Loans and Leases - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Modification	Dec. 31, 2013 Modification	Dec. 31, 2012 Modification
Financing Receivable, Modifications [Line Items]
Number of modifications	760	1,258	1,608
Pre-modification, Recorded Investment	$ 134,351	$ 258,075	$ 256,681
Post-modification, Recorded Investment	130,190	254,352	251,018
Financial Effects of Modification, Recorded Investment	(4,161)	(3,723)	(5,663)
Financial Effects of Modification, Interest	(2,969)	(4,691)	(2,853)
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	95	79	61
Pre-modification, Recorded Investment	29,035	16,389	23,888
Post-modification, Recorded Investment	23,628	16,002	22,456
Financial Effects of Modification, Recorded Investment	(5,407)	(387)	(1,432)
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	39	27	24
Pre-modification, Recorded Investment	19,077	40,639	22,855
Post-modification, Recorded Investment	18,997	40,464	23,059
Financial Effects of Modification, Recorded Investment	(80)	(175)	204
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	2	18	23
Pre-modification, Recorded Investment	1,639	21,423	36,868
Post-modification, Recorded Investment	1,639	20,577	34,740
Financial Effects of Modification, Recorded Investment		(846)	(2,128)
Principal Deferral [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	4	3	6
Pre-modification, Recorded Investment	6,703	590	81,062
Post-modification, Recorded Investment	6,611	521	79,312
Financial Effects of Modification, Recorded Investment	(92)	(69)	(1,750)
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	28	32	36
Pre-modification, Recorded Investment	2,710	3,556	4,643
Post-modification, Recorded Investment	2,905	3,821	4,808
Financial Effects of Modification, Recorded Investment	195	265	165
Principal Deferral [Member] | Residential Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	6	10	7
Pre-modification, Recorded Investment	880	1,900	968
Post-modification, Recorded Investment	963	1,880	989
Financial Effects of Modification, Recorded Investment	83	(20)	21
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	3	10	15
Pre-modification, Recorded Investment	280	859	1,285
Post-modification, Recorded Investment	280	861	1,285
Financial Effects of Modification, Recorded Investment		2
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	208	460	618
Pre-modification, Recorded Investment	3,293	6,148	8,347
Post-modification, Recorded Investment	3,293	6,148	8,347
Principal Deferral [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	33	36	80
Pre-modification, Recorded Investment	245	332	1,201
Post-modification, Recorded Investment	245	332	1,201
Interest Rate Reduction [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications		1
Pre-modification, Recorded Investment		104
Post-modification, Recorded Investment		335
Financial Effects of Modification, Recorded Investment		231
Financial Effects of Modification, Interest		(54)
Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	1		2
Pre-modification, Recorded Investment	255		665
Post-modification, Recorded Investment	252		708
Financial Effects of Modification, Recorded Investment	(3)		43
Financial Effects of Modification, Interest	(48)		(129)
Interest Rate Reduction [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	11		1
Pre-modification, Recorded Investment	1,146		109
Post-modification, Recorded Investment	1,222		109
Financial Effects of Modification, Recorded Investment	76
Financial Effects of Modification, Interest	(152)		(20)
Interest Rate Reduction [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	6	1	1
Pre-modification, Recorded Investment	535	99	144
Post-modification, Recorded Investment	535	99	144
Financial Effects of Modification, Interest	(120)	(8)	(6)
Interest Rate Reduction [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	9	15	22
Pre-modification, Recorded Investment	152	235	328
Post-modification, Recorded Investment	152	235	328
Financial Effects of Modification, Interest	(12)	(22)	(24)
Interest Rate Reduction [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	4	1	22
Pre-modification, Recorded Investment	293	12	515
Post-modification, Recorded Investment	293	12	515
Financial Effects of Modification, Interest	(63)	(2)	(85)
Other [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	3	4	3
Pre-modification, Recorded Investment	29,912	50,433	2,967
Post-modification, Recorded Investment	31,604	50,924	3,052
Financial Effects of Modification, Recorded Investment	1,692	491	85
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	1	2
Pre-modification, Recorded Investment	650	449
Post-modification, Recorded Investment		475
Financial Effects of Modification, Recorded Investment	(650)	26
Other [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications		1
Pre-modification, Recorded Investment		4,039
Post-modification, Recorded Investment		3,888
Financial Effects of Modification, Recorded Investment		(151)
Other [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	1	1
Pre-modification, Recorded Investment	188	195
Post-modification, Recorded Investment	188	195
Other [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications		1
Pre-modification, Recorded Investment		106
Post-modification, Recorded Investment		106
Other [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	42	78	67
Pre-modification, Recorded Investment	255	339	300
Post-modification, Recorded Investment	255	339	300
Other [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	1	2	13
Pre-modification, Recorded Investment	45	14	54
Post-modification, Recorded Investment	45	14	54
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	7	11	5
Pre-modification, Recorded Investment	19,167	6,229	628
Post-modification, Recorded Investment	19,030	5,578	740
Financial Effects of Modification, Recorded Investment	(137)	(651)	112
Financial Effects of Modification, Interest	(20)	(458)	(102)
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	7	9	7
Pre-modification, Recorded Investment	1,152	2,649	1,637
Post-modification, Recorded Investment	1,198	3,040	1,656
Financial Effects of Modification, Recorded Investment	46	391	19
Financial Effects of Modification, Interest	(264)	(250)	(351)
Combination of Concession Types [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications		3	7
Pre-modification, Recorded Investment		15,580	37,602
Post-modification, Recorded Investment		15,514	36,148
Financial Effects of Modification, Recorded Investment		(66)	(1,454)
Financial Effects of Modification, Interest		(535)
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	30	61	62
Pre-modification, Recorded Investment	4,211	73,940	12,886
Post-modification, Recorded Investment	4,287	70,854	13,146
Financial Effects of Modification, Recorded Investment	76	(3,086)	260
Financial Effects of Modification, Interest	(483)	(924)	(657)
Combination of Concession Types [Member] | Residential Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	21	19	38
Pre-modification, Recorded Investment	3,806	2,826	8,525
Post-modification, Recorded Investment	3,846	3,148	8,717
Financial Effects of Modification, Recorded Investment	40	322	192
Financial Effects of Modification, Interest	(386)	(790)	(159)
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	47	28	29
Pre-modification, Recorded Investment	5,031	2,190	2,332
Post-modification, Recorded Investment	5,031	2,190	2,332
Financial Effects of Modification, Interest	(560)	(270)	(368)
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	81	225	375
Pre-modification, Recorded Investment	1,189	2,552	5,857
Post-modification, Recorded Investment	1,189	2,552	5,857
Financial Effects of Modification, Interest	(100)	(191)	(684)
Combination of Concession Types [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications	70	120	84
Pre-modification, Recorded Investment	2,502	4,248	1,015
Post-modification, Recorded Investment	2,502	4,248	1,015
Financial Effects of Modification, Interest	$ (761)	$ (1,187)	$ (268)