Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 15,501	$ 15,357
Derivative Assets	13,230	10,457
Derivative Liabilities	13,782	10,948
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	2,770	0
U.S. government and federal agency obligations	436,392	501,407
Government-sponsored enterprise obligations	1,068,767	963,127
State and municipal obligations	1,811,545	1,813,201
Agency mortgage-backed securities	2,709,914	2,593,708
Non-agency mortgage-backed securities	490,233	382,744
Other asset-backed securities	3,162,824	3,091,993
Other debt securities	198,018	139,161
Equity securities	39,549	38,219
Trading securities	15,501	15,357
Private equity investments	61,162	57,581
Derivative Assets	13,230	10,457
Assets held in trust	9,392	8,848
Total Assets	10,019,297	9,615,803
Derivative Liabilities	13,782	10,948
Total Liabilities	13,782	10,948
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	436,392	501,407
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	19,604	17,975
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust	9,392	8,848
Total Assets	465,388	528,230
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	2,770	0
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	1,068,767	963,127
State and municipal obligations	1,718,274	1,718,058
Agency mortgage-backed securities	2,709,914	2,593,708
Non-agency mortgage-backed securities	490,233	382,744
Other asset-backed securities	3,162,824	3,091,993
Other debt securities	198,018	139,161
Equity securities	19,945	20,244
Trading securities	15,501	15,357
Private equity investments	0	0
Derivative Assets	12,819	10,454
Assets held in trust	0	0
Total Assets	9,399,065	8,934,846
Derivative Liabilities	13,529	10,722
Total Liabilities	13,529	10,722
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	93,271	95,143
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	61,162	57,581
Derivative Assets	411	3
Assets held in trust	0	0
Total Assets	154,844	152,727
Derivative Liabilities	253	226
Total Liabilities	$ 253	$ 226