Fair Value Accounting (Carrying and Estimated Fair Values of Financial Instruments Carried on Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial assets
Trading securities		$ 7,212
Investment securities available for sale	$ 7,566,525	6,778,670
Private equity investments		19,389
GGL/SBA loans servicing asset		3,040
Derivative assets		140,016
Financial liabilities
Non-interest-bearing deposits	13,075,081	9,439,485
Total deposits	44,665,904	38,405,504
Federal funds purchased and securities sold under repurchase agreements	202,344	165,690
Other short-term borrowings	400,000	1,753,560
Long-term debt	1,628,385	2,153,897
Earnout liability		11,016
Derivative liabilities		37,071
Level 1
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	1,985,363	1,186,918
Trading securities	0	0
Investment securities available for sale	20,254	19,855
Loans receivable held-for-sale	0	0
Private equity investments	0	15,502
Mutual funds and mutual funds held in rabbi trusts	35,174	32,348
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
Federal funds purchased and securities sold under repurchase agreements	202,344	165,690
Trading liability for short positions		1,560
Other short-term borrowings	0	0
Long-term debt	0	0
Earnout liability	0	0
Derivative liabilities	0	0
Level 2
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	0	0
Trading securities	4,371	7,212
Investment securities available for sale	7,544,471	6,756,710
Loans receivable held-for-sale		115,173
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	463,028	140,016
Financial liabilities
Non-interest-bearing deposits	13,075,081	9,439,485
Non-time interest-bearing deposits	24,831,480	19,891,711
Time deposits	6,797,139	9,112,459
Total deposits	44,703,700	38,443,655
Federal funds purchased and securities sold under repurchase agreements	0	0
Trading liability for short positions		0
Other short-term borrowings	400,000	1,752,000
Long-term debt	1,687,448	2,185,717
Earnout liability	0	0
Derivative liabilities	178,508	34,732
Level 3
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	0	0
Trading securities	0	0
Investment securities available for sale	1,800	2,105
Loans receivable held-for-sale	458,716	0
Private equity investments	958	3,887
Mutual funds and mutual funds held in rabbi trusts	0	0
Loans, net	38,923,265	36,931,256
GGL/SBA loans servicing asset	3,100	3,040
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
Other short-term borrowings	0	0
Long-term debt	0	0
Earnout liability	15,924	11,016
Derivative liabilities	1,460	2,339
Carrying Value
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	1,985,363	1,186,918
Trading securities	4,371	7,212
Investment securities available for sale	7,566,525	6,778,670
Loans receivable held-for-sale	745,160	115,173
Private equity investments	958	19,389
Mutual funds and mutual funds held in rabbi trusts	35,174	32,348
Loans, net	38,946,047	36,881,048
GGL/SBA loans servicing asset	3,100	3,040
Derivative assets	463,028	140,016
Financial liabilities
Non-interest-bearing deposits	13,075,081	9,439,485
Non-time interest-bearing deposits	24,831,480	19,891,711
Time deposits	6,759,343	9,074,308
Total deposits	44,665,904	38,405,504
Federal funds purchased and securities sold under repurchase agreements	202,344	165,690
Trading liability for short positions		1,560
Other short-term borrowings	400,000	1,752,000
Long-term debt	1,628,385	2,153,897
Earnout liability	15,924	11,016
Derivative liabilities	179,968	37,071
Fair Value
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	1,985,363	1,186,918
Trading securities	4,371	7,212
Investment securities available for sale	7,566,525	6,778,670
Loans receivable held-for-sale	744,615	115,173
Private equity investments	958	19,389
Mutual funds and mutual funds held in rabbi trusts	35,174	32,348
Loans, net	38,923,265	36,931,256
GGL/SBA loans servicing asset	3,100	3,040
Derivative assets	463,028	140,016
Financial liabilities
Non-interest-bearing deposits	13,075,081	9,439,485
Non-time interest-bearing deposits	24,831,480	19,891,711
Time deposits	6,797,139	9,112,459
Total deposits	44,703,700	38,443,655
Federal funds purchased and securities sold under repurchase agreements	202,344	165,690
Trading liability for short positions		1,560
Other short-term borrowings	400,000	1,752,000
Long-term debt	1,687,448	2,185,717
Earnout liability	15,924	11,016
Derivative liabilities	$ 179,968	$ 37,071