Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 15,684	$ 19,993
Derivative Assets	12,268	12,980
Derivative Liabilities	12,642	13,329
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	518,843	505,696
Government-sponsored enterprise obligations	758,229	741,766
State and municipal obligations	1,803,319	1,619,171
Agency mortgage-backed securities	2,795,929	2,772,338
Non-agency mortgage-backed securities	301,661	246,983
Other asset-backed securities	2,920,062	2,844,071
Other debt securities	138,652	141,757
Equity securities	45,945	43,898
Trading securities	15,684	19,993
Private equity investments	44,192	56,612
Derivative Assets	12,268	12,980
Assets held in trust	8,633	7,511
Total Assets	9,363,417	9,012,776
Derivative Liabilities	12,642	13,329
Total Liabilities	12,642	13,329
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	518,843	505,696
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	21,634	24,646
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust	8,633	7,511
Total Assets	549,110	537,853
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]
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	758,229	741,766
State and municipal obligations	1,671,211	1,491,447
Agency mortgage-backed securities	2,795,929	2,772,338
Non-agency mortgage-backed securities	301,661	246,983
Other asset-backed securities	2,920,062	2,844,071
Other debt securities	138,652	141,757
Equity securities	24,311	19,252
Trading securities	15,684	19,993
Private equity investments	0	0
Derivative Assets	12,264	12,976
Assets held in trust	0	0
Total Assets	8,638,003	8,290,583
Derivative Liabilities	12,450	13,260
Total Liabilities	12,450	13,260
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	0	0
State and municipal obligations	132,108	127,724
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	44,192	56,612
Derivative Assets	4	4
Assets held in trust	0	0
Total Assets	176,304	184,340
Derivative Liabilities	192	69
Total Liabilities	$ 192	$ 69