Consolidated Statement of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income
Loans and leases, including fees	$ 4,442,182	$ 4,164,561	$ 3,742,867
Investment securities
Fully taxable	288,532	323,912	361,157
Exempt from federal taxes	321	665	1,431
Deposits at banks	141,397	108,182	61,326
Other	7,161	1,391	1,014
Total interest income	4,879,593	4,598,711	4,167,795
Interest expense
Savings and interest-checking deposits	368,003	215,411	133,177
Time deposits	95,426	51,423	61,505
Deposits at Cayman Islands office	21,917	5,633	1,186
Short-term borrowings	24,741	5,386	1,511
Long-term borrowings	239,242	248,556	189,372
Total interest expense	749,329	526,409	386,751
Net interest income	4,130,264	4,072,302	3,781,044
Provision for credit losses	176,000	132,000	168,000
Net interest income after provision for credit losses	3,954,264	3,940,302	3,613,044
Other income
Brokerage services income	48,922	51,069	61,445
Trading account and foreign exchange gains	62,044	32,547	35,301
Gain (loss) on bank investment securities	18,037	(6,301)	21,279
Other revenues from operations	469,320	451,321	440,538
Total other income	2,061,679	1,856,000	1,851,143
Other expense
Salaries and employee benefits	1,900,797	1,752,264	1,648,794
Equipment and net occupancy	324,079	298,828	295,084
Outside data processing and software	229,731	199,025	184,670
FDIC assessments	41,535	68,526	101,871
Advertising and marketing	93,472	85,710	69,203
Printing, postage and supplies	39,893	35,658	35,960
Amortization of core deposit and other intangible assets	19,490	24,522	31,366
Other costs of operations	819,685	823,529	773,377
Total other expense	3,468,682	3,288,062	3,140,325
Income before taxes	2,547,261	2,508,240	2,323,862
Income taxes	618,112	590,160	915,556
Net income	1,929,149	1,918,080	1,408,306
Net income available to common shareholders
Basic	1,849,509	1,836,028	1,327,503
Diluted	$ 1,849,511	$ 1,836,035	$ 1,327,517
Net income per common share
Basic	$ 13.76	$ 12.75	$ 8.72
Diluted	$ 13.75	$ 12.74	$ 8.70
Mortgage Banking Revenues [Member]
Other income
Revenue from contract with customer	$ 457,770	$ 360,442	$ 363,827
Service Charges on Deposit Accounts [Member]
Other income
Revenue from contract with customer	432,978	429,337	427,372
Trust Income [Member]
Other income
Revenue from contract with customer	$ 572,608	$ 537,585	$ 501,381