Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets [Abstract]
Cash and due from banks	$ 678,998	$ 798,757
Interest-bearing cash and cash equivalents	580,457	381,816
Trading securities	5,699,070	4,707,975
Investment securities, net of allowance	220,832	244,843
Available for sale securities	13,317,922	13,050,665
Fair value option securities	60,432	114,982
Restricted equity securities	134,885	171,391
Residential mortgage loans held for sale	200,842	252,316
Loans and Leases Receivable, Gross	21,416,449	23,007,520
Allowance for loan losses	(311,890)	(388,640)
Loans, net of allowance	21,104,559	22,618,880
Premises and equipment, net	556,400	551,308
Receivables	195,763	245,880
Goodwill	1,048,091	1,048,091
Intangible assets, net	105,694	113,436
Mortgage servicing rights	117,629	101,172
Real estate and other repossessed assets, net of allowance	57,337	90,526
Derivative contracts, net	1,701,443	810,688
Cash surrender value of bank-owned life insurance	401,163	398,758
Receivable on unsettled securities sales	70,954	62,386
Other assets	901,904	907,218
Total assets	47,154,375	46,671,088
Deposits [Abstract]
Noninterest-bearing demand deposits	13,380,409	12,266,338
Interest-bearing deposits: [Abstract]
Transaction	21,278,719	21,158,422
Savings	875,456	751,992
Time	1,905,349	1,967,128
Total deposits	37,439,933	36,143,880
Funds purchased and repurchase agreements	730,183	1,662,386
Other borrowings	1,546,231	1,882,970
Subordinated debentures	276,043	276,005
Accrued interest, taxes and expense	199,014	323,667
Derivative contracts, net	612,261	405,779
Due on unsettled securities purchases	576,536	257,627
Other liabilities	419,623	427,213
Total liabilities	41,799,824	41,379,527
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,373,101	1,368,062
Retained earnings	4,214,130	3,973,675
Treasury stock	(481,027)	(411,344)
Accumulated other comprehensive gain	226,768	335,868
Total shareholders’ equity	5,332,977	5,266,266
Non-controlling interests	21,574	25,295
Total equity	5,354,551	5,291,561
Total liabilities and equity	$ 47,154,375	$ 46,671,088