Consolidated Statement of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income
Loans and leases, including fees	$ 3,742,867	$ 3,485,050	$ 2,778,151
Investment securities
Fully taxable	361,157	361,494	372,162
Exempt from federal taxes	1,431	2,606	4,263
Deposits at banks	61,326	45,516	15,252
Other	1,014	1,205	1,016
Total interest income	4,167,795	3,895,871	3,170,844
Interest expense
Savings and interest-checking deposits	133,177	87,704	46,140
Time deposits	61,505	102,841	27,059
Deposits at Cayman Islands office	1,186	797	615
Short-term borrowings	1,511	3,625	1,677
Long-term borrowings	189,372	231,017	252,766
Total interest expense	386,751	425,984	328,257
Net interest income	3,781,044	3,469,887	2,842,587
Provision for credit losses	168,000	190,000	170,000
Net interest income after provision for credit losses	3,613,044	3,279,887	2,672,587
Other income
Mortgage banking revenues	363,827	373,697	375,738
Service charges on deposit accounts	427,372	419,102	420,608
Trust income	501,381	472,184	470,640
Brokerage services income	61,445	63,423	64,770
Trading account and foreign exchange gains	35,301	41,126	30,577
Gain (loss) on bank investment securities	21,279	30,314	(130)
Other revenues from operations	440,538	426,150	462,834
Total other income	1,851,143	1,825,996	1,825,037
Other expense
Salaries and employee benefits	1,650,729	1,623,600	1,549,530
Equipment and net occupancy	295,084	295,141	272,539
Outside data processing and software	184,670	172,389	164,133
FDIC assessments	101,871	105,045	52,113
Advertising and marketing	69,203	87,137	59,227
Printing, postage and supplies	35,960	39,546	38,491
Amortization of core deposit and other intangible assets	31,366	42,613	26,424
Other costs of operations	771,442	682,014	660,475
Total other expense	3,140,325	3,047,485	2,822,932
Income before taxes	2,323,862	2,058,398	1,674,692
Income taxes	915,556	743,284	595,025
Net income	1,408,306	1,315,114	1,079,667
Net income available to common shareholders
Basic	1,327,503	1,223,459	987,689
Diluted	$ 1,327,517	$ 1,223,481	$ 987,724
Net income per common share
Basic	$ 8.72	$ 7.80	$ 7.22
Diluted	$ 8.70	$ 7.78	$ 7.18