Fair Value Of Assets And Liabilities (Summary Of Carrying Amounts And Estimated Fair Values Of Financial Instruments) (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Interest bearing deposits with banks	$ 900,755,000	$ 749,287,000	$ 946,193,000
Available-for-sale securities	1,869,344,000	1,291,797,000	1,710,321,000
Trading account securities	1,140,000	2,490,000	2,229,000
Brokerage customer receivables	31,085,000	27,925,000	25,361,000
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	88,216,000	100,434,000	85,144,000
Mortgage loans held-for-sale, at fair value	339,600,000		92,151,000
Mortgage loans held-for-sale, at lower of cost or market	10,728,000	13,686,000	2,335,000
Total loans	11,408,604,000	11,172,745,000	9,993,101,000
Nonqualified deferred compensation assets	5,315,000		3,845,000
FDIC indemnification asset	263,212,000	344,251,000	124,785,000
Accrued interest receivable and other	463,394,000	444,912,000	394,292,000
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Notes payable	52,639,000	52,822,000	1,000,000
Federal Home Loan Bank advances	466,391,000	474,481,000	423,500,000
Subordinated notes	35,000,000	35,000,000	50,000,000
Other borrowings	411,037,000	443,753,000	250,032,000
Total notes amount	428,000,000	600,000,000	600,000,000
Junior subordinated debentures	249,493,000	249,493,000	249,493,000
Carrying Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	160,602,000	169,704,000
Interest bearing deposits with banks	900,755,000	749,287,000
Available-for-sale securities	1,869,344,000	1,291,797,000
Trading account securities	1,140,000	2,490,000
Brokerage customer receivables	31,085,000	27,925,000
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	88,216,000	100,434,000
Mortgage loans held-for-sale, at fair value	339,600,000	306,838,000
Mortgage loans held-for-sale, at lower of cost or market	10,728,000	13,686,000
Total loans	11,408,604,000	11,172,745,000
Mortgage servicing rights	7,201,000	6,700,000
Nonqualified deferred compensation assets	5,315,000	4,299,000
Derivative assets	39,220,000	38,607,000
FDIC indemnification asset	263,212,000	344,251,000
Accrued interest receivable and other	153,755,000	147,207,000
Total financial assets	15,278,777,000	14,375,970,000
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Non-maturity deposits	7,841,467,000	7,424,367,000
Deposits with stated maturities	4,824,386,000	4,882,900,000
Notes payable	52,639,000	52,822,000
Federal Home Loan Bank advances	466,391,000	474,481,000
Subordinated notes	35,000,000	35,000,000
Other borrowings	411,037,000	443,753,000
Total notes amount	428,000,000	600,000,000
Junior subordinated debentures	249,493,000	249,493,000
Derivative liabilities	46,364,000	50,081,000
Accrued interest payable and other	11,531,000	12,952,000
Total financial liabilities	14,366,308,000	14,225,849,000
Fair Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	160,602,000	169,704,000
Interest bearing deposits with banks	900,755,000	749,287,000
Available-for-sale securities	1,869,344,000	1,291,797,000
Trading account securities	1,140,000	2,490,000
Brokerage customer receivables	31,085,000	27,925,000
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	88,216,000	100,434,000
Mortgage loans held-for-sale, at fair value	339,600,000	306,838,000
Mortgage loans held-for-sale, at lower of cost or market	10,905,000	13,897,000
Total loans	11,798,811,000	11,590,729,000
Mortgage servicing rights	7,201,000	6,700,000
Nonqualified deferred compensation assets	5,315,000	4,299,000
Derivative assets	39,220,000	38,607,000
FDIC indemnification asset	263,212,000	344,251,000
Accrued interest receivable and other	153,755,000	147,207,000
Total financial assets	15,669,161,000	14,794,165,000
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Non-maturity deposits	7,841,467,000	7,424,367,000
Deposits with stated maturities	4,859,697,000	4,917,740,000
Notes payable	52,639,000	52,822,000
Federal Home Loan Bank advances	498,504,000	507,368,000
Subordinated notes	35,000,000	35,000,000
Other borrowings	411,037,000	443,753,000
Total notes amount	430,044,000	603,294,000
Junior subordinated debentures	177,355,000	185,199,000
Derivative liabilities	46,364,000	50,081,000
Accrued interest payable and other	11,531,000	12,952,000
Total financial liabilities	$ 14,363,638,000	$ 14,232,576,000