Consolidated Statement of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest income
Loans and leases, including fees	$ 4,164,561	$ 3,742,867	$ 3,485,050
Investment securities
Fully taxable	323,912	361,157	361,494
Exempt from federal taxes	665	1,431	2,606
Deposits at banks	108,182	61,326	45,516
Other	1,391	1,014	1,205
Total interest income	4,598,711	4,167,795	3,895,871
Interest expense
Savings and interest-checking deposits	215,411	133,177	87,704
Time deposits	51,423	61,505	102,841
Deposits at Cayman Islands office	5,633	1,186	797
Short-term borrowings	5,386	1,511	3,625
Long-term borrowings	248,556	189,372	231,017
Total interest expense	526,409	386,751	425,984
Net interest income	4,072,302	3,781,044	3,469,887
Provision for credit losses	132,000	168,000	190,000
Net interest income after provision for credit losses	3,940,302	3,613,044	3,279,887
Other income
Brokerage services income	51,069	61,445	63,423
Trading account and foreign exchange gains	32,547	35,301	41,126
Gain (loss) on bank investment securities	(6,301)	21,279	30,314
Other revenues from operations	451,321	440,538	426,150
Total other income	1,856,000	1,851,143	1,825,996
Other expense
Salaries and employee benefits	1,752,264	1,648,794	1,618,074
Equipment and net occupancy	298,828	295,084	295,141
Outside data processing and software	199,025	184,670	172,389
FDIC assessments	68,526	101,871	105,045
Advertising and marketing	85,710	69,203	87,137
Printing, postage and supplies	35,658	35,960	39,546
Amortization of core deposit and other intangible assets	24,522	31,366	42,613
Other costs of operations	823,529	773,377	687,540
Total other expense	3,288,062	3,140,325	3,047,485
Income before taxes	2,508,240	2,323,862	2,058,398
Income taxes	590,160	915,556	743,284
Net income	1,918,080	1,408,306	1,315,114
Net income available to common shareholders
Basic	1,836,028	1,327,503	1,223,459
Diluted	$ 1,836,035	$ 1,327,517	$ 1,223,481
Net income per common share
Basic	$ 12.75	$ 8.72	$ 7.80
Diluted	$ 12.74	$ 8.70	$ 7.78
Mortgage Banking Revenues [Member]
Other income
Revenue from contract with customer	$ 360,442	$ 363,827	$ 373,697
Service Charges on Deposit Accounts [Member]
Other income
Revenue from contract with customer	429,337	427,372	419,102
Trust Income [Member]
Other income
Revenue from contract with customer	$ 537,585	$ 501,381	$ 472,184