Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Dec. 31, 2022
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		$ 366	$ 0
U.S. government and federal agency obligations		947,976	1,035,406
Government-sponsored enterprise obligations		40,593	43,108
State and municipal obligations		1,178,414	1,767,109
Agency mortgage-backed securities		3,792,567	4,308,427
Non-agency mortgage-backed securities		1,137,448	1,211,607
Asset-backed securities		2,313,545	3,397,801
Other debt securities		450,285	474,858
Trading debt securities		35,564	43,523
Equity securities		5,453	6,210
Private equity investments		165,322	178,127
Derivative Asset	[1]	112,182	60,492
Assets held in trust for deferred compensation plan		18,859	17,856
Total assets		10,198,574	12,544,524
Derivative Liabilities	[1]	58,718	54,984
Liabilities held in trust for deferred compensation plan		18,859	17,856
Total Liabilities		77,577	72,840
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		0	0
U.S. government and federal agency obligations		947,976	1,035,406
Government-sponsored enterprise obligations		0	0
State and municipal obligations		0	0
Agency mortgage-backed securities		0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Other debt securities		0	0
Trading debt securities		0	0
Equity securities		5,453	6,210
Private equity investments		0	0
Derivative Asset	[1]	0	0
Assets held in trust for deferred compensation plan		18,859	17,856
Total assets		972,288	1,059,472
Derivative Liabilities	[1]	0	0
Liabilities held in trust for deferred compensation plan		18,859	17,856
Total Liabilities		18,859	17,856
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		366	0
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		40,593	43,108
State and municipal obligations		1,177,476	1,765,268
Agency mortgage-backed securities		3,792,567	4,308,427
Non-agency mortgage-backed securities		1,137,448	1,211,607
Asset-backed securities		2,313,545	3,397,801
Other debt securities		450,285	474,858
Trading debt securities		35,564	43,523
Equity securities		0	0
Private equity investments		0	0
Derivative Asset	[1]	112,136	60,458
Assets held in trust for deferred compensation plan		0	0
Total assets		9,059,980	11,305,050
Derivative Liabilities	[1]	58,674	54,865
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		58,674	54,865
Significant Unobservable Inputs (Level 3)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		0	0
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		0	0
State and municipal obligations		938	1,841
Agency mortgage-backed securities		0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Other debt securities		0	0
Trading debt securities		0	0
Equity securities		0	0
Private equity investments		165,322	178,127
Derivative Asset	[1]	46	34
Assets held in trust for deferred compensation plan		0	0
Total assets		166,306	180,002
Derivative Liabilities	[1]	44	119
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		$ 44	$ 119

[1] * The fair value of each class of derivative is shown in Note 11.