)	(35,105)
Balance	(204,670)	(254,442)	(17,774)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(5,792)	(14,786)	(18,382)
Other comprehensive income (loss) before reclassification	(518)	8,094	2,134
Amounts reclassified from accumulated other comprehensive income (loss)	235	900	1,462
Other comprehensive income (loss), net of tax amount	(283)	8,994	3,596
Balance	(6,075)	(5,792)	(14,786)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(15,169)	0	0
Other comprehensive income (loss) before reclassification	(6,098)	(15,514)	0
Amounts reclassified from accumulated other comprehensive income (loss)	(12,289)	345	0
Other comprehensive income (loss), net of tax amount	6,191	(15,169)	0
Balance	(8,978)	(15,169)	0
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(275,403)	(32,560)	(1,051)
Balance	$ (219,723)	$ (275,403)	$ (32,560)