Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets [Abstract]
Cash and due from banks	$ 658,612	$ 735,836
Interest-bearing cash and cash equivalents	347,759	522,985
Trading securities	2,245,480	1,623,921
Investment securities, net of allowance	256,001	293,418
Investment Securities, fair value	284,929	314,402
Available for sale securities	12,817,269	11,269,643
Fair value option securities	134,756	1,098,577
Restricted equity securities	111,656	460,552
Residential mortgage loans held for sale	295,290	182,271
Loans	23,803,300	21,750,987
Allowance for loan losses	(419,777)	(210,759)
Loans, net of allowance	23,383,523	21,540,228
Premises and equipment, net	542,625	535,519
Receivables	245,514	231,811
Goodwill	1,048,091	1,048,091
Intangible assets, net	118,524	125,271
Mortgage servicing rights	97,644	201,886
Real estate and other repossessed assets, net of allowance	52,847	20,359
Allowance for real estate and other repossessed assets	(14,910)	(11,013)
Derivative contracts, net	593,568	323,375
Cash surrender value of bank-owned life insurance	396,497	389,879
Receivable on unsettled securities sales	1,934,495	1,020,404
Other assets	787,073	547,995
Total assets	46,067,224	42,172,021
Deposits [Abstract]
Noninterest-bearing demand deposits	12,047,338	9,461,291
Interest-bearing deposits: [Abstract]
Transaction	20,196,740	15,391,752
Savings	720,949	550,276
Time	2,007,973	2,217,849
Total deposits	34,973,000	27,621,168
Funds purchased and repurchase agreements	973,652	3,818,350
Other borrowings	2,771,429	4,527,055
Subordinated debentures	275,986	275,923
Accrued interest, taxes and expense	335,914	259,701
Derivative contracts, net	446,328	251,128
Due on unsettled securities purchases	641,817	182,547
Other liabilities	422,989	372,230
Total liabilities	40,841,115	37,308,102
Shareholders' equity: [Abstract]
Common stock	$ 5	$ 5
Common stock, par value (in dollars per share)	$ 0.00006	$ 0.00006
Common stock, shares authorized (in shares)	2,500,000,000	2,500,000,000
Common stock, shares issued (in shares)	(75,998,338)	(75,758,597)
Common stock, shares outstanding (in shares)	(75,998,338)	(75,758,597)
Capital surplus	$ 1,366,460	$ 1,350,995
Retained earnings	3,856,046	3,729,778
Treasury stock	$ (368,894)	$ (329,906)
Treasury stock, shares at cost (in shares)	5,692,505	5,178,999
Accumulated other comprehensive gain	$ 365,170	$ 104,923
Total shareholders’ equity	5,218,787	4,855,795
Non-controlling interests	7,322	8,124
Total equity	5,226,109	4,863,919
Total liabilities and equity	$ 46,067,224	$ 42,172,021