Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets [Abstract]
Cash and due from banks	$ 767,805	$ 712,067
Interest-bearing cash and cash equivalents	599,976	2,125,343
Trading securities	4,891,096	9,136,813
Investment securities, net of allowance	183,824	210,444
Available for sale securities	12,894,534	13,157,817
Fair value option securities	185,003	43,770
Restricted equity securities	77,389	83,113
Residential mortgage loans held for sale	169,474	192,295
Loans and Leases Receivable, Gross	20,674,429	20,205,680
Allowance for loan losses	(246,473)	(256,421)
Loans, net of allowance	20,427,956	19,949,259
Premises and equipment, net	574,786	574,148
Receivables	238,694	223,021
Goodwill	1,044,749	1,044,749
Intangible assets, net	87,761	91,778
Mortgage servicing rights	209,563	163,198
Real estate and other repossessed assets, net of allowance	24,492	24,589
Derivative contracts, net	2,680,207	1,097,297
Cash surrender value of bank-owned life insurance	407,763	405,607
Receivable on unsettled securities sales	229,404	56,172
Other assets	1,132,031	957,951
Total assets	46,826,507	50,249,431
Deposits [Abstract]
Noninterest-bearing demand deposits	15,242,341	15,344,423
Interest-bearing deposits: [Abstract]
Transaction	21,689,829	23,268,573
Savings	979,365	924,735
Time	1,514,416	1,704,328
Total deposits	39,425,951	41,242,059
Funds purchased and repurchase agreements	1,068,329	2,326,449
Other borrowings	36,246	36,753
Subordinated debentures	131,209	131,226
Accrued interest, taxes and expense	238,048	273,041
Derivative contracts, net	557,834	275,625
Due on unsettled securities purchases	81,016	160,686
Other liabilities	434,350	435,221
Total liabilities	41,972,983	44,881,060
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,381,666	1,378,794
Retained earnings	4,473,884	4,447,691
Treasury stock	(588,147)	(535,129)
Accumulated other comprehensive gain (loss)	(417,826)	72,371
Total shareholders’ equity	4,849,582	5,363,732
Non-controlling interests	3,942	4,639
Total equity	4,853,524	5,368,371
Total liabilities and equity	$ 46,826,507	$ 50,249,431