Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,562,099	$ 1,631,382	$ 1,492,268	$ 1,741,311
Other comprehensive income (loss) before reclassification			4,333	(175,088)
Amounts reclassified from accumulated other comprehensive income (loss)			5,366	506
Other comprehensive income (loss), net of tax amount	(23,323)	(58,486)	9,699	(174,582)
Balance	1,571,193	1,586,696	1,571,193	1,586,696
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			14,256	(175,088)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Other comprehensive income (loss), net of tax amount			14,256	(175,088)
Balance	(240,186)	(192,862)	(240,186)	(192,862)
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)			170	506
Other comprehensive income (loss), net of tax amount			170	506
Balance	(5,622)	(14,280)	(5,622)	(14,280)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(15,169)	0
Other comprehensive income (loss) before reclassification			(9,923)	0
Amounts reclassified from accumulated other comprehensive income (loss)			5,196	0
Other comprehensive income (loss), net of tax amount			(4,727)	0
Balance	(19,896)	0	(19,896)	0
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(242,381)	(148,656)	(275,403)	(32,560)
Balance	$ (265,704)	$ (207,142)	$ (265,704)	$ (207,142)