Fair Value Accounting (Carrying and Estimated Fair Values of Financial Instruments Carried on Balance Sheet) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financial assets
Investment securities available for sale	$ 8,825,757	$ 7,962,438
Financial liabilities
Non-interest-bearing deposits	14,660,287	13,477,854
Total deposits	47,368,951	46,691,571
Securities sold under repurchase agreements	293,659	227,922
Long-term debt	1,202,825	1,202,494
Level 1
Financial assets
Total cash, cash equivalents, and restricted cash	3,328,266	4,252,917
Trading securities	0	0
Investment securities available for sale	66,456	20,257
Loans receivable held-for-sale	0	0
Private equity investments	0	0
Mutual funds and mutual funds held in rabbi trusts	39,943	37,650
Loans, net	0	0
GGL/SBA loans servicing asset	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
Securities sold under repurchase agreements	293,659	227,922
Trading liability for short positions		0
Long-term debt	0	0
Earnout liability	0	0
Derivative liabilities	0	0
Level 2
Financial assets
Total cash, cash equivalents, and restricted cash	0	0
Trading securities	4,386	10,880
Investment securities available for sale	8,759,301	7,940,160
Loans receivable held-for-sale		216,647
Private equity 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
Derivative assets	276,831	401,295
Financial liabilities
Non-interest-bearing deposits	14,660,287	13,477,854
Non-time interest-bearing deposits	27,492,165	27,265,521
Time deposits	5,240,983	5,970,146
Total deposits	47,393,435	46,713,521
Securities sold under repurchase agreements	0	0
Trading liability for short positions		7,717
Long-term debt	1,274,158	1,266,825
Earnout liability	0	0
Derivative liabilities	135,725	155,119
Level 3
Financial assets
Total cash, cash equivalents, and restricted cash	0	0
Trading securities	0	0
Investment securities available for sale	0	2,021
Loans receivable held-for-sale	751,892	544,292
Private equity investments	1,053	1,021
Mutual funds and mutual funds held in rabbi trusts	0	0
Loans, net	38,126,309	37,605,881
GGL/SBA loans servicing asset	3,305	3,258
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
Securities sold under repurchase agreements	0	0
Trading liability for short positions		0
Long-term debt	0	0
Earnout liability	5,677	5,677
Derivative liabilities	1,768	2,048
Carrying Value
Financial assets
Total cash, cash equivalents, and restricted cash	3,328,266	4,252,917
Trading securities	4,386	10,880
Investment securities available for sale	8,825,757	7,962,438
Loans receivable held-for-sale	993,887	760,123
Private equity investments	1,053	1,021
Mutual funds and mutual funds held in rabbi trusts	39,943	37,650
Loans, net	38,241,887	37,647,248
GGL/SBA loans servicing asset	3,305	3,258
Derivative assets	276,831	401,295
Financial liabilities
Non-interest-bearing deposits	14,660,287	13,477,854
Non-time interest-bearing deposits	27,492,165	27,265,521
Time deposits	5,216,499	5,948,196
Total deposits	47,368,951	46,691,571
Securities sold under repurchase agreements	293,659	227,922
Trading liability for short positions		7,717
Long-term debt	1,202,825	1,202,494
Earnout liability	5,677	5,677
Derivative liabilities	137,493	157,167
Fair Value
Financial assets
Total cash, cash equivalents, and restricted cash	3,328,266	4,252,917
Trading securities	4,386	10,880
Investment securities available for sale	8,825,757	7,962,438
Loans receivable held-for-sale	993,902	760,939
Private equity investments	1,053	1,021
Mutual funds and mutual funds held in rabbi trusts	39,943	37,650
Loans, net	38,126,309	37,605,881
GGL/SBA loans servicing asset	3,305	3,258
Derivative assets	276,831	401,295
Financial liabilities
Non-interest-bearing deposits	14,660,287	13,477,854
Non-time interest-bearing deposits	27,492,165	27,265,521
Time deposits	5,240,983	5,970,146
Total deposits	47,393,435	46,713,521
Securities sold under repurchase agreements	293,659	227,922
Trading liability for short positions		7,717
Long-term debt	1,274,158	1,266,825
Earnout liability	5,677	5,677
Derivative liabilities	$ 137,493	$ 157,167

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