Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) Modification	Mar. 31, 2015 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	219	150
Pre-modification, Recorded investment	$ 34,904	$ 20,132
Post-modification, Recorded investment	36,143	18,002
Financial effects of modification, Recorded investment	1,239	(2,130)
Financial effects of modification, Interest	$ (687)	$ (157)
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	16	7
Pre-modification, Recorded investment	$ 3,483	$ 3,792
Post-modification, Recorded investment	3,448	3,776
Financial effects of modification, Recorded investment	$ (35)	$ (16)
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	24	21
Pre-modification, Recorded investment	$ 11,571	$ 1,572
Post-modification, Recorded investment	12,721	1,557
Financial effects of modification, Recorded investment	$ 1,150	$ (15)
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1
Pre-modification, Recorded investment		$ 1,398
Post-modification, Recorded investment		$ 1,398
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	17	7
Pre-modification, Recorded investment	$ 1,981	$ 721
Post-modification, Recorded investment	2,191	742
Financial effects of modification, Recorded investment	$ 210	$ 21
Principal Deferral [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1
Pre-modification, Recorded investment	$ 125
Post-modification, Recorded investment	138
Financial effects of modification, Recorded investment	$ 13
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	1
Pre-modification, Recorded investment	$ 335	$ 21
Post-modification, Recorded investment	$ 335	$ 21
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	48	35
Pre-modification, Recorded investment	$ 521	$ 303
Post-modification, Recorded investment	$ 521	$ 303
Principal Deferral [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	26	22
Pre-modification, Recorded investment	$ 374	$ 296
Post-modification, Recorded investment	$ 374	$ 296
Interest Rate Reduction [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1
Pre-modification, Recorded investment		$ 99
Post-modification, Recorded investment		99
Financial effects of modification, Interest		$ (19)
Interest Rate Reduction [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		3
Pre-modification, Recorded investment		$ 42
Post-modification, Recorded investment		42
Financial effects of modification, Interest		$ (3)
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	5	4
Pre-modification, Recorded investment	$ 3,933	$ 1,646
Post-modification, Recorded investment	3,924	1,637
Financial effects of modification, Recorded investment	(9)	(9)
Financial effects of modification, Interest	$ (35)	$ (52)
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	7	3
Pre-modification, Recorded investment	$ 6,157	$ 9,155
Post-modification, Recorded investment	5,952	6,989
Financial effects of modification, Recorded investment	$ (205)	$ (2,166)
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	10	3
Pre-modification, Recorded investment	$ 2,321	$ 294
Post-modification, Recorded investment	2,369	349
Financial effects of modification, Recorded investment	$ 48	55
Financial effects of modification, Interest		$ (34)
Combination of Concession Types [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	5	1
Pre-modification, Recorded investment	$ 1,312	$ 210
Post-modification, Recorded investment	1,379	210
Financial effects of modification, Recorded investment	67
Financial effects of modification, Interest	$ (339)	$ (4)
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	23	5
Pre-modification, Recorded investment	$ 2,496	$ 196
Post-modification, Recorded investment	2,496	196
Financial effects of modification, Interest	$ (283)	$ (13)
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	8	8
Pre-modification, Recorded investment	$ 85	$ 84
Post-modification, Recorded investment	85	84
Financial effects of modification, Interest	$ (3)	$ (7)
Combination of Concession Types [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	8	13
Pre-modification, Recorded investment	$ 147	$ 224
Post-modification, Recorded investment	147	224
Financial effects of modification, Interest	$ (27)	$ (25)
Other [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	16	10
Pre-modification, Recorded investment	$ 38	$ 20
Post-modification, Recorded investment	$ 38	$ 20
Other [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	2	5
Pre-modification, Recorded investment	$ 25	$ 59
Post-modification, Recorded investment	$ 25	$ 59