Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	$ 13,529	$ 15,327
U.S. government and federal agency obligations	907,652	917,147
Government-sponsored enterprise obligations	195,778	406,363
State and municipal obligations	1,328,039	1,611,366
Agency mortgage-backed securities	3,214,985	3,040,913
Non-agency mortgage-backed securities	1,047,716	905,793
Asset-backed securities	1,511,614	1,492,800
Other debt securities	332,257	351,060
Trading securities	27,059	18,269
Equity Securities, FV-NI	2,585	48,838
Private equity investments	85,659	55,752
Derivative Assets	41,210	8,349
Deferred Compensation Plan Assets	12,968	12,843
Total Assets	8,721,051	8,884,820
Derivative Liability	13,421	8,074
Deferred Compensation Liability, Current and Noncurrent	12,968	12,843
Total liabilities	26,389	20,917
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	0	0
U.S. government and federal agency obligations	907,652	917,147
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 securities	0	0
Equity Securities, FV-NI	2,585	19,864
Private equity investments	0	0
Derivative Assets	0	0
Deferred Compensation Plan Assets	12,968	12,843
Total Assets	923,205	949,854
Derivative Liability	0	0
Deferred Compensation Liability, Current and Noncurrent	12,968	12,843
Total liabilities	12,968	12,843
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	13,529	15,327
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	195,778	406,363
State and municipal obligations	1,313,881	1,594,350
Agency mortgage-backed securities	3,214,985	3,040,913
Non-agency mortgage-backed securities	1,047,716	905,793
Asset-backed securities	1,511,614	1,492,800
Other debt securities	332,257	351,060
Trading securities	27,059	18,269
Equity Securities, FV-NI	0	28,974
Private equity investments	0	0
Derivative Assets	40,627	7,723
Deferred Compensation Plan Assets	0	0
Total Assets	7,697,446	7,861,572
Derivative Liability	13,328	7,951
Deferred Compensation Liability, Current and Noncurrent	0	0
Total liabilities	13,328	7,951
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	0	0
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	0	0
State and municipal obligations	14,158	17,016
Agency mortgage-backed securities	0	0
Non-agency mortgage-backed securities	0	0
Asset-backed securities	0	0
Other debt securities	0	0
Trading securities	0	0
Equity Securities, FV-NI	0	0
Private equity investments	85,659	55,752
Derivative Assets	583	626
Deferred Compensation Plan Assets	0	0
Total Assets	100,400	73,394
Derivative Liability	93	123
Deferred Compensation Liability, Current and Noncurrent	0	0
Total liabilities	$ 93	$ 123