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, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 15,740	$ 19,993
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	507,638	505,696
Government-sponsored enterprise obligations	796,773	741,766
State and municipal obligations	1,622,648	1,619,171
Agency mortgage-backed securities	2,892,499	2,772,338
Non-agency mortgage-backed securities	298,633	246,983
Other asset-backed securities	2,816,012	2,844,071
Other debt securities	136,853	141,757
Equity securities	44,060	43,898
Trading securities	15,740	19,993
Private equity investments	76,446	56,612
Derivative Assets	11,964	12,980
Assets held in trust	8,285	7,511
Total Assets	9,227,551	9,012,776
Derivative Liabilities	12,412	13,329
Total Liabilities	12,412	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	507,638	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	25,007	24,646
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust	8,285	7,511
Total Assets	540,930	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	796,773	741,766
State and municipal obligations	1,495,669	1,491,447
Agency mortgage-backed securities	2,892,499	2,772,338
Non-agency mortgage-backed securities	298,633	246,983
Other asset-backed securities	2,816,012	2,844,071
Other debt securities	136,853	141,757
Equity securities	19,053	19,252
Trading securities	15,740	19,993
Private equity investments	0	0
Derivative Assets	11,960	12,976
Assets held in trust	0	0
Total Assets	8,483,192	8,290,583
Derivative Liabilities	12,341	13,260
Total Liabilities	12,341	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	126,979	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	76,446	56,612
Derivative Assets	4	4
Assets held in trust	0	0
Total Assets	203,429	184,340
Derivative Liabilities	71	69
Total Liabilities	$ 71	$ 69