Fair Value Accounting (Carrying and Estimated Fair Values of Financial Instruments Carried on Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financial assets
Investment securities available for sale	$ 9,587,508	$ 10,918,329
Loans held for sale	696,450	750,642
Loans, net	42,150,099	38,884,361
Financial liabilities
Non-interest-bearing deposits	16,359,551	16,392,653
Total deposits	47,697,564	49,427,276
Federal funds purchased and securities sold under repurchase agreements	240,210	264,133
Long-term debt	4,434,327	1,204,229
Level 1
Financial assets
Total cash, cash equivalents, and restricted cash	1,867,804	3,009,853
Trading securities	0	0
Investment securities available for sale	467,756	117,838
Loans held for sale	0	0
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	40,151	43,657
Loans, net	0	0
GGL/SBA loans servicing asset	0	0
FRB and FHLB stock	0	0
Derivative assets	0	0
Financial liabilities
Non-interest-bearing deposits	0	0
Non-time interest-bearing deposits	0	0
Time deposits	0	0
Total deposits	0	0
Federal funds purchased and securities sold under repurchase agreements	240,210	264,133
Trading liability for short positions	16,236	0
Short-term FHLB advances	0
Long-term debt	0	0
Mutual funds held in rabbi trusts	25,486	27,205
Derivative liabilities	0	0
Level 2
Financial assets
Total cash, cash equivalents, and restricted cash	0	0
Trading securities	25,481	8,391
Investment securities available for sale	9,119,752	10,800,491
Loans held for sale	56,517	108,198
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
Loans, net	0	0
GGL/SBA loans servicing asset	0	0
FRB and FHLB stock	300,979	159,941
Derivative assets	82,087	191,708
Financial liabilities
Non-interest-bearing deposits	16,359,551	16,392,653
Non-time interest-bearing deposits	26,457,928	28,917,148
Time deposits	4,832,971	4,125,673
Total deposits	47,650,450	49,435,474
Federal funds purchased and securities sold under repurchase agreements	0	0
Trading liability for short positions	296	200
Short-term FHLB advances	599,700
Long-term debt	4,454,897	1,243,147
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	338,970	95,067
Level 3
Financial assets
Total cash, cash equivalents, and restricted cash	0	0
Trading securities	0	0
Investment securities available for sale	0	0
Loans held for sale	637,456	641,782
Other investments	11,212	12,185
Mutual funds and mutual funds held in rabbi trusts	0	0
Loans, net	40,952,610	39,118,275
GGL/SBA loans servicing asset	2,798	3,233
FRB and FHLB stock		0
Derivative assets	0	0
Financial liabilities
Non-interest-bearing deposits	0	0
Non-time interest-bearing deposits	0	0
Time deposits	0	0
Total deposits	0	0
Federal funds purchased and securities sold under repurchase agreements	0	0
Trading liability for short positions	0	0
Short-term FHLB advances	0
Long-term debt	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	1,184	3,535
Carrying Value
Financial assets
Total cash, cash equivalents, and restricted cash	1,867,804	3,009,853
Trading securities	25,481	8,391
Investment securities available for sale	9,587,508	10,918,329
Loans held for sale		750,642
Other investments	11,212	12,185
Mutual funds and mutual funds held in rabbi trusts	40,151	43,657
Loans, net	42,150,099	38,884,361
GGL/SBA loans servicing asset	2,798	3,233
FRB and FHLB stock	300,979	159,941
Derivative assets	82,087	191,708
Financial liabilities
Non-interest-bearing deposits	16,359,551	16,392,653
Non-time interest-bearing deposits	26,457,928	28,917,148
Time deposits	4,880,085	4,117,475
Total deposits	47,697,564	49,427,276
Federal funds purchased and securities sold under repurchase agreements	240,210	264,133
Trading liability for short positions	16,532	200
Short-term FHLB advances	599,700
Long-term debt	4,434,327	1,204,229
Mutual funds held in rabbi trusts	25,486	27,205
Derivative liabilities	340,154	98,602
Fair Value
Financial assets
Total cash, cash equivalents, and restricted cash	1,867,804	3,009,853
Trading securities	25,481	8,391
Investment securities available for sale	9,587,508	10,918,329
Loans held for sale	693,973	749,980
Other investments	11,212	12,185
Mutual funds and mutual funds held in rabbi trusts	40,151	43,657
Loans, net	40,952,610	39,118,275
GGL/SBA loans servicing asset	2,798	3,233
FRB and FHLB stock	300,979	159,941
Derivative assets	82,087	191,708
Financial liabilities
Non-interest-bearing deposits	16,359,551	16,392,653
Non-time interest-bearing deposits	26,457,928	28,917,148
Time deposits	4,832,971	4,125,673
Total deposits	47,650,450	49,435,474
Federal funds purchased and securities sold under repurchase agreements	240,210	264,133
Trading liability for short positions	16,532	200
Short-term FHLB advances	599,700
Long-term debt	4,454,897	1,243,147
Mutual funds held in rabbi trusts	25,486	27,205
Derivative liabilities	$ 340,154	$ 98,602