Consolidated Statement of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest income
Loans and leases, including fees	$ 926,965	$ 980,372	$ 1,899,547	$ 2,027,193
Investment securities
Fully taxable	34,456	47,219	71,527	97,329
Exempt from federal taxes	10	29	65	104
Deposits at banks	8,710	4,179	15,584	23,145
Other	217	443	597	4,890
Total interest income	970,358	1,032,242	1,987,320	2,152,661
Interest expense
Savings and interest-checking deposits	8,052	26,454	19,556	104,456
Time deposits	5,084	19,883	12,094	41,755
Deposits at Cayman Islands office	16	161	201	3,580
Short-term borrowings	1	2	3	25
Long-term borrowings	14,865	28,605	31,731	68,903
Total interest expense	28,018	75,105	63,585	218,719
Net interest income	942,340	957,137	1,923,735	1,933,942
Provision for credit losses	(15,000)	325,000	(40,000)	575,000
Net interest income after provision for credit losses	957,340	632,137	1,963,735	1,358,942
Other income
Brokerage services income	10,265	10,463	23,378	23,592
Trading account and foreign exchange gains	6,502	8,290	12,786	29,306
Gain (loss) on bank investment securities	(10,655)	6,969	(22,937)	(13,813)
Other revenues from operations	112,699	87,190	223,629	220,366
Total other income	513,633	487,273	1,019,231	1,016,633
Other expense
Salaries and employee benefits	479,134	458,842	1,020,212	995,685
Equipment and net occupancy	80,848	77,089	163,319	156,729
Outside data processing and software	74,492	61,376	140,243	125,786
FDIC assessments	17,876	14,207	32,064	26,478
Advertising and marketing	13,364	9,842	27,992	32,217
Printing, postage and supplies	11,133	11,260	20,450	22,112
Amortization of core deposit and other intangible assets	2,737	3,913	5,475	7,826
Other costs of operations	185,761	170,513	375,034	346,625
Total other expense	865,345	807,042	1,784,789	1,713,458
Income before taxes	605,628	312,368	1,198,177	662,117
Income taxes	147,559	71,314	292,859	152,241
Net income	458,069	241,054	905,318	509,876
Net income available to common shareholders
Basic	438,756	223,098	866,848	473,794
Diluted	$ 438,759	$ 223,099	$ 866,852	$ 473,795
Net income per common share
Basic	$ 3.41	$ 1.74	$ 6.74	$ 3.67
Diluted	$ 3.41	$ 1.74	$ 6.73	$ 3.67
Average common shares outstanding
Basic	128,671	128,275	128,604	128,986
Diluted	128,842	128,333	128,756	129,044
Mortgage Banking Revenues [Member]
Other income
Revenue from contract with customer	$ 133,313	$ 145,024	$ 272,067	$ 272,933
Service Charges on Deposit Accounts [Member]
Other income
Revenue from contract with customer	98,518	77,455	191,295	183,616
Trust Income [Member]
Other income
Revenue from contract with customer	$ 162,991	$ 151,882	$ 319,013	$ 300,633