Allowance for Credit Losses - Summary of Loan grades applied various classes of Commercial and Real Estate Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 98,535,867	$ 90,922,869
Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	16,963,561
Revolving Loans Converted to Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,387,378
Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	20,949,019	15,628,942	$ 10,466,749	$ 7,893,838	$ 6,013,013
Term Loans Prior Period [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	19,233,367
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	27,574,564	23,838,168
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	12,063,060
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans Converted to Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	42,974
Commercial, Financial, Leasing, etc. [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	25,927,474	22,595,821
Commercial, Financial, Leasing, etc. [Member] | Pass [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	11,352,416
Commercial, Financial, Leasing, etc. [Member] | Pass [Member] | Revolving Loans Converted to Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	21,286
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,340,263	895,790
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	584,751
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member] | Revolving Loans Converted to Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	13,970
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	306,827	346,557
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	125,893
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member] | Revolving Loans Converted to Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,718
Commercial, Financial, Leasing, etc. [Member] | Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	8,128,774	2,388,900	1,675,653	989,229	779,407
Commercial, Financial, Leasing, etc. [Member] | Term Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,732,728	2,277,233	1,505,486	930,834	719,796
Commercial, Financial, Leasing, etc. [Member] | Term Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	388,326	84,358	113,940	41,587	39,930
Commercial, Financial, Leasing, etc. [Member] | Term Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,720	27,309	56,227	16,808	19,681
Commercial, Financial, Leasing, etc. [Member] | Term Loans Prior Period [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,506,567
Commercial, Financial, Leasing, etc. [Member] | Term Loans Prior Period [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,387,695
Commercial, Financial, Leasing, etc. [Member] | Term Loans Prior Period [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	73,401
Commercial, Financial, Leasing, etc. [Member] | Term Loans Prior Period [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	45,471
Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	27,680,340	26,657,808
Commercial [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	954,022
Commercial [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	23,282,787	25,728,725
Commercial [Member] | Pass [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	875,348
Commercial [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,621,659	770,609
Commercial [Member] | Criticized Accrual [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	44,260
Commercial [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	775,894	158,474
Commercial [Member] | Criticized Nonaccrual [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	34,414
Commercial [Member] | Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,906,363	5,203,887	3,925,746	3,018,239	3,511,628
Commercial [Member] | Term Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,353,450	4,681,834	3,299,095	2,628,061	2,746,165
Commercial [Member] | Term Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	526,037	400,154	579,507	290,885	568,144
Commercial [Member] | Term Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	26,876	121,899	47,144	99,293	197,319
Commercial [Member] | Term Loans Prior Period [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,160,455
Commercial [Member] | Term Loans Prior Period [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	5,698,834
Commercial [Member] | Term Loans Prior Period [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,212,672
Commercial [Member] | Term Loans Prior Period [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	248,949
Residential Builder and Developer [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,249,738	1,547,245
Residential Builder and Developer [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	240,993
Residential Builder and Developer [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,113,915	1,419,162
Residential Builder and Developer [Member] | Pass [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	236,943
Residential Builder and Developer [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	134,729	124,101
Residential Builder and Developer [Member] | Criticized Accrual [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	4,050
Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,094	3,982
Residential Builder and Developer [Member] | Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	509,985	331,245	124,289	18,469	10,976
Residential Builder and Developer [Member] | Term Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	506,295	223,880	109,453	15,048	10,976
Residential Builder and Developer [Member] | Term Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,690	106,847	14,836	3,421
Residential Builder and Developer [Member] | Term Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount		518
Residential Builder and Developer [Member] | Term Loans Prior Period [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	13,781
Residential Builder and Developer [Member] | Term Loans Prior Period [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	11,320
Residential Builder and Developer [Member] | Term Loans Prior Period [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,885
Residential Builder and Developer [Member] | Term Loans Prior Period [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	576
Other Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	8,707,811	7,336,861
Other Commercial Construction [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	80,018
Other Commercial Construction [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,644,349	7,092,799
Other Commercial Construction [Member] | Pass [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	74,611
Other Commercial Construction [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	949,423	211,292
Other Commercial Construction [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	114,039	32,770
Other Commercial Construction [Member] | Criticized Nonaccrual [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	5,407
Other Commercial Construction [Member] | Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,087,785	3,213,005	2,442,676	1,175,501	389,889
Other Commercial Construction [Member] | Term Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,050,258	2,998,921	2,048,063	945,339	233,127
Other Commercial Construction [Member] | Term Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	37,192	148,492	381,091	225,949	144,665
Other Commercial Construction [Member] | Term Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	335	$ 65,592	$ 13,522	$ 4,213	$ 12,097
Other Commercial Construction [Member] | Term Loans Prior Period [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	318,937
Other Commercial Construction [Member] | Term Loans Prior Period [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	294,030
Other Commercial Construction [Member] | Term Loans Prior Period [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	12,034
Other Commercial Construction [Member] | Term Loans Prior Period [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 12,873