Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income, Before-tax Amount	$ 347,763	$ 209,445	$ 238,712
Net income, Tax (Expense) Benefit	(77,962)	(45,356)	(52,991)
Net income	269,801	164,089	185,721
Unrealized gains (losses) on available-for-sale securities:
Unrealized holding (losses) gains, Before-tax Amount	(92,231)	39,385	64,749
Unrealized holding (losses) gains, Tax (Expense) Benefit	23,294	(9,514)	(15,696)
Unrealized holding (losses) gains, Net of Tax Amount	(68,937)	29,871	49,053
Reclassification adjustment for (gains) losses recognized in net income, Before-tax Amount	(83)	(748)	1,021
Reclassification adjustment for (gains) losses recognized in net income, Tax (Expense) Benefit	(46)	191	(247)
Reclassification adjustment for (gains) losses recognized in net income, Net of Tax Amount	(129)	(557)	774
Net unrealized (losses) gains, Before-tax Amount	(92,314)	38,637	65,770
Net unrealized (losses) gains, Tax (Expense) Benefit	23,248	(9,323)	(15,943)
Net unrealized (losses) gains, Net of Tax Amount	(69,066)	29,314	49,827
Amortization of losses included in net income on available-for-sale securities transferred to held-to-maturity, Before-tax Amount	0	723	383
Amortization of losses included in net income on available-for-sale securities transferred to held-to-maturity, Tax (Expense) Benefit	0	(173)	(92)
Amortization of losses included in net income on available-for-sale securities transferred to held-to-maturity, Net of Tax Amount	0	550	291
Derivative instruments designated as cash flow hedges:
Amortization of losses included in net income on terminated derivative financial instruments previously accounted for as cash flow hedges, Before-tax Amount	0	0	337
Amortization of losses included in net income on terminated derivative financial instruments previously accounted for as cash flow hedges, Tax (Expense) Benefit	0	0	(86)
Amortization of losses included in net income on terminated derivative financial instruments previously accounted for as cash flow hedges, Net of Tax Amount	0	0	251
Unrealized holding gains (losses) on derivatives, Before-tax Amount	3,837	(149)	0
Unrealized holding gains (losses) on derivatives, Tax (Expense) Benefit	(979)	38	0
Unrealized holding gains (losses) on derivatives, Net of Tax Amount	2,858	(111)	0
Reclassification of losses on derivative instruments recognized in net income, Before-tax Amount	608	359	0
Reclassification of losses on derivative instruments recognized in net income, Tax (Expense) Benefit	(156)	(91)	0
Reclassification of losses on derivative instruments recognized in net income, Net of Tax Amount	452	268	0
Net cash flow hedge activity, Before-tax Amount	4,445	210	337
Net cash flow hedge activity, Tax (Expense) Benefit	(1,135)	(53)	(86)
Net cash flow hedge activity, Net of Tax Amount	3,310	157	251
Defined benefit pension plan activity:
Termination of defined benefit pension plan, Before-tax Amount	0	0	1,558
Termination of defined benefit pension plan, Tax (Expense) Benefit	0	0	(398)
Termination of defined benefit pension plan, Net of Tax Amount	0	0	1,160
Amendments to defined benefit pension plans, Before-tax Amount	0	0	(386)
Amendments to defined benefit pension plans,, Tax (Expense) Benefit	0	0	99
Amendments to defined benefit pension plans,, Net of Tax Amount	0	0	(287)
Net actuarial gain (loss) on defined benefit pension plans, Before-tax Amount	1,066	(1,804)	(2,390)
Net actuarial gain (loss) on defined benefit pension plans, Tax (Expense) Benefit	(273)	461	610
Net actuarial gain (loss) on defined benefit pension plans, Net of Tax Amount	793	(1,343)	(1,780)
Amortization of prior service cost and actuarial losses included in net periodic pension cost for defined benefit pension plans, Before-tax Amount	1,044	857	699
Amortization of prior service cost and actuarial losses included in net periodic pension cost for defined benefit pension plans, Tax (Expense) Benefit	(267)	(219)	(178)
Amortization of prior service cost and actuarial losses included in net periodic pension cost for defined benefit pension plans, Net of Tax Amount	777	638	521
Net defined benefit pension plan activity, Before-tax Amount	2,110	(947)	(519)
Net defined benefit pension plan activity, Tax (Expense) Benefit	(540)	242	133
Net defined benefit pension plan activity, Net of Tax Amount	1,570	(705)	(386)
Total other comprehensive (loss) income, Before-tax Amount	(85,759)	38,623	65,971
Total other comprehensive (loss) income, Tax (Expense) Benefit	21,573	(9,307)	(15,988)
Total other comprehensive (loss) income, Net of Tax Amount	(64,186)	29,316	49,983
Comprehensive income, Before-tax Amount	262,004	248,068	304,683
Comprehensive income, Tax (Expense) Benefit	(56,389)	(54,663)	(68,979)
Comprehensive income, Net of Tax Amount	$ 205,615	$ 193,405	$ 235,704