Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)		Jun. 30, 2022	Dec. 31, 2021
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		$ 1,036,000	$ 5,570,000
U.S. government and federal agency obligations		1,109,128,000	1,080,720,000
Government-sponsored enterprise obligations		47,108,000	51,755,000
State and municipal obligations		1,952,798,000	2,096,827,000
Agency mortgage-backed securities		4,923,683,000	5,683,000,000
Non-agency mortgage-backed securities		1,329,114,000	1,366,477,000
Asset-backed securities		3,794,487,000	3,539,219,000
Other debt securities		543,990,000	632,029,000
Trading debt securities		34,195,000	46,235,000
Equity securities		6,130,000	7,153,000
Private equity investments		161,771,000	147,406,000
Derivative Asset	[1]	12,404,000	41,842,000
Assets held in trust for deferred compensation plan		17,862,000	21,794,000
Total assets		13,933,706,000	14,720,027,000
Derivative Liabilities	[1]	27,599,000	12,101,000
Liabilities held in trust for deferred compensation plan		17,862,000	21,794,000
Total Liabilities		45,461,000	33,895,000
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		1,109,128,000	1,080,720,000
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		0	0
Equity securities		6,130,000	7,153,000
Private equity investments		0	0
Derivative Asset	[1]	0	0
Assets held in trust for deferred compensation plan		17,862,000	21,794,000
Total assets		1,133,120,000	1,109,667,000
Derivative Liabilities	[1]	0	0
Liabilities held in trust for deferred compensation plan		17,862,000	21,794,000
Total Liabilities		17,862,000	21,794,000
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		1,036,000	5,570,000
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		47,108,000	51,755,000
State and municipal obligations		1,950,982,000	2,094,843,000
Agency mortgage-backed securities		4,923,683,000	5,683,000,000
Non-agency mortgage-backed securities		1,329,114,000	1,366,477,000
Asset-backed securities		3,794,487,000	3,539,219,000
Other debt securities		543,990,000	632,029,000
Trading debt securities		34,195,000	46,235,000
Equity securities		0	0
Private equity investments		0	0
Derivative Asset	[1]	12,088,000	40,994,000
Assets held in trust for deferred compensation plan		0	0
Total assets		12,636,683,000	13,460,122,000
Derivative Liabilities	[1]	27,437,000	11,824,000
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		27,437,000	11,824,000
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		1,816,000	1,984,000
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		161,771,000	147,406,000
Derivative Asset	[1]	316,000	848,000
Assets held in trust for deferred compensation plan		0	0
Total assets		163,903,000	150,238,000
Derivative Liabilities	[1]	162,000	277,000
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		$ 162,000	$ 277,000

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