Consolidated Statement of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income
Loans and leases, including fees	$ 1,060,832	$ 953,662	$ 3,065,272	$ 2,776,340
Investment securities
Fully taxable	80,118	87,937	244,989	276,057
Exempt from federal taxes	153	345	573	1,154
Deposits at banks	26,000	14,970	66,546	39,345
Other	272	296	1,050	760
Total interest income	1,167,375	1,057,210	3,378,430	3,093,656
Interest expense
Savings and interest-checking deposits	56,156	37,714	145,421	93,891
Time deposits	12,976	13,992	35,274	49,293
Deposits at Cayman Islands office	1,556	310	2,479	856
Short-term borrowings	1,600	554	3,866	1,148
Long-term borrowings	66,049	47,506	178,048	138,874
Total interest expense	138,337	100,076	365,088	284,062
Net interest income	1,029,038	957,134	3,013,342	2,809,594
Provision for credit losses	16,000	30,000	94,000	137,000
Net interest income after provision for credit losses	1,013,038	927,134	2,919,342	2,672,594
Other income
Brokerage services income	12,267	14,676	38,288	48,677
Trading account and foreign exchange gains	6,073	7,058	15,965	24,833
Loss on bank investment securities	(3,415)		(10,520)	(17)
Other revenues from operations	113,769	106,702	340,351	334,704
Total other income	459,294	459,429	1,375,404	1,367,090
Other expense
Salaries and employee benefits	431,371	398,605	1,313,336	1,246,400
Equipment and net occupancy	77,481	75,558	225,309	223,721
Outside data processing and software	50,678	45,761	148,819	134,637
FDIC assessments	18,849	23,969	58,689	78,149
Advertising and marketing	21,784	17,403	59,800	49,837
Printing, postage and supplies	8,843	8,732	26,881	27,397
Amortization of core deposit and other intangible assets	6,143	7,808	19,163	24,341
Other costs of operations	160,830	228,189	633,903	560,030
Total other expense	775,979	806,025	2,485,900	2,344,512
Income before taxes	696,353	580,538	1,808,846	1,695,172
Income taxes	170,262	224,615	436,985	609,269
Net income	526,091	355,923	1,371,861	1,085,903
Net income available to common shareholders
Basic	505,363	335,801	1,310,697	1,025,011
Diluted	$ 505,365	$ 335,804	$ 1,310,703	$ 1,025,023
Net income per common share
Basic	$ 3.54	$ 2.22	$ 9.01	$ 6.71
Diluted	3.53	2.21	9.00	6.69
Cash dividends per common share	$ 1.00	$ 0.75	$ 2.55	$ 2.25
Average common shares outstanding
Basic	142,822	151,347	145,424	152,866
Diluted	142,976	151,691	145,605	153,293
Mortgage Banking Revenues [Member]
Other income
Revenue from contract with customer	$ 88,408	$ 96,737	$ 268,213	$ 267,592
Service Charges on Deposit Accounts [Member]
Other income
Revenue from contract with customer	108,647	109,356	320,546	319,589
Trust Income [Member]
Other income
Revenue from contract with customer	$ 133,545	$ 124,900	$ 402,561	$ 371,712