Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Modification	Sep. 30, 2014 USD ($) Modification	Sep. 30, 2015 USD ($) Modification	Sep. 30, 2014 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	245	154	613	590
Pre-modification, Recorded Investment	$ 23,691	$ 9,009	$ 139,888	$ 98,923
Post-modification, Recorded investment	23,657	8,388	137,646	98,185
Financial effects of modification, Recorded investment	(34)	(621)	(2,242)	(738)
Financial Effects of Modification, Interest	$ (557)	$ (505)	$ (1,406)	$ (2,385)
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	36	15	87	66
Pre-modification, Recorded Investment	$ 7,893	$ 1,305	$ 25,483	$ 20,673
Post-modification, Recorded investment	7,419	1,300	24,331	20,499
Financial effects of modification, Recorded investment	$ (474)	$ (5)	$ (1,152)	$ (174)
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	15	8	37	32
Pre-modification, Recorded Investment	$ 4,230	$ 2,081	$ 47,005	$ 17,452
Post-modification, Recorded investment	4,208	2,068	45,569	17,384
Financial effects of modification, Recorded investment	$ (22)	$ (13)	$ (1,436)	$ (68)
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1	2	2
Pre-modification, Recorded Investment		$ 241	$ 10,650	$ 1,639
Post-modification, Recorded investment		$ 241	10,598	$ 1,639
Financial effects of modification, Recorded investment			$ (52)
Principal Deferral [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	1	3	4
Pre-modification, Recorded Investment	$ 296	$ 145	$ 296	$ 6,703
Post-modification, Recorded investment	390	142	390	6,611
Financial effects of modification, Recorded investment	$ 94	$ (3)	$ 94	$ (92)
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	31	3	50	19
Pre-modification, Recorded Investment	$ 3,540	$ 98	$ 4,954	$ 1,842
Post-modification, Recorded investment	3,743	97	5,239	1,926
Financial effects of modification, Recorded investment	$ 203	$ (1)	$ 285	$ 84
Principal Deferral [Member] | Residential Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1		2	5
Pre-modification, Recorded Investment	$ 265		$ 426	$ 828
Post-modification, Recorded investment	276		437	900
Financial effects of modification, Recorded investment	$ 11		$ 11	$ 72
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	4		6	3
Pre-modification, Recorded Investment	$ 727		$ 1,946	$ 280
Post-modification, Recorded investment	$ 727		$ 1,946	$ 280
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	35	45	133	168
Pre-modification, Recorded Investment	$ 316	$ 1,003	$ 1,234	$ 2,599
Post-modification, Recorded investment	$ 316	$ 1,003	$ 1,234	$ 2,599
Principal Deferral [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	24	6	73	21
Pre-modification, Recorded Investment	$ 352	$ 48	$ 1,418	$ 141
Post-modification, Recorded investment	$ 352	$ 48	$ 1,418	$ 141
Other [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			2	1
Pre-modification, Recorded Investment			$ 8,991	$ 19,593
Post-modification, Recorded investment			8,883	$ 19,593
Financial effects of modification, Recorded investment			$ (108)
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1		1
Pre-modification, Recorded Investment		$ 650		$ 650
Financial effects of modification, Recorded investment		$ (650)		$ (650)
Other [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1		1	1
Pre-modification, Recorded Investment	$ 267		$ 267	$ 188
Post-modification, Recorded investment	$ 267		$ 267	$ 188
Other [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	15	7	38	26
Pre-modification, Recorded Investment	$ 93	$ 96	$ 134	$ 204
Post-modification, Recorded investment	$ 93	$ 96	$ 134	$ 204
Other [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	5		12	1
Pre-modification, Recorded Investment	$ 33		$ 113	$ 45
Post-modification, Recorded investment	$ 33		$ 113	$ 45
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1		6	5
Pre-modification, Recorded Investment	$ 31		$ 25,075	$ 9,836
Post-modification, Recorded investment	31		24,884	9,766
Financial effects of modification, Recorded investment			(191)	(70)
Financial Effects of Modification, Interest	$ (6)		$ (245)	$ (14)
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1	4	6	6
Pre-modification, Recorded Investment	$ 1,156	$ 483	$ 3,238	$ 892
Post-modification, Recorded investment	1,169	478	3,242	940
Financial effects of modification, Recorded investment	13	(5)	4	48
Financial Effects of Modification, Interest	$ (54)	$ (95)	$ (159)	$ (208)
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	10	8	22	30
Pre-modification, Recorded Investment	$ 1,296	$ 1,100	$ 2,551	$ 4,211
Post-modification, Recorded investment	1,380	1,136	2,795	4,287
Financial effects of modification, Recorded investment	84	36	244	76
Financial Effects of Modification, Interest	$ (178)	$ (135)	$ (356)	$ (483)
Combination of Concession Types [Member] | Residential Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	4	3	7	19
Pre-modification, Recorded Investment	$ 605	$ 349	$ 1,239	$ 3,101
Post-modification, Recorded investment	662	369	1,298	3,134
Financial effects of modification, Recorded investment	57	20	59	33
Financial Effects of Modification, Interest	$ (91)	$ (64)	$ (121)	$ (345)
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	22	5	41	41
Pre-modification, Recorded Investment	$ 2,003	$ 519	$ 3,555	$ 4,147
Post-modification, Recorded investment	2,003	519	3,555	4,147
Financial Effects of Modification, Interest	$ (199)	$ (67)	$ (424)	$ (443)
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	25	19	42	65
Pre-modification, Recorded Investment	$ 471	$ 348	$ 693	$ 939
Post-modification, Recorded investment	471	348	693	939
Financial Effects of Modification, Interest	$ (17)	$ (21)	$ (28)	$ (83)
Combination of Concession Types [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	12	24	35	57
Pre-modification, Recorded Investment	$ 117	$ 511	$ 384	$ 1,883
Post-modification, Recorded investment	117	511	384	1,883
Financial Effects of Modification, Interest	$ (12)	$ (121)	$ (44)	$ (585)
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] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification				1
Pre-modification, Recorded Investment				$ 255
Post-modification, Recorded investment				252
Financial effects of modification, Recorded investment				(3)
Financial Effects of Modification, Interest				$ (48)
Interest Rate Reduction [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification				1
Pre-modification, Recorded Investment				$ 98
Post-modification, Recorded investment				104
Financial effects of modification, Recorded investment				6
Financial Effects of Modification, Interest				$ (32)
Interest Rate Reduction [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification				5
Pre-modification, Recorded Investment				$ 341
Post-modification, Recorded investment				341
Financial Effects of Modification, Interest				$ (76)
Interest Rate Reduction [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		3	7	6
Pre-modification, Recorded Investment		$ 30	$ 137	$ 90
Post-modification, Recorded investment		30	137	90
Financial Effects of Modification, Interest		$ (2)	$ (10)	$ (5)
Interest Rate Reduction [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1		4
Pre-modification, Recorded Investment		$ 2		$ 293
Post-modification, Recorded investment		$ 2		293
Financial Effects of Modification, Interest				$ (63)