Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		Mar. 31, 2026	Dec. 31, 2025
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		$ 1,657	$ 4,028
U.S. government and federal agency obligations		3,147,293	3,279,100
Government-sponsored enterprise obligations		43,985	44,712
State and municipal obligations		654,824	664,733
Agency mortgage-backed securities		3,123,669	3,223,105
Non-agency mortgage-backed securities		414,777	435,688
Asset-backed securities		1,093,819	1,262,045
Other debt securities		167,760	186,130
Trading debt securities		44,329	40,080
Equity securities		46,193	47,551
Private equity investments		183,764	184,343
Derivative Asset	[1]	58,399	51,421
Assets held in trust for deferred compensation plan		22,437	23,276
Total assets		9,002,906	9,446,212
Derivative Liabilities	[1]	15,726	18,795
Liabilities held in trust for deferred compensation plan		22,437	23,276
Total Liabilities		38,163	42,071
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		3,147,293	3,279,100
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		13,233	13,215
Equity securities		46,193	47,551
Private equity investments		0	0
Derivative Asset	[1]	0	0
Assets held in trust for deferred compensation plan		22,437	23,276
Total assets		3,229,156	3,363,142
Derivative Liabilities	[1]	0	0
Liabilities held in trust for deferred compensation plan		22,437	23,276
Total Liabilities		22,437	23,276
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		1,657	4,028
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		43,985	44,712
State and municipal obligations		653,874	663,781
Agency mortgage-backed securities		3,123,669	3,223,105
Non-agency mortgage-backed securities		414,777	435,688
Asset-backed securities		1,093,819	1,262,045
Other debt securities		167,760	186,130
Trading debt securities		31,096	26,865
Equity securities		0	0
Private equity investments		0	0
Derivative Asset	[1]	58,216	51,232
Assets held in trust for deferred compensation plan		0	0
Total assets		5,588,853	5,897,586
Derivative Liabilities	[1]	15,666	18,718
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		15,666	18,718
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		950	952
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		183,764	184,343
Derivative Asset	[1]	183	189
Assets held in trust for deferred compensation plan		0	0
Total assets		184,897	185,484
Derivative Liabilities	[1]	60	77
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		$ 60	$ 77

[1] * The fair value of each class of derivative is shown in Note 12.