Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets [Abstract]
Cash and due from banks	$ 761,130	$ 741,749
Interest-bearing cash and cash equivalents	465,458	401,675
Trading securities	1,675,212	1,956,923
Investment securities	304,224	355,187
Available for sale securities	11,024,551	8,857,120
Fair value option securities	1,816,398	283,235
Restricted equity securities	479,018	344,447
Residential mortgage loans held for sale	282,487	149,221
Loans	22,285,367	21,656,730
Allowance for loan losses	(204,432)	(207,457)
Loans, net of allowance	22,080,935	21,449,273
Premises and equipment, net	516,597	330,033
Receivables	219,420	204,960
Goodwill	1,048,091	1,049,263
Intangible assets, net	124,320	134,849
Mortgage servicing rights	193,661	259,254
Real estate and other repossessed assets, net of allowance	21,026	17,487
Derivative contracts, net	352,019	320,929
Cash surrender value of bank-owned life insurance	387,035	381,608
Receivable on unsettled securities sales	904,630	336,400
Other assets	470,993	446,891
Total assets	43,127,205	38,020,504
Deposits [Abstract]
Noninterest-bearing demand deposits	9,844,397	10,414,592
Interest-bearing deposits: [Abstract]
Transaction	13,521,545	12,206,576
Savings	557,593	529,215
Time	2,243,541	2,113,380
Total deposits	26,167,076	25,263,763
Funds purchased and repurchase agreements	3,413,051	1,018,411
Other borrowings	6,822,334	6,124,390
Subordinated debentures	275,909	275,913
Accrued interest, taxes and expense	218,775	192,826
Derivative contracts, net	336,791	362,306
Due on unsettled securities purchases	703,448	156,370
Other liabilities	352,156	183,480
Total liabilities	38,289,540	33,577,459
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,346,730	1,334,030
Retained earnings	3,655,590	3,369,654
Treasury stock	(307,062)	(198,995)
Accumulated other comprehensive gain (loss)	133,753	(72,585)
Total shareholders’ equity	4,829,016	4,432,109
Non-controlling interests	8,649	10,936
Total equity	4,837,665	4,443,045
Total liabilities and equity	$ 43,127,205	$ 38,020,504