Fair Values Of Assets And Liabilities (Summary Of Carrying Amounts And Estimated Fair Values Of Financial Instruments) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Interest bearing deposits with banks	$ 990,308	$ 865,575	$ 1,110,123
Available-for-sale securities	1,456,426	1,496,302	1,418,035
Trading account securities	509	4,879	38,261
Brokerage customer receivables	29,736	24,549	24,291
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	86,761	82,407	79,300
Mortgage loans held-for-sale, at lower of cost or market	5,881	14,785	15,278
Total loans, balance	10,333,746	9,934,239	9,599,726
FDIC indemnification asset	110,049	118,182	114,102
Accrued interest receivable and other	389,634	366,438	374,172
Notes payable	1,000	1,000	1,000
Federal Home Loan Bank advances	423,500	423,500	415,571
Subordinated notes	40,000	50,000	55,000
Other borrowings	395,724	217,289	218,424
Secured borrowings owed to securitization investors	600,000	600,000	600,000
Junior subordinated debentures	249,493	249,493	249,493
Carrying Value [Member]
Cash and cash equivalents	184,068	172,580
Interest bearing deposits with banks	990,308	865,575
Available-for-sale securities	1,456,426	1,496,302
Trading account securities	509	4,879
Brokerage customer receivables	29,736	24,549
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	86,761	82,407
Mortgage loans held-for-sale, at fair value	133,083	356,662
Mortgage loans held-for-sale, at lower of cost or market	5,881	14,785
Total loans, balance	10,333,746	9,934,239
Mortgage servicing rights	8,762	8,762
Nonqualified deferred compensations assets	4,564	3,613
Derivative assets	20,996	18,670
FDIC indemnification asset	110,049	118,182
Accrued interest receivable and other	138,435	137,744
Total financial assets	13,503,324	13,238,949
Non-maturity deposits	6,387,564	5,925,761
Deposits with stated maturities	4,871,696	4,877,912
Notes payable	1,000	1,000
Federal Home Loan Bank advances	423,500	423,500
Subordinated notes	40,000	50,000
Other borrowings	432,706	260,620
Secured borrowings owed to securitization investors	600,000	600,000
Junior subordinated debentures	249,493	249,493
Derivative liabilities	30,589	29,974
Accrued interest payable and other	13,555	15,518
Total financial liabilities	13,050,103	12,433,778
Fair Value [Member]
Cash and cash equivalents	184,068	172,580
Interest bearing deposits with banks	990,308	865,575
Available-for-sale securities	1,456,426	1,496,302
Trading account securities	509	4,879
Brokerage customer receivables	29,736	24,549
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	86,761	82,407
Mortgage loans held-for-sale, at fair value	133,083	356,662
Mortgage loans held-for-sale, at lower of cost or market	5,946	14,841
Total loans, balance	10,715,086	10,088,429
Mortgage servicing rights	8,762	8,762
Nonqualified deferred compensations assets	4,564	3,613
Derivative assets	20,996	18,670
FDIC indemnification asset	110,049	118,182
Accrued interest receivable and other	138,435	137,744
Total financial assets	13,884,729	13,393,195
Non-maturity deposits	6,387,564	5,925,761
Deposits with stated maturities	4,914,025	4,925,403
Notes payable	1,000	1,000
Federal Home Loan Bank advances	451,861	440,644
Subordinated notes	40,000	50,000
Other borrowings	432,706	260,620
Secured borrowings owed to securitization investors	605,792	600,333
Junior subordinated debentures	181,914	183,818
Derivative liabilities	30,589	29,974
Accrued interest payable and other	13,555	15,518
Total financial liabilities	$ 13,059,006	$ 12,433,071