Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	$ 4,505,000	$ 4,981,000
U.S. government and federal agency obligations	715,310,000	727,076,000
Government-sponsored enterprise obligations	721,658,000	793,023,000
State and municipal obligations	1,812,791,000	1,741,957,000
Agency mortgage-backed securities	2,611,384,000	2,618,281,000
Non-agency mortgage-backed securities	863,158,000	879,963,000
Other asset-backed securities	2,440,055,000	2,644,381,000
Other debt securities	344,777,000	331,320,000
Equity securities	43,046,000	41,003,000
Trading securities	23,130,000	11,890,000
Private equity investments	67,432,000	63,032,000
Derivative Assets	27,568,000	12,771,000
Assets held in trust	9,449,000	9,278,000
Total Assets	9,684,263,000	9,878,956,000
Derivative Liabilities	27,195,000	12,729,000
Total Liabilities	27,195,000	12,729,000
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	715,310,000	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	21,217,000	20,263,000
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust	9,449,000	9,278,000
Total Assets	745,976,000	756,617,000
Derivative Liabilities	0	0
Total Liabilities	0	0
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	4,505,000	4,981,000
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	721,658,000	793,023,000
State and municipal obligations	1,795,582,000	1,724,762,000
Agency mortgage-backed securities	2,611,384,000	2,618,281,000
Non-agency mortgage-backed securities	863,158,000	879,963,000
Other asset-backed securities	2,440,055,000	2,644,381,000
Other debt securities	344,777,000	331,320,000
Equity securities	21,829,000	20,740,000
Trading securities	23,130,000	11,890,000
Private equity investments	0	0
Derivative Assets	26,796,000	12,507,000
Assets held in trust	0	0
Total Assets	8,852,874,000	9,041,848,000
Derivative Liabilities	26,929,000	12,534,000
Total Liabilities	26,929,000	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	17,209,000	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	67,432,000	63,032,000
Derivative Assets	772,000	264,000
Assets held in trust	0	0
Total Assets	85,413,000	80,491,000
Derivative Liabilities	266,000	195,000
Total Liabilities	$ 266,000	$ 195,000