Consolidated Statement of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Interest income
Loans and leases, including fees	$ 1,125,577	$ 1,024,471	$ 2,243,490	$ 2,004,440
Investment securities
Fully taxable	75,578	82,019	155,989	164,871
Exempt from federal taxes	77	172	172	420
Deposits at banks	36,325	21,869	63,732	40,546
Other	356	374	839	778
Total interest income	1,237,913	1,128,905	2,464,222	2,211,055
Interest expense
Savings and interest-checking deposits	91,557	48,738	167,695	89,265
Time deposits	24,931	11,362	46,012	22,298
Deposits at Cayman Islands office	6,039	542	10,777	923
Short-term borrowings	7,893	1,383	14,606	2,266
Long-term borrowings	66,012	58,093	133,591	111,999
Total interest expense	196,432	120,118	372,681	226,751
Net interest income	1,041,481	1,008,787	2,091,541	1,984,304
Provision for credit losses	55,000	35,000	77,000	78,000
Net interest income after provision for credit losses	986,481	973,787	2,014,541	1,906,304
Other income
Brokerage services income	12,478	12,629	24,954	26,021
Trading account and foreign exchange gains	18,453	5,255	29,255	9,892
Gain (loss) on bank investment securities	8,911	2,326	20,752	(7,105)
Other revenues from operations	112,763	100,280	247,200	226,582
Total other income	512,095	457,414	1,012,860	916,110
Other expense
Salaries and employee benefits	455,737	418,537	954,937	881,965
Equipment and net occupancy	79,150	73,031	158,497	147,828
Outside data processing and software	55,234	49,712	107,651	98,141
FDIC assessments	9,772	19,560	19,198	39,840
Advertising and marketing	24,046	21,768	44,321	38,016
Printing, postage and supplies	10,324	8,719	20,179	18,038
Amortization of core deposit and other intangible assets	5,077	6,388	10,097	13,020
Other costs of operations	233,692	178,862	452,500	473,073
Total other expense	873,032	776,577	1,767,380	1,709,921
Income before taxes	625,544	654,624	1,260,021	1,112,493
Income taxes	152,284	161,464	304,019	266,723
Net income	473,260	493,160	956,002	845,770
Net income available to common shareholders
Basic	452,632	472,598	914,718	805,338
Diluted	$ 452,633	$ 472,600	$ 914,719	$ 805,342
Net income per common share
Basic	$ 3.34	$ 3.26	$ 6.69	$ 5.49
Diluted	$ 3.34	$ 3.26	$ 6.69	$ 5.48
Average common shares outstanding
Basic	135,433	144,825	136,654	146,746
Diluted	135,464	144,998	136,685	146,941
Mortgage Banking Revenues [Member]
Other income
Revenue from contract with customer	$ 107,321	$ 92,499	$ 202,632	$ 179,805
Service Charges on Deposit Accounts [Member]
Other income
Revenue from contract with customer	107,787	106,784	210,899	211,899
Trust Income [Member]
Other income
Revenue from contract with customer	$ 144,382	$ 137,641	$ 277,168	$ 269,016