Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	$ 2,173,000	$ 0
U.S. government and federal agency obligations	420,399,000	501,407,000
Government-sponsored enterprise obligations	862,209,000	963,127,000
State and municipal obligations	1,847,159,000	1,813,201,000
Agency mortgage-backed securities	2,575,835,000	2,593,708,000
Non-agency mortgage-backed securities	817,197,000	382,744,000
Other asset-backed securities	2,584,688,000	3,091,993,000
Other debt securities	326,008,000	139,161,000
Equity securities	39,464,000	38,219,000
Trading securities	14,463,000	15,357,000
Private equity investments	66,875,000	57,581,000
Derivative Assets	16,369,000	10,457,000
Assets held in trust	8,825,000	8,848,000
Total Assets	9,581,664,000	9,615,803,000
Derivative Liabilities	16,251,000	10,948,000
Total Liabilities	16,251,000	10,948,000
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	420,399,000	501,407,000
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	19,509,000	17,975,000
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust	8,825,000	8,848,000
Total Assets	448,733,000	528,230,000
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	2,173,000	0
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	862,209,000	963,127,000
State and municipal obligations	1,753,970,000	1,718,058,000
Agency mortgage-backed securities	2,575,835,000	2,593,708,000
Non-agency mortgage-backed securities	817,197,000	382,744,000
Other asset-backed securities	2,584,688,000	3,091,993,000
Other debt securities	326,008,000	139,161,000
Equity securities	19,955,000	20,244,000
Trading securities	14,463,000	15,357,000
Private equity investments	0	0
Derivative Assets	15,916,000	10,454,000
Assets held in trust	0	0
Total Assets	8,972,414,000	8,934,846,000
Derivative Liabilities	16,017,000	10,722,000
Total Liabilities	16,017,000	10,722,000
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	93,189,000	95,143,000
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	66,875,000	57,581,000
Derivative Assets	453,000	3,000
Assets held in trust	0	0
Total Assets	160,517,000	152,727,000
Derivative Liabilities	234,000	226,000
Total Liabilities	$ 234,000	$ 226,000