Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	$ 7,094,000	$ 4,981,000
U.S. government and federal agency obligations	720,919,000	727,076,000
Government-sponsored enterprise obligations	562,177,000	793,023,000
State and municipal obligations	1,833,861,000	1,741,957,000
Agency mortgage-backed securities	2,589,915,000	2,618,281,000
Non-agency mortgage-backed securities	831,616,000	879,963,000
Other asset-backed securities	2,298,725,000	2,644,381,000
Other debt securities	339,264,000	331,320,000
Equity securities	44,869,000	41,003,000
Trading securities	30,512,000	11,890,000
Private equity investments	62,813,000	63,032,000
Derivative Assets	35,255,000	12,771,000
Assets held in trust for deferred compensation plan	9,701,000	9,278,000
Total Assets	9,366,721,000	9,878,956,000
Derivative Liabilities	35,006,000	12,729,000
Liabilities held in trust for deferred compensation plan	9,701,000	9,278,000
Total Liabilities	44,707,000	22,007,000
Fair Value, Inputs, 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	720,919,000	727,076,000
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
Other asset-backed securities	0	0
Other debt securities	0	0
Equity securities	22,047,000	20,263,000
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust for deferred compensation plan	9,701,000	9,278,000
Total Assets	752,667,000	756,617,000
Derivative Liabilities	0	0
Liabilities held in trust for deferred compensation plan	9,701,000	9,278,000
Total Liabilities	9,701,000	9,278,000
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	7,094,000	4,981,000
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	562,177,000	793,023,000
State and municipal obligations	1,816,182,000	1,724,762,000
Agency mortgage-backed securities	2,589,915,000	2,618,281,000
Non-agency mortgage-backed securities	831,616,000	879,963,000
Other asset-backed securities	2,298,725,000	2,644,381,000
Other debt securities	339,264,000	331,320,000
Equity securities	22,822,000	20,740,000
Trading securities	30,512,000	11,890,000
Private equity investments	0	0
Derivative Assets	34,464,000	12,507,000
Assets held in trust for deferred compensation plan	0	0
Total Assets	8,532,771,000	9,041,848,000
Derivative Liabilities	34,717,000	12,534,000
Liabilities held in trust for deferred compensation plan	0	0
Total Liabilities	34,717,000	12,534,000
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	17,679,000	17,195,000
Agency mortgage-backed securities	0	0
Non-agency mortgage-backed securities	0	0
Other asset-backed securities	0	0
Other debt securities	0	0
Equity securities	0	0
Trading securities	0	0
Private equity investments	62,813,000	63,032,000
Derivative Assets	791,000	264,000
Assets held in trust for deferred compensation plan	0	0
Total Assets	81,283,000	80,491,000
Derivative Liabilities	289,000	195,000
Liabilities held in trust for deferred compensation plan	0	0
Total Liabilities	$ 289,000	$ 195,000