Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) Modification	Jun. 30, 2020 USD ($) Modification	Jun. 30, 2021 USD ($) Modification	Jun. 30, 2020 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	492	2,394	1,347	2,490
Pre-modification Recorded Investment	$ 254,305	$ 152,872	$ 385,937	$ 219,374
post modification recorded investment	252,836	143,300	382,797	209,817
Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	54,746	69,139	140,262	82,158
Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment		333		333
Other
Financing Receivable, Modifications [Line Items]
post modification recorded investment	28,578	36,405	30,792	36,405
Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 169,512	$ 37,423	$ 211,743	$ 90,921
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	89	135	182	167
Pre-modification Recorded Investment	$ 70,749	$ 55,136	$ 124,482	$ 67,828
post modification recorded investment	70,448	54,670	123,605	66,723
Commercial, Financial, Leasing, etc. [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	11,439	17,551	36,092	22,617
Commercial, Financial, Leasing, etc. [Member] | Other
Financing Receivable, Modifications [Line Items]
post modification recorded investment	222	31,605	222	31,605
Commercial, Financial, Leasing, etc. [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 58,787	$ 5,514	$ 87,291	$ 12,501
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	35	46	68	56
Pre-modification Recorded Investment	$ 143,141	$ 41,872	$ 170,011	$ 81,514
post modification recorded investment	142,161	31,992	167,957	69,315
Commercial Real Estate [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	7,370	10,511	18,530	11,866
Commercial Real Estate [Member] | Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment		333		333
Commercial Real Estate [Member] | Other
Financing Receivable, Modifications [Line Items]
post modification recorded investment	28,356	4,800	30,570	4,800
Commercial Real Estate [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 106,435	$ 16,348	$ 118,857	$ 52,316
Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1		1
Pre-modification Recorded Investment		$ 91		$ 91
post modification recorded investment		90		90
Residential Builder and Developer [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment		$ 90		$ 90
Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3		3
Pre-modification Recorded Investment	$ 542		$ 542
post modification recorded investment	532		532
Other Commercial Construction [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 532		$ 532
Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	117	25	240	52
Pre-modification Recorded Investment	$ 34,041	$ 8,872	$ 73,624	$ 19,050
post modification recorded investment	33,863	9,634	73,537	21,858
Residential [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	29,573	3,101	68,130	6,348
Residential [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 4,290	$ 6,533	$ 5,407	$ 15,510
Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	16	120	42	126
Pre-modification Recorded Investment	$ 1,970	$ 7,571	$ 3,685	$ 8,309
post modification recorded investment	1,970	7,584	3,630	8,330
Home Equity Lines and Loans [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 1,970	147	3,456	559
Home Equity Lines and Loans [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment		$ 7,437	$ 174	$ 7,771
Recreational Finance [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	34	271	106	274
Pre-modification Recorded Investment	$ 1,119	$ 10,795	$ 3,331	$ 10,885
post modification recorded investment	1,119	10,795	3,331	10,885
Recreational Finance [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 1,119	$ 10,795	$ 3,331	$ 10,885
Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	94	1,461	370	1,470
Pre-modification Recorded Investment	$ 1,502	$ 26,352	$ 6,471	$ 26,534
post modification recorded investment	1,502	26,352	6,471	26,534
Automobile [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 1,502	$ 26,352	6,457	$ 26,534
Automobile [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment			$ 14
Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	101		323
Pre-modification Recorded Investment	$ 836		$ 2,270
post modification recorded investment	836		2,270
Other [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 836		$ 2,270
Other
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		335		335
Pre-modification Recorded Investment		$ 2,183		$ 2,183
post modification recorded investment		2,183		2,183
Other | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment		682		682
Other | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment		$ 1,501		$ 1,501
Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3		13	9
Pre-modification Recorded Investment	$ 405		$ 1,521	$ 2,980
post modification recorded investment	405		1,464	3,899
Residential Limited Documentation [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment	$ 405		$ 1,464	2,667
Residential Limited Documentation [Member] | Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
post modification recorded investment				$ 1,232