Loans and Leases - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Modification	Dec. 31, 2018 USD ($) Modification	Dec. 31, 2017 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	412	557	654
Pre-modification Recorded Investment	$ 143,556	$ 175,583	$ 216,063
Post- modification	$ 127,024	$ 180,224	$ 191,522
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	51	83	83
Pre-modification Recorded Investment	$ 48,315	$ 30,217	$ 44,924
Post- modification	$ 31,345	$ 30,731	$ 40,882
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	150	203	217
Pre-modification Recorded Investment	$ 63,715	$ 102,445	$ 111,036
Post- modification	$ 63,356	$ 102,914	$ 88,663
Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	1	2
Pre-modification Recorded Investment	$ 1,559	$ 752	$ 168
Post- modification	$ 1,500	$ 746	$ 168
Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	83	134	141
Pre-modification Recorded Investment	$ 21,695	$ 34,798	$ 31,827
Post- modification	$ 22,726	$ 38,072	$ 34,607
Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	6	9	20
Pre-modification Recorded Investment	$ 1,409	$ 1,887	$ 4,230
Post- modification	$ 1,443	$ 2,250	$ 4,572
Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	41	47	110
Pre-modification Recorded Investment	$ 4,127	$ 3,952	$ 10,049
Post- modification	$ 4,180	$ 3,979	$ 10,213
Recreational Finance [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	10	7	9
Pre-modification Recorded Investment	$ 265	$ 202	$ 160
Post- modification	$ 265	$ 202	$ 160
Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	66	73	69
Pre-modification Recorded Investment	$ 1,141	$ 1,330	$ 1,378
Post- modification	$ 1,141	1,330	$ 1,378
Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	2		3
Pre-modification Recorded Investment	$ 1,330		$ 12,291
Post- modification	1,068		10,879
Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	29,481	90,639	62,302
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	5,193	16,870	17,039
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	10,485	50,490	25,051
Principal Deferral [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		746	168
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	10,819	19,962	16,633
Principal Deferral [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	399	827	911
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	176	224	1,137
Principal Deferral [Member] | Recreational Finance [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	265	202	160
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	1,076	1,318	1,203
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	1,068
Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		978
Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		175
Interest Rate Reduction [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		803
Other [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		10,896	7,818
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		4,686	868
Other [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Post- modification		6,210	6,459
Other [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Post- modification			491
Combination of Concession Types [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	97,543	77,711	121,402
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	26,152	9,000	22,975
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	52,871	45,411	57,153
Combination of Concession Types [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	1,500
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	11,907	18,110	17,974
Combination of Concession Types [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	1,044	1,423	3,661
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	4,004	3,755	8,585
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Post- modification	$ 65	$ 12	175
Combination of Concession Types [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Post- modification			$ 10,879