Loans and Leases - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Modification	Dec. 31, 2019 USD ($) Modification	Dec. 31, 2018 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	5,250	412	557
Pre-modification Recorded Investment	$ 862,507	$ 143,556	$ 175,583
Loans and leases, net of unearned discount	$ 806,046	$ 127,024	$ 180,224
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			83
Pre-modification Recorded Investment			$ 30,217
Loans and leases, net of unearned discount			$ 30,731
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	394	150	203
Pre-modification Recorded Investment	$ 246,479	$ 63,715	$ 102,445
Loans and leases, net of unearned discount	$ 199,918	$ 63,356	$ 102,914
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	161	51
Pre-modification Recorded Investment	$ 310,578	$ 48,315
Loans and leases, net of unearned discount	$ 295,231	$ 31,345
Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	2	3	1
Pre-modification Recorded Investment	$ 13,602	$ 1,559	$ 752
Loans and leases, net of unearned discount	$ 13,573	$ 1,500	$ 746
Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	631	83	134
Pre-modification Recorded Investment	$ 202,985	$ 21,695	$ 34,798
Loans and leases, net of unearned discount	$ 207,517	$ 22,726	$ 38,072
Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	30	6	9
Pre-modification Recorded Investment	$ 7,413	$ 1,409	$ 1,887
Loans and leases, net of unearned discount	$ 8,332	$ 1,443	$ 2,250
Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	259	41	47
Pre-modification Recorded Investment	$ 17,228	$ 4,127	$ 3,952
Loans and leases, net of unearned discount	$ 17,254	$ 4,180	$ 3,979
Recreational Finance [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	428	10	7
Pre-modification Recorded Investment	$ 16,392	$ 265	$ 202
Loans and leases, net of unearned discount	$ 16,392	$ 265	$ 202
Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	2,249	66	73
Pre-modification Recorded Investment	$ 39,951	$ 1,141	$ 1,330
Loans and leases, net of unearned discount	$ 39,951	$ 1,141	1,330
Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1,095
Pre-modification Recorded Investment	$ 7,788
Loans and leases, net of unearned discount	$ 7,788
Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1	2
Pre-modification Recorded Investment	$ 91	$ 1,330
Loans and leases, net of unearned discount	90	1,068
Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	545,415	29,481	90,639
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount			16,870
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	70,671	10,485	50,490
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	204,591	5,193
Principal Deferral [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	13,573		746
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	183,878	10,819	19,962
Principal Deferral [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	7,100	399	827
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	5,882	176	224
Principal Deferral [Member] | Recreational Finance [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	16,388	265	202
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	39,949	1,076	1,318
Principal Deferral [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	3,383
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount		1,068
Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	803		978
Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount			175
Interest Rate Reduction [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	298		803
Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	505
Other [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	36,479		10,896
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount			4,686
Other [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	31,605		6,210
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	4,874
Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	223,349	97,543	77,711
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount			9,000
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	97,344	52,871	45,411
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	85,261	26,152
Combination of Concession Types [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount		1,500
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	23,639	11,907	18,110
Combination of Concession Types [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	1,232	1,044	1,423
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	11,372	4,004	3,755
Combination of Concession Types [Member] | Recreational Finance [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	4
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	2	$ 65	$ 12
Combination of Concession Types [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	4,405
Combination of Concession Types [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Loans and leases, net of unearned discount	$ 90