Accumulated Other Comprehensive Income (Loss) - Change in AOCI Components Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	$ 1,348,746	$ 1,448,885	$ 1,611,611	$ 1,583,531	$ 1,360,221	$ 1,374,507	$ 1,611,611	$ 1,374,507
Total Other Comprehensive Loss	(79,246)	(122,295)	(179,771)	(7,100)	319	(49,609)	(381,312)	(56,390)
Balance	1,282,384	1,348,746	1,448,885	1,597,109	1,583,531	1,360,221	1,282,384	1,597,109
Unrealized Gains and Losses on Net Investment Securities \| Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(335,758)		(32,940)	950		51,495	(32,940)	51,495
Other Comprehensive Income (Loss) Before Reclassifications	(81,832)			(7,544)			(384,650)	(55,406)
Unrealized Net Losses Related to the Transfer of Securities from Available-for-Sale to Held-to-Maturity	176,700						176,700
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0			(61)			0	(2,744)
Total Other Comprehensive Loss	94,868			(7,605)			(207,950)	(58,150)
Balance	(240,890)	(335,758)		(6,655)	950		(240,890)	(6,655)
Unrealized Gains and Losses on Net Investment Securities \| Held-to-maturity Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	101		54	(51)		(423)	54	(423)
Other Comprehensive Income (Loss) Before Reclassifications	0			0			0	0
Unrealized Net Losses Related to the Transfer of Securities from Available-for-Sale to Held-to-Maturity	(176,700)						(176,700)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	2,232			64			2,279	436
Total Other Comprehensive Loss	(174,468)			64			(174,421)	436
Balance	(174,367)	101		13	(51)		(174,367)	13
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(32,791)		(33,496)	(42,367)		(43,250)	(33,496)	(43,250)
Other Comprehensive Income (Loss) Before Reclassifications	0			0			0	0
Unrealized Net Losses Related to the Transfer of Securities from Available-for-Sale to Held-to-Maturity	0						0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	354			441			1,059	1,324
Total Other Comprehensive Loss	354			441			1,059	1,324
Balance	(32,437)	(32,791)		(41,926)	(42,367)		(32,437)	(41,926)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(368,448)	(246,153)	(66,382)	(41,468)	(41,787)	7,822	(66,382)	7,822
Other Comprehensive Income (Loss) Before Reclassifications	(81,832)			(7,544)			(384,650)	(55,406)
Unrealized Net Losses Related to the Transfer of Securities from Available-for-Sale to Held-to-Maturity	0						0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	2,586			444			3,338	(984)
Total Other Comprehensive Loss	(79,246)	(122,295)	(179,771)	(7,100)	319	(49,609)	(381,312)	(56,390)
Balance	$ (447,694)	$ (368,448)	$ (246,153)	$ (48,568)	$ (41,468)	$ (41,787)	$ (447,694)	$ (48,568)

Unrealized net losses from transfer of securities.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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