Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		Mar. 31, 2024	Dec. 31, 2023
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		$ 1,185	$ 1,585
U.S. government and federal agency obligations		750,033	816,514
Government-sponsored enterprise obligations		43,845	43,962
State and municipal obligations		1,131,695	1,197,419
Agency mortgage-backed securities		3,754,837	3,901,346
Non-agency mortgage-backed securities		1,139,113	1,157,898
Asset-backed securities		1,877,805	2,107,485
Other debt securities		444,367	460,136
Trading debt securities		56,716	28,830
Equity securities		5,864	5,723
Private equity investments		183,706	176,667
Derivative Asset	[1]	94,758	116,876
Assets held in trust for deferred compensation plan		21,270	20,538
Total assets		9,505,194	10,034,979
Derivative Liabilities	[1]	38,546	37,899
Liabilities held in trust for deferred compensation plan		21,270	20,538
Total Liabilities		59,816	58,437
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		750,033	816,514
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		5,864	5,723
Private equity investments		0	0
Derivative Asset	[1]	0	0
Assets held in trust for deferred compensation plan		21,270	20,538
Total assets		777,167	842,775
Derivative Liabilities	[1]	0	0
Liabilities held in trust for deferred compensation plan		21,270	20,538
Total Liabilities		21,270	20,538
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		1,185	1,585
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		43,845	43,962
State and municipal obligations		1,130,739	1,196,472
Agency mortgage-backed securities		3,754,837	3,901,346
Non-agency mortgage-backed securities		1,139,113	1,157,898
Asset-backed securities		1,877,805	2,107,485
Other debt securities		444,367	460,136
Trading debt securities		56,716	28,830
Equity securities		0	0
Private equity investments		0	0
Derivative Asset	[1]	94,617	116,710
Assets held in trust for deferred compensation plan		0	0
Total assets		8,543,224	9,014,424
Derivative Liabilities	[1]	38,440	37,704
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		38,440	37,704
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		956	947
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		183,706	176,667
Derivative Asset	[1]	141	166
Assets held in trust for deferred compensation plan		0	0
Total assets		184,803	177,780
Derivative Liabilities	[1]	106	195
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		$ 106	$ 195

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