Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets [Abstract]
Cash and due from banks	$ 739,109	$ 741,749
Interest-bearing cash and cash equivalents	596,382	401,675
Trading securities	1,900,395	1,956,923
Investment securities	327,677	355,187
Available for sale securities	10,514,414	8,857,120
Fair value option securities	1,138,819	283,235
Restricted equity securities	461,017	344,447
Residential mortgage loans held for sale	193,570	149,221
Loans	22,255,652	21,656,730
Allowance for loan losses	(202,534)	(207,457)
Loans, net of allowance	22,053,118	21,449,273
Premises and equipment, net	468,368	330,033
Receivables	213,608	204,960
Goodwill	1,048,091	1,049,263
Intangible assets, net	124,473	134,849
Mortgage servicing rights	208,308	259,254
Real estate and other repossessed assets, net of allowance	16,940	17,487
Derivative contracts, net	415,221	320,929
Cash surrender value of bank-owned life insurance	384,193	381,608
Receivable on unsettled securities sales	583,421	336,400
Other assets	505,949	446,891
Total assets	41,893,073	38,020,504
Deposits [Abstract]
Noninterest-bearing demand deposits	9,667,557	10,414,592
Interest-bearing deposits: [Abstract]
Transaction	12,851,943	12,206,576
Savings	557,683	529,215
Time	2,227,938	2,113,380
Total deposits	25,305,121	25,263,763
Funds purchased and repurchase agreements	2,331,947	1,018,411
Other borrowings	7,823,809	6,124,390
Subordinated debentures	275,892	275,913
Accrued interest, taxes and expense	181,413	192,826
Derivative contracts, net	381,454	362,306
Due on unsettled securities purchases	565,268	156,370
Other liabilities	309,694	183,480
Total liabilities	37,174,598	33,577,459
Shareholders' equity: [Abstract]
Common stock	5	5
Capital surplus	1,343,082	1,334,030
Retained earnings	3,548,907	3,369,654
Treasury stock	(281,125)	(198,995)
Accumulated other comprehensive gain (loss)	98,569	(72,585)
Total shareholders’ equity	4,709,438	4,432,109
Non-controlling interests	9,037	10,936
Total equity	4,718,475	4,443,045
Total liabilities and equity	$ 41,893,073	$ 38,020,504