Loans and Leases and the Allowance for Credit Losses - Summary of Loan grades applied various classes of Commercial and Real Estate Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 99,299,080	$ 98,535,867
Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	16,236,649	16,963,561
Revolving Loans Converted to Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,327,284	1,387,378
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	27,811,190	27,574,564
Commercial, Financial, Leasing, etc. [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	26,062,280	25,927,474
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,453,841	1,340,263
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	295,069	306,827
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	11,506,323	12,063,060
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	10,864,179	11,352,416
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	536,752	584,751
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	105,392	125,893
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	41,002	42,974
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans Converted to Term Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	18,253	21,286
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans Converted to Term Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	14,299	13,970
Commercial, Financial, Leasing, etc. [Member] | Revolving Loans Converted to Term Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	8,450	7,718
Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	27,396,211	27,680,340
Commercial [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	22,244,935	23,282,787
Commercial [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	4,327,197	3,621,659
Commercial [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	824,079	775,894
Commercial [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	927,977	954,022
Commercial [Member] | Revolving Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	850,376	875,348
Commercial [Member] | Revolving Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	67,856	44,260
Commercial [Member] | Revolving Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	9,745	34,414
Residential Builder and Developer [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,278,991	1,249,738
Residential Builder and Developer [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,145,907	1,113,915
Residential Builder and Developer [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	131,860	134,729
Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,224	1,094
Residential Builder and Developer [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	257,109	240,993
Residential Builder and Developer [Member] | Revolving Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	253,319	236,943
Residential Builder and Developer [Member] | Revolving Loans [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,790	4,050
Other Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	8,750,772	8,707,811
Other Commercial Construction [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,444,459	7,644,349
Other Commercial Construction [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,180,088	949,423
Other Commercial Construction [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	126,225	114,039
Other Commercial Construction [Member] | Revolving Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	76,574	80,018
Other Commercial Construction [Member] | Revolving Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	71,183	74,611
Other Commercial Construction [Member] | Revolving Loans [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	5,391	5,407
Term Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	6,690,394	20,949,019	$ 18,077,950	$ 15,628,942	$ 15,326,970	$ 10,466,749	$ 9,890,946	$ 7,893,838	$ 7,438,037	$ 6,013,013
Term Loans [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,308,388	8,128,774	6,265,328	2,388,900	2,234,194	1,675,653	1,553,291	989,229	762,270	779,407
Term Loans [Member] | Commercial, Financial, Leasing, etc. [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	3,124,732	7,732,728	5,923,267	2,277,233	2,096,560	1,505,486	1,384,745	930,834	690,770	719,796
Term Loans [Member] | Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	182,972	388,326	335,409	84,358	107,197	113,940	109,828	41,587	54,978	39,930
Term Loans [Member] | Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	684	7,720	6,652	27,309	30,437	56,227	58,718	16,808	16,522	19,681
Term Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	632,185	3,906,363	3,695,943	5,203,887	5,265,817	3,925,746	3,957,643	3,018,239	2,919,419	3,511,628
Term Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	631,465	3,353,450	3,077,590	4,681,834	4,586,114	3,299,095	3,077,605	2,628,061	2,507,906	2,746,165
Term Loans [Member] | Commercial [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	720	526,037	584,844	400,154	556,339	579,507	833,519	290,885	269,903	568,144
Term Loans [Member] | Commercial [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount		26,876	33,509	121,899	123,364	47,144	46,519	99,293	141,610	197,319
Term Loans [Member] | Residential Builder and Developer [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	157,050	509,985	431,722	331,245	302,988	124,289	98,357	18,469	9,474	10,976
Term Loans [Member] | Residential Builder and Developer [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	157,050	506,295	429,172	223,880	194,524	109,453	83,260	15,048	8,844	10,976
Term Loans [Member] | Residential Builder and Developer [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount		3,690	2,550	106,847	107,946	14,836	15,097	3,421	630
Term Loans [Member] | Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount				518	518
Term Loans [Member] | Other Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	170,727	1,087,785	1,369,490	3,213,005	3,366,552	2,442,676	2,165,150	1,175,501	955,664	389,889
Term Loans [Member] | Other Commercial Construction [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	169,597	1,050,258	1,346,451	2,998,921	3,120,357	2,048,063	1,603,206	945,339	649,578	233,127
Term Loans [Member] | Other Commercial Construction [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,130	37,192	22,703	148,492	167,294	381,091	548,509	225,949	301,956	144,665
Term Loans [Member] | Other Commercial Construction [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount		335	$ 336	$ 65,592	$ 78,901	$ 13,522	$ 13,435	$ 4,213	$ 4,130	$ 12,097
Term Loans Prior Period [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	24,310,850	19,233,367
Term Loans Prior Period [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	2,140,394	1,506,567
Term Loans Prior Period [Member] | Commercial, Financial, Leasing, etc. [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,959,774	1,387,695
Term Loans Prior Period [Member] | Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	112,406	73,401
Term Loans Prior Period [Member] | Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	68,214	45,471
Term Loans Prior Period [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	9,997,227	7,160,455
Term Loans Prior Period [Member] | Commercial [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	7,513,879	5,698,834
Term Loans Prior Period [Member] | Commercial [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	2,014,016	1,212,672
Term Loans Prior Period [Member] | Commercial [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	469,332	248,949
Term Loans Prior Period [Member] | Residential Builder and Developer [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	22,291	13,781
Term Loans Prior Period [Member] | Residential Builder and Developer [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	19,738	11,320
Term Loans Prior Period [Member] | Residential Builder and Developer [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,847	1,885
Term Loans Prior Period [Member] | Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	706	576
Term Loans Prior Period [Member] | Other Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	646,615	318,937
Term Loans Prior Period [Member] | Other Commercial Construction [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	484,087	294,030
Term Loans Prior Period [Member] | Other Commercial Construction [Member] | Criticized Accrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	138,496	12,034
Term Loans Prior Period [Member] | Other Commercial Construction [Member] | Criticized Nonaccrual [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 24,032	$ 12,873