Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,586,696	$ 1,779,309	$ 1,741,311	$ 1,741,117
Other comprehensive income (loss) before reclassification			(274,118)	(19,236)
Amounts reclassified from accumulated other comprehensive income (loss)			266	1,207
Other comprehensive income (loss), net of tax amount	(99,270)	(8,439)	(273,852)	(18,029)
Balance	1,508,945	1,768,947	1,508,945	1,768,947
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(17,774)	17,331
Other comprehensive income (loss) before reclassification			(259,475)	(19,236)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Other comprehensive income (loss), net of tax amount			(259,475)	(19,236)
Balance	(277,249)	(1,905)	(277,249)	(1,905)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(14,786)	(18,382)
Other comprehensive income (loss) before reclassification			0	0
Amounts reclassified from accumulated other comprehensive income (loss)			748	1,207
Other comprehensive income (loss), net of tax amount			748	1,207
Balance	(14,038)	(17,175)	(14,038)	(17,175)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(207,142)	(10,641)	(32,560)	(1,051)
Balance	(306,412)	(19,080)	(306,412)	(19,080)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			0	0
Other comprehensive income (loss) before reclassification			(14,643)	0
Amounts reclassified from accumulated other comprehensive income (loss)			(482)	0
Other comprehensive income (loss), net of tax amount			(15,125)	0
Balance	$ (15,125)	$ 0	$ (15,125)	$ 0