Fair Value Accounting (Carrying And Estimated Fair Values Of Financial Instruments Carried On Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets
Interest bearing funds with Federal Reserve Bank	$ 1,297,581	$ 527,090
Interest earning deposits with banks	6,047	18,720
Federal funds sold and securities purchased under resale agreements	48,820	58,060
Trading account assets	12,329	9,314
Mortgage loans held for sale	54,072	51,545
Other loans held for sale	31,253	0
Investment securities available for sale	3,825,443	3,718,195
Loans, net	24,237,677	23,604,633
Financial liabilities
Non-interest bearing deposits	7,302,682	7,085,804
Federal funds purchased, other short-term borrowings and other short-term liabilities	141,539	159,699
Long-term debt	1,882,607	2,160,881
Level 1
Financial assets
Cash and cash equivalents	386,459	395,175
Interest bearing funds with Federal Reserve Bank	1,297,581	527,090
Interest earning deposits with banks	6,047	18,720
Federal funds sold and securities purchased under resale agreements	48,820	58,060
Trading account assets	0	1,890
Mortgage loans held for sale	0	0
Other loans held for sale	0
Investment securities available for sale	86,343	114,676
Private equity investments	0	0
Mutual funds held in Rabbi Trusts	13,439	11,479
Loans, net	0	0
GGL/SBA loans servicing asset	0
Derivative assets	0	0
Financial liabilities
Non-interest bearing deposits	0	0
Interest bearing deposits	0	0
Federal funds purchased, other short-term borrowings and other short-term liabilities	141,539	159,699
Long-term debt	0	0
Other liabilities	0	0
Derivative liability positions	0	0
Level 2
Financial assets
Cash and cash equivalents	0	0
Interest bearing funds with Federal Reserve Bank	0	0
Interest earning deposits with banks	0	0
Federal funds sold and securities purchased under resale agreements	0	0
Trading account assets	12,329	7,424
Mortgage loans held for sale	54,072	51,545
Other loans held for sale	0
Investment securities available for sale	3,737,182	3,601,723
Private equity investments	0	0
Mutual funds held in Rabbi Trusts	0	0
Loans, net	0	0
GGL/SBA loans servicing asset	0
Derivative assets	15,870	20,623
Financial liabilities
Trading account liabilities	7,860
Non-interest bearing deposits	7,302,682	7,085,804
Interest bearing deposits	18,891,446	17,560,021
Federal funds purchased, other short-term borrowings and other short-term liabilities	0	0
Long-term debt	1,929,043	2,217,544
Other liabilities	0	0
Derivative liability positions	12,401	17,531
Level 3
Financial assets
Cash and cash equivalents	0	0
Interest bearing funds with Federal Reserve Bank	0	0
Interest earning deposits with banks	0	0
Federal funds sold and securities purchased under resale agreements	0	0
Trading account assets	0	0
Mortgage loans held for sale	0	0
Other loans held for sale	31,253
Investment securities available for sale	1,918	1,796
Private equity investments	15,671	25,493
Mutual funds held in Rabbi Trusts	0	0
Loans, net	24,193,343	23,709,434
GGL/SBA loans servicing asset	4,270
Derivative assets	0	0
Financial liabilities
Non-interest bearing deposits	0	0
Interest bearing deposits	0	0
Federal funds purchased, other short-term borrowings and other short-term liabilities	0	0
Long-term debt	0	0
Other liabilities	16,000	14,000
Derivative liability positions	4,693	5,768
Carrying Value
Financial assets
Cash and cash equivalents	386,459	395,175
Interest bearing funds with Federal Reserve Bank	1,297,581	527,090
Interest earning deposits with banks	6,047	18,720
Federal funds sold and securities purchased under resale agreements	48,820	58,060
Trading account assets	12,329	9,314
Mortgage loans held for sale	54,072	51,545
Other loans held for sale	31,253
Investment securities available for sale	3,825,443	3,718,195
Private equity investments	15,671	25,493
Mutual funds held in Rabbi Trusts	13,439	11,479
Loans, net	24,487,360	23,856,391
GGL/SBA loans servicing asset	4,270
Derivative assets	15,870	20,623
Financial liabilities
Trading account liabilities	7,860
Non-interest bearing deposits	7,302,682	7,085,804
Interest bearing deposits	18,883,546	17,562,256
Federal funds purchased, other short-term borrowings and other short-term liabilities	141,539	159,699
Long-term debt	1,882,607	2,160,881
Other liabilities	16,000	14,000
Derivative liability positions	17,094	23,299
Fair Value
Financial assets
Cash and cash equivalents	386,459	395,175
Interest bearing funds with Federal Reserve Bank	1,297,581	527,090
Interest earning deposits with banks	6,047	18,720
Federal funds sold and securities purchased under resale agreements	48,820	58,060
Trading account assets	12,329	9,314
Mortgage loans held for sale	54,072	51,545
Other loans held for sale	31,253
Investment securities available for sale	3,825,443	3,718,195
Private equity investments	15,671	25,493
Mutual funds held in Rabbi Trusts	13,439	11,479
Loans, net	24,193,343	23,709,434
GGL/SBA loans servicing asset	4,270
Derivative assets	15,870	20,623
Financial liabilities
Trading account liabilities	7,860
Non-interest bearing deposits	7,302,682	7,085,804
Interest bearing deposits	18,891,446	17,560,021
Federal funds purchased, other short-term borrowings and other short-term liabilities	141,539	159,699
Long-term debt	1,929,043	2,217,544
Other liabilities	16,000	14,000
Derivative liability positions	$ 17,094	$ 23,299