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, 2016 USD ($) Modification	Jun. 30, 2015 USD ($) Modification	Jun. 30, 2016 USD ($) Modification	Jun. 30, 2015 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	216	218	435	368
Pre-modification, Recorded investment	$ 106,670	$ 96,065	$ 141,574	$ 116,197
Post-modification, Recorded investment	104,458	95,987	140,601	113,989
Financial effects of modification, Recorded investment	(2,212)	(78)	(973)	(2,208)
Financial effects of modification, Interest	$ (341)	$ (692)	$ (1,028)	$ (849)
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			1
Pre-modification, Recorded investment			$ 129
Post-modification, Recorded investment			129
Financial effects of modification, Interest			$ (25)
Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			3
Pre-modification, Recorded investment			$ 23,905
Post-modification, Recorded investment			22,958
Financial effects of modification, Recorded investment			$ (947)
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	10	15	26	22
Pre-modification, Recorded investment	$ 2,726	$ 38,983	$ 6,209	$ 42,775
Post-modification, Recorded investment	2,710	37,585	6,158	41,361
Financial effects of modification, Recorded investment	$ (16)	$ (1,398)	$ (51)	$ (1,414)
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	33	30	57	51
Pre-modification, Recorded investment	$ 45,733	$ 16,018	$ 57,304	$ 17,590
Post-modification, Recorded investment	45,657	15,355	58,378	16,912
Financial effects of modification, Recorded investment	$ (76)	$ (663)	$ 1,074	$ (678)
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	1		2
Pre-modification, Recorded investment	$ 23,905	$ 9,252		$ 10,650
Post-modification, Recorded investment	22,958	9,200		10,598
Financial effects of modification, Recorded investment	$ (947)	$ (52)		$ (52)
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	8	12	25	19
Pre-modification, Recorded investment	$ 963	$ 693	$ 2,944	$ 1,414
Post-modification, Recorded investment	1,040	754	3,231	1,496
Financial effects of modification, Recorded investment	$ 77	$ 61	$ 287	$ 82
Principal Deferral [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	2	1	3	1
Pre-modification, Recorded investment	$ 151	$ 161	$ 276	$ 161
Post-modification, Recorded investment	195	$ 161	333	$ 161
Financial effects of modification, Recorded investment	$ 44		$ 57
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1	1	4	2
Pre-modification, Recorded investment	$ 69	$ 1,198	$ 404	$ 1,219
Post-modification, Recorded investment	$ 69	$ 1,198	$ 404	$ 1,219
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	44	63	92	98
Pre-modification, Recorded investment	$ 158	$ 615	$ 679	$ 918
Post-modification, Recorded investment	$ 158	$ 615	$ 679	$ 918
Principal Deferral [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	29	27	55	49
Pre-modification, Recorded investment	$ 551	$ 770	$ 925	$ 1,066
Post-modification, Recorded investment	$ 551	$ 770	$ 925	$ 1,066
Principal Deferral [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1		1
Pre-modification, Recorded investment	$ 250		$ 250
Post-modification, Recorded investment	$ 250		$ 250
Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1
Pre-modification, Recorded investment	$ 129
Post-modification, Recorded investment	129
Financial effects of modification, Interest	$ (25)
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		4		7
Pre-modification, Recorded investment		$ 95		$ 137
Post-modification, Recorded investment		95		137
Financial effects of modification, Interest		$ (7)		$ (10)
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	4	1	9	5
Pre-modification, Recorded investment	$ 7,065	$ 436	$ 10,998	$ 2,082
Post-modification, Recorded investment	7,008	436	10,932	2,073
Financial effects of modification, Recorded investment	(57)		(66)	(9)
Financial effects of modification, Interest	$ (31)	$ (53)	$ (66)	$ (105)
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	5	2	12	5
Pre-modification, Recorded investment	$ 15,257	$ 15,889	$ 21,414	$ 25,044
Post-modification, Recorded investment	14,217	17,864	20,169	24,853
Financial effects of modification, Recorded investment	$ (1,040)	1,975	$ (1,245)	(191)
Financial effects of modification, Interest		$ (239)		$ (239)
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	8	9	18	12
Pre-modification, Recorded investment	$ 1,043	$ 961	$ 3,364	$ 1,255
Post-modification, Recorded investment	1,122	1,066	3,491	1,415
Financial effects of modification, Recorded investment	$ 79	105	$ 127	160
Financial effects of modification, Interest		$ (144)		$ (178)
Combination of Concession Types [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		2	5	3
Pre-modification, Recorded investment		$ 424	$ 1,312	$ 634
Post-modification, Recorded investment		426	1,379	636
Financial effects of modification, Recorded investment		2	67	2
Financial effects of modification, Interest		$ (26)	$ (339)	$ (30)
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	31	14	54	19
Pre-modification, Recorded investment	$ 3,737	$ 1,356	$ 6,233	$ 1,552
Post-modification, Recorded investment	3,737	1,356	6,233	1,552
Financial effects of modification, Interest	$ (280)	$ (212)	$ (563)	$ (225)
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		9	8	17
Pre-modification, Recorded investment		$ 138	$ 85	$ 222
Post-modification, Recorded investment		138	85	222
Financial effects of modification, Interest		$ (4)	$ (3)	$ (11)
Combination of Concession Types [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	9	10	17	23
Pre-modification, Recorded investment	$ 49	$ 43	$ 196	$ 267
Post-modification, Recorded investment	49	43	196	267
Financial effects of modification, Interest	$ (5)	$ (7)	$ (32)	$ (32)
Combination of Concession Types [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1		1
Pre-modification, Recorded investment	$ 124		$ 124
Post-modification, Recorded investment	$ 124		$ 124
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1		1
Pre-modification, Recorded investment	$ 4,723		$ 4,723
Post-modification, Recorded investment	4,447		4,447
Financial effects of modification, Recorded investment	$ (276)		$ (276)
Other [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		2		2
Pre-modification, Recorded investment		$ 8,991		$ 8,991
Post-modification, Recorded investment		8,883		8,883
Financial effects of modification, Recorded investment		$ (108)		$ (108)
Other [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	22	13	38	23
Pre-modification, Recorded investment	$ 17	$ 21	$ 55	$ 41
Post-modification, Recorded investment	$ 17	$ 21	$ 55	$ 41
Other [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	2	5	7
Pre-modification, Recorded investment	$ 20	$ 21	$ 45	$ 80
Post-modification, Recorded investment	$ 20	$ 21	$ 45	$ 80