Fair Value Accounting (Carrying and Estimated Fair Values of Financial Instruments Carried on Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financial assets
Investment securities available for sale	$ 6,892,162	$ 3,991,632
Loans, net	36,152,813	25,696,018
Financial liabilities
Non-interest-bearing deposits	9,586,148	7,650,967
Total deposits	37,433,070	26,720,322
Federal funds purchased and securities sold under repurchase agreements	197,419	237,692
Other short-term borrowings	2,233,593	650,000
Long-term debt	2,153,600	1,657,157
Mortgage loans held for sale
Financial assets
Loans receivable held-for-sale	129,415	37,129
Level 1
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	1,182,470	1,143,564
Trading securities	0	1,128
Investment securities available for sale	19,782	122,077
Private equity investments	0	0
Mutual funds and mutual funds held in rabbi trusts	31,429	16,012
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	197,419	237,692
Other short-term borrowings	0	0
Long-term debt	0	0
Earnout liability	0	0
Derivative liabilities	0
Level 1 | Mortgage loans held for sale
Financial assets
Loans receivable held-for-sale	0	0
Level 1 | Other loans for sale
Financial assets
Loans receivable held-for-sale		0
Level 2
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	0	0
Trading securities	4,000	2,002
Investment securities available for sale	6,870,389	3,867,770
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	181,805	19,332
Financial liabilities
Non-interest-bearing deposits	9,586,148	7,650,967
Non-time interest-bearing deposits	18,313,513	14,065,959
Time deposits	9,578,012	4,989,570
Total deposits	37,477,673	26,706,496
Federal funds purchased and securities sold under repurchase agreements	0	0
Other short-term borrowings	2,233,593	650,000
Long-term debt	2,176,073	1,649,642
Earnout liability	0	0
Derivative liabilities	41,350	16,535
Level 2 | Mortgage loans held for sale
Financial assets
Loans receivable held-for-sale	129,415	37,129
Level 2 | Other loans for sale
Financial assets
Loans receivable held-for-sale		0
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	1,991	1,785
Private equity investments	11,289	11,028
Mutual funds and mutual funds held in rabbi trusts	0	0
Loans, net	36,154,866	25,438,890
GGL/SBA loans servicing asset	3,350	3,729
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
Other short-term borrowings	0	0
Long-term debt	0	0
Earnout liability	24,810	14,353
Derivative liabilities	3,335	1,673
Level 3 | Mortgage loans held for sale
Financial assets
Loans receivable held-for-sale	0	0
Level 3 | Other loans for sale
Financial assets
Loans receivable held-for-sale		1,506
Carrying Value
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	1,182,470	1,143,564
Trading securities	4,000	3,130
Investment securities available for sale	6,892,162	3,991,632
Private equity investments	11,289	11,028
Mutual funds and mutual funds held in rabbi trusts	31,429	16,012
Loans, net	36,152,813	25,696,018
GGL/SBA loans servicing asset	3,350	3,729
Derivative assets	181,805	19,332
Financial liabilities
Non-interest-bearing deposits	9,586,148	7,650,967
Non-time interest-bearing deposits	18,313,513	14,065,959
Time deposits	9,533,409	5,003,396
Total deposits	37,433,070	26,720,322
Federal funds purchased and securities sold under repurchase agreements	197,419	237,692
Other short-term borrowings	2,233,593	650,000
Long-term debt	2,153,600	1,657,157
Earnout liability	24,810	14,353
Derivative liabilities	44,685	18,208
Carrying Value | Mortgage loans held for sale
Financial assets
Loans receivable held-for-sale	129,415	37,129
Carrying Value | Other loans for sale
Financial assets
Loans receivable held-for-sale		1,506
Fair Value
Financial assets
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	1,182,470	1,143,564
Trading securities	4,000	3,130
Investment securities available for sale	6,892,162	3,991,632
Private equity investments	11,289	11,028
Mutual funds and mutual funds held in rabbi trusts	31,429	16,012
Loans, net	36,154,866	25,438,890
GGL/SBA loans servicing asset	3,350	3,729
Derivative assets	181,805	19,332
Financial liabilities
Non-interest-bearing deposits	9,586,148	7,650,967
Non-time interest-bearing deposits	18,313,513	14,065,959
Time deposits	9,578,012	4,989,570
Total deposits	37,477,673	26,706,496
Federal funds purchased and securities sold under repurchase agreements	197,419	237,692
Other short-term borrowings	2,233,593	650,000
Long-term debt	2,176,073	1,649,642
Earnout liability	24,810	14,353
Derivative liabilities	44,685	18,208
Fair Value | Mortgage loans held for sale
Financial assets
Loans receivable held-for-sale	$ 129,415	37,129
Fair Value | Other loans for sale
Financial assets
Loans receivable held-for-sale		$ 1,506