Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)		Mar. 31, 2023	Dec. 31, 2022
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		$ 684,000	$ 0
U.S. government and federal agency obligations		1,020,223,000	1,035,406,000
Government-sponsored enterprise obligations		44,414,000	43,108,000
State and municipal obligations		1,453,814,000	1,767,109,000
Agency mortgage-backed securities		4,271,563,000	4,308,427,000
Non-agency mortgage-backed securities		1,207,969,000	1,211,607,000
Asset-backed securities		2,763,578,000	3,397,801,000
Other debt securities		467,055,000	474,858,000
Trading debt securities		41,584,000	43,523,000
Equity securities		6,083,000	6,210,000
Private equity investments		163,418,000	178,127,000
Derivative Asset	[1]	100,157,000	60,492,000
Assets held in trust for deferred compensation plan		18,656,000	17,856,000
Total assets		11,559,198,000	12,544,524,000
Derivative Liabilities	[1]	43,068,000	54,984,000
Liabilities held in trust for deferred compensation plan		18,656,000	17,856,000
Total Liabilities		61,724,000	72,840,000
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		1,020,223,000	1,035,406,000
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		500,000	0
Equity securities		6,083,000	6,210,000
Private equity investments		0	0
Derivative Asset	[1]	0	0
Assets held in trust for deferred compensation plan		18,656,000	17,856,000
Total assets		1,045,462,000	1,059,472,000
Derivative Liabilities	[1]	0	0
Liabilities held in trust for deferred compensation plan		18,656,000	17,856,000
Total Liabilities		18,656,000	17,856,000
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		684,000	0
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		44,414,000	43,108,000
State and municipal obligations		1,452,900,000	1,765,268,000
Agency mortgage-backed securities		4,271,563,000	4,308,427,000
Non-agency mortgage-backed securities		1,207,969,000	1,211,607,000
Asset-backed securities		2,763,578,000	3,397,801,000
Other debt securities		467,055,000	474,858,000
Trading debt securities		41,084,000	43,523,000
Equity securities		0	0
Private equity investments		0	0
Derivative Asset	[1]	100,036,000	60,458,000
Assets held in trust for deferred compensation plan		0	0
Total assets		10,349,283,000	11,305,050,000
Derivative Liabilities	[1]	42,920,000	54,865,000
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		42,920,000	54,865,000
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		914,000	1,841,000
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		163,418,000	178,127,000
Derivative Asset	[1]	121,000	34,000
Assets held in trust for deferred compensation plan		0	0
Total assets		164,453,000	180,002,000
Derivative Liabilities	[1]	148,000	119,000
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		$ 148,000	$ 119,000

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