Allowance for Loan Losses - Investments in Loans Considered to be Impaired and Related Information on Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	$ 46,141		$ 46,141		$ 52,089
Without a related allowance, Unpaid Principal Balance	57,560		57,560		67,122
Without a related allowance recorded, Related Allowance	0		0		0
With a related allowance recorded, Recorded Investment	68		68		767
With a related allowance recorded, Unpaid Principal Balance	68		68		1,469
With a related allowance recorded, Related Allowance	58		58		97
Impaired Financing Receivable, Recorded Investment, Total	46,209		46,209		52,856
Impaired Financing Receivable, Unpaid Principal Balance, Total	57,628		57,628		68,591
Impaired Financing Receivable, Related Allowance	58		58		97
With a related allowance recorded, Average Recorded Investment	70	2,198	73	3,339
With a related allowance recorded, Interest Income Recognized	1	5	3	5
Without a related allowance recorded, Average Recorded Investment	46,253	68,606	46,719	69,784
Without a related allowance recorded, Interest Income Recognized	374	485	762	988
Impaired Financing Receivable, Average Recorded Investment, Total	46,323	70,804	46,792	73,123
Impaired Financing Receivable, Interest Income Recognized, Total	375	490	765	993
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	21,228		21,228		26,968
Without a related allowance, Unpaid Principal Balance	28,296		28,296		35,474
Without a related allowance recorded, Related Allowance	0		0		0
With a related allowance recorded, Recorded Investment	0		0		0
With a related allowance recorded, Unpaid Principal Balance	0		0		0
With a related allowance recorded, Related Allowance	0		0		0
Impaired Financing Receivable, Recorded Investment, Total	21,228		21,228		26,968
Impaired Financing Receivable, Unpaid Principal Balance, Total	28,296		28,296		35,474
Impaired Financing Receivable, Related Allowance	0		0		0
With a related allowance recorded, Average Recorded Investment	0	2,084	0	3,282
With a related allowance recorded, Interest Income Recognized	0	0	0	0
Without a related allowance recorded, Average Recorded Investment	21,382	30,956	21,980	31,181
Without a related allowance recorded, Interest Income Recognized	159	174	329	415
Impaired Financing Receivable, Average Recorded Investment, Total	21,382	33,040	21,980	34,463
Impaired Financing Receivable, Interest Income Recognized, Total	159	174	329	415
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	9,545		9,545		9,580
Without a related allowance, Unpaid Principal Balance	9,660		9,660		9,703
Without a related allowance recorded, Related Allowance	0		0		0
With a related allowance recorded, Recorded Investment	0		0		0
With a related allowance recorded, Unpaid Principal Balance	0		0		0
With a related allowance recorded, Related Allowance	0		0		0
Impaired Financing Receivable, Recorded Investment, Total	9,545		9,545		9,580
Impaired Financing Receivable, Unpaid Principal Balance, Total	9,660		9,660		9,703
Impaired Financing Receivable, Related Allowance	0		0		0
With a related allowance recorded, Average Recorded Investment	0	0	0	0
With a related allowance recorded, Interest Income Recognized	0	0	0	0
Without a related allowance recorded, Average Recorded Investment	9,317	12,452	9,066	12,449
Without a related allowance recorded, Interest Income Recognized	57	66	114	135
Impaired Financing Receivable, Average Recorded Investment, Total	9,317	12,452	9,066	12,449
Impaired Financing Receivable, Interest Income Recognized, Total	57	66	114	135
Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	8,179		8,179		7,391
Without a related allowance, Unpaid Principal Balance	11,866		11,866		12,353
Without a related allowance recorded, Related Allowance	0		0		0
With a related allowance recorded, Recorded Investment	0		0		681
With a related allowance recorded, Unpaid Principal Balance	0		0		1,383
With a related allowance recorded, Related Allowance	0		0		25
Impaired Financing Receivable, Recorded Investment, Total	8,179		8,179		8,072
Impaired Financing Receivable, Unpaid Principal Balance, Total	11,866		11,866		13,736
Impaired Financing Receivable, Related Allowance	0		0		25
With a related allowance recorded, Average Recorded Investment	0	0	0	0
With a related allowance recorded, Interest Income Recognized	0	0	0	0
Without a related allowance recorded, Average Recorded Investment	8,279	16,376	8,301	16,854
Without a related allowance recorded, Interest Income Recognized	57	87	114	221
Impaired Financing Receivable, Average Recorded Investment, Total	8,279	16,376	8,301	16,854
Impaired Financing Receivable, Interest Income Recognized, Total	57	87	114	221
Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	7,082		7,082		8,026
Without a related allowance, Unpaid Principal Balance	7,629		7,629		9,464
Without a related allowance recorded, Related Allowance	0		0		0
With a related allowance recorded, Recorded Investment	47		47		53
With a related allowance recorded, Unpaid Principal Balance	47		47		53
With a related allowance recorded, Related Allowance	47		47		53
Impaired Financing Receivable, Recorded Investment, Total	7,129		7,129		8,079
Impaired Financing Receivable, Unpaid Principal Balance, Total	7,676		7,676		9,517
Impaired Financing Receivable, Related Allowance	47		47		53
With a related allowance recorded, Average Recorded Investment	48	86	50	43
With a related allowance recorded, Interest Income Recognized	1	4	2	4
Without a related allowance recorded, Average Recorded Investment	7,166	8,708	7,260	9,194
Without a related allowance recorded, Interest Income Recognized	100	156	203	215
Impaired Financing Receivable, Average Recorded Investment, Total	7,214	8,794	7,310	9,237
Impaired Financing Receivable, Interest Income Recognized, Total	101	160	205	219
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	107		107		124
Without a related allowance, Unpaid Principal Balance	109		109		128
Without a related allowance recorded, Related Allowance	0		0		0
With a related allowance recorded, Recorded Investment	21		21		33
With a related allowance recorded, Unpaid Principal Balance	21		21		33
With a related allowance recorded, Related Allowance	11		11		19
Impaired Financing Receivable, Recorded Investment, Total	128		128		157
Impaired Financing Receivable, Unpaid Principal Balance, Total	130		130		161
Impaired Financing Receivable, Related Allowance	11		11		19
With a related allowance recorded, Average Recorded Investment	22	28	23	14
With a related allowance recorded, Interest Income Recognized	0	1	1	1
Without a related allowance recorded, Average Recorded Investment	109	114	112	106
Without a related allowance recorded, Interest Income Recognized	1	2	2	2
Impaired Financing Receivable, Average Recorded Investment, Total	131	142	135	120
Impaired Financing Receivable, Interest Income Recognized, Total	$ 1	$ 3	$ 3	$ 3