Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		Sep. 30, 2025	Dec. 31, 2024
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		$ 2,163	$ 2,981
U.S. government and federal agency obligations		2,925,238	2,555,252
Government-sponsored enterprise obligations		44,746	42,849
State and municipal obligations		695,698	742,891
Agency mortgage-backed securities		3,291,338	3,444,891
Non-agency mortgage-backed securities		452,424	568,689
Asset-backed securities		1,395,349	1,557,015
Other debt securities		193,793	225,266
Trading debt securities		56,282	38,034
Equity securities		43,365	48,359
Private equity investments		181,505	184,386
Derivative Asset	[1]	61,760	62,648
Assets held in trust for deferred compensation plan		22,789	21,849
Total assets		9,366,450	9,495,110
Derivative Liabilities	[1]	21,248	26,963
Liabilities held in trust for deferred compensation plan		22,789	21,849
Total Liabilities		44,037	48,812
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		2,925,238	2,555,252
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		13,082	10,219
Equity securities		43,365	48,359
Private equity investments		0	0
Derivative Asset	[1]	0	0
Assets held in trust for deferred compensation plan		22,789	21,849
Total assets		3,004,474	2,635,679
Derivative Liabilities	[1]	0	0
Liabilities held in trust for deferred compensation plan		22,789	21,849
Total Liabilities		22,789	21,849
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Residential mortgage loans held for sale		2,163	2,981
U.S. government and federal agency obligations		0	0
Government-sponsored enterprise obligations		44,746	42,849
State and municipal obligations		694,738	741,927
Agency mortgage-backed securities		3,291,338	3,444,891
Non-agency mortgage-backed securities		452,424	568,689
Asset-backed securities		1,395,349	1,557,015
Other debt securities		193,793	225,266
Trading debt securities		43,200	27,815
Equity securities		0	0
Private equity investments		0	0
Derivative Asset	[1]	61,566	62,555
Assets held in trust for deferred compensation plan		0	0
Total assets		6,179,317	6,673,988
Derivative Liabilities	[1]	21,143	26,905
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		21,143	26,905
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		960	964
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		181,505	184,386
Derivative Asset	[1]	194	93
Assets held in trust for deferred compensation plan		0	0
Total assets		182,659	185,443
Derivative Liabilities	[1]	105	58
Liabilities held in trust for deferred compensation plan		0	0
Total Liabilities		$ 105	$ 58

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