Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets [Abstract]
Cash and due from banks	$ 670,500	$ 735,836
Interest-bearing cash and cash equivalents	302,577	522,985
Trading securities	2,110,585	1,623,921
Investment securities, net of allowance	272,576	293,418
Available for sale securities	12,694,277	11,269,643
Fair value option securities	1,703,238	1,098,577
Restricted equity securities	390,042	460,552
Residential mortgage loans held for sale	204,720	182,271
Loans	22,463,970	21,750,987
Allowance for loan losses	(315,311)	(210,759)
Loans, net of allowance	22,148,659	21,540,228
Premises and equipment, net	546,093	535,519
Receivables	207,341	231,811
Goodwill	1,048,091	1,048,091
Intangible assets, net	121,807	125,271
Mortgage servicing rights	110,828	201,886
Real estate and other repossessed assets, net of allowance	36,744	20,359
Derivative contracts, net	922,716	323,375
Cash surrender value of bank-owned life insurance	391,006	389,879
Receivable on unsettled securities sales	2,171,881	1,020,404
Other assets	1,065,481	547,995
Total assets	47,119,162	42,172,021
Deposits [Abstract]
Noninterest-bearing demand deposits	9,821,582	9,461,291
Interest-bearing deposits: [Abstract]
Transaction	16,596,292	15,391,752
Savings	593,805	550,276
Time	2,232,473	2,217,849
Total deposits	29,244,152	27,621,168
Funds purchased and repurchase agreements	4,583,768	3,818,350
Other borrowings	5,529,554	4,527,055
Subordinated debentures	275,942	275,923
Accrued interest, taxes and expense	309,236	259,701
Derivative contracts, net	1,213,445	251,128
Due on unsettled securities purchases	537,709	182,547
Other liabilities	391,196	372,230
Total liabilities	42,085,002	37,308,102
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,354,826	1,350,995
Retained earnings	3,709,019	3,729,778
Treasury stock	(368,894)	(329,906)
Accumulated other comprehensive gain	331,292	104,923
Total shareholders’ equity	5,026,248	4,855,795
Non-controlling interests	7,912	8,124
Total equity	5,034,160	4,863,919
Total liabilities and equity	$ 47,119,162	$ 42,172,021