Investment Securities Schedule of Amortized Cost and Fair Values of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Amortized Cost	$ 3,008,323
Gross Unrealized Gains	18
Gross Unrealized Losses	(410,957)
Estimated Fair Value	2,597,384	$ 3,187,390
Amortized Cost, Held to Maturity	1,339,310	980,384
Gross Unrealized Gains, Held to Maturity	0	11,022
Gross Unrealized Losses, Held to Maturity	(197,600)	(25,539)
Debt Securities, Held-to-Maturity, Fair Value	1,141,710	965,867
US Government Debt Securities
Schedule of Investments [Line Items]
Amortized Cost	226,439	127,831
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(8,255)	(213)
Estimated Fair Value	218,184	127,618
US Government Agencies Debt Securities
Schedule of Investments [Line Items]
Amortized Cost	1,053
Gross Unrealized Gains	0
Gross Unrealized Losses	(47)
Estimated Fair Value	1,006
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,287,140	1,139,187
Gross Unrealized Gains	12	50,161
Gross Unrealized Losses	(248,967)	(678)
Estimated Fair Value	1,038,185	1,188,670
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	436,443	373,482
Gross Unrealized Gains	0	13,009
Gross Unrealized Losses	(36,828)	(358)
Estimated Fair Value	399,615	386,133
Collateralized Mortgage Obligations [Member]
Schedule of Investments [Line Items]
Amortized Cost	155,010	206,532
Gross Unrealized Gains	0	3,581
Gross Unrealized Losses	(12,609)	(754)
Estimated Fair Value	142,401	209,359
Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	246,854	231,607
Gross Unrealized Gains	6	1,224
Gross Unrealized Losses	(32,608)	(3,036)
Estimated Fair Value	214,252	229,795
Amortized Cost, Held to Maturity	470,879	404,958
Gross Unrealized Gains, Held to Maturity	0	11,022
Gross Unrealized Losses, Held to Maturity	(60,881)	(7,067)
Debt Securities, Held-to-Maturity, Fair Value	409,998	408,913
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	655,384	974,541
Gross Unrealized Gains	0	6,141
Gross Unrealized Losses	(71,643)	(9,534)
Estimated Fair Value	583,741	971,148
Amortized Cost, Held to Maturity	868,431	575,426
Gross Unrealized Gains, Held to Maturity	0	0
Gross Unrealized Losses, Held to Maturity	(136,719)	(18,472)
Debt Securities, Held-to-Maturity, Fair Value	$ 731,712	556,954
Auction Rate Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost		76,350
Gross Unrealized Gains		0
Gross Unrealized Losses		(1,683)
Estimated Fair Value		74,667
Debt Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost		3,129,530
Gross Unrealized Gains		74,116
Gross Unrealized Losses		(16,256)
Estimated Fair Value		$ 3,187,390

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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