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
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	$ 48,574		$ 52,089
Without a related allowance, Unpaid Principal Balance	61,489		67,122
Without a related allowance recorded, Related Allowance	0		0
With a related allowance recorded, Recorded Investment	80		767
With a related allowance recorded, Unpaid Principal Balance	80		1,469
With a related allowance recorded, Related Allowance	65		97
Impaired Financing Receivable, Recorded Investment, Total	48,654		52,856
Impaired Financing Receivable, Unpaid Principal Balance, Total	61,569		68,591
Impaired Financing Receivable, Related Allowance	65		97
With a related allowance recorded, Average Recorded Investment	83	4,480
With a related allowance recorded, Interest Income Recognized	2	0
Without a related allowance recorded, Average Recorded Investment	50,068	70,962
Without a related allowance recorded, Interest Income Recognized	383	503
Impaired Financing Receivable, Average Recorded Investment, Total	50,151	75,442
Impaired Financing Receivable, Interest Income Recognized, Total	385	503
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	22,219		26,968
Without a related allowance, Unpaid Principal Balance	30,211		35,474
Without a related allowance recorded, Related Allowance	0		0
With a related allowance recorded, Recorded Investment	0		0
With a related allowance recorded, Unpaid Principal Balance	0		0
With a related allowance recorded, Related Allowance	0		0
Impaired Financing Receivable, Recorded Investment, Total	22,219		26,968
Impaired Financing Receivable, Unpaid Principal Balance, Total	30,211		35,474
Impaired Financing Receivable, Related Allowance	0		0
With a related allowance recorded, Average Recorded Investment	0	4,480
With a related allowance recorded, Interest Income Recognized	0	0
Without a related allowance recorded, Average Recorded Investment	23,539	31,406
Without a related allowance recorded, Interest Income Recognized	167	241
Impaired Financing Receivable, Average Recorded Investment, Total	23,539	35,886
Impaired Financing Receivable, Interest Income Recognized, Total	167	241
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	9,766		9,580
Without a related allowance, Unpaid Principal Balance	9,893		9,703
Without a related allowance recorded, Related Allowance	0		0
With a related allowance recorded, Recorded Investment	0		0
With a related allowance recorded, Unpaid Principal Balance	0		0
With a related allowance recorded, Related Allowance	0		0
Impaired Financing Receivable, Recorded Investment, Total	9,766		9,580
Impaired Financing Receivable, Unpaid Principal Balance, Total	9,893		9,703
Impaired Financing Receivable, Related Allowance	0		0
With a related allowance recorded, Average Recorded Investment	0	0
With a related allowance recorded, Interest Income Recognized	0	0
Without a related allowance recorded, Average Recorded Investment	9,826	12,446
Without a related allowance recorded, Interest Income Recognized	55	69
Impaired Financing Receivable, Average Recorded Investment, Total	9,826	12,446
Impaired Financing Receivable, Interest Income Recognized, Total	55	69
Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	8,321		7,391
Without a related allowance, Unpaid Principal Balance	12,008		12,353
Without a related allowance recorded, Related Allowance	0		0
With a related allowance recorded, Recorded Investment	0		681
With a related allowance recorded, Unpaid Principal Balance	0		1,383
With a related allowance recorded, Related Allowance	0		25
Impaired Financing Receivable, Recorded Investment, Total	8,321		8,072
Impaired Financing Receivable, Unpaid Principal Balance, Total	12,008		13,736
Impaired Financing Receivable, Related Allowance	0		25
With a related allowance recorded, Average Recorded Investment	0	0
With a related allowance recorded, Interest Income Recognized	0	0
Without a related allowance recorded, Average Recorded Investment	8,324	17,332
Without a related allowance recorded, Interest Income Recognized	57	134
Impaired Financing Receivable, Average Recorded Investment, Total	8,324	17,332
Impaired Financing Receivable, Interest Income Recognized, Total	57	134
Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	8,150		8,026
Without a related allowance, Unpaid Principal Balance	9,257		9,464
Without a related allowance recorded, Related Allowance	0		0
With a related allowance recorded, Recorded Investment	50		53
With a related allowance recorded, Unpaid Principal Balance	50		53
With a related allowance recorded, Related Allowance	50		53
Impaired Financing Receivable, Recorded Investment, Total	8,200		8,079
Impaired Financing Receivable, Unpaid Principal Balance, Total	9,307		9,517
Impaired Financing Receivable, Related Allowance	50		53
With a related allowance recorded, Average Recorded Investment	51	0
With a related allowance recorded, Interest Income Recognized	1	0
Without a related allowance recorded, Average Recorded Investment	8,258	9,680
Without a related allowance recorded, Interest Income Recognized	103	59
Impaired Financing Receivable, Average Recorded Investment, Total	8,309	9,680
Impaired Financing Receivable, Interest Income Recognized, Total	104	59
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Without a related allowance recorded, Recorded Investment	118		124
Without a related allowance, Unpaid Principal Balance	120		128
Without a related allowance recorded, Related Allowance	0		0
With a related allowance recorded, Recorded Investment	30		33
With a related allowance recorded, Unpaid Principal Balance	30		33
With a related allowance recorded, Related Allowance	15		19
Impaired Financing Receivable, Recorded Investment, Total	148		157
Impaired Financing Receivable, Unpaid Principal Balance, Total	150		161
Impaired Financing Receivable, Related Allowance	15		19
With a related allowance recorded, Average Recorded Investment	32	0
With a related allowance recorded, Interest Income Recognized	1	0
Without a related allowance recorded, Average Recorded Investment	121	98
Without a related allowance recorded, Interest Income Recognized	1	0
Impaired Financing Receivable, Average Recorded Investment, Total	153	98
Impaired Financing Receivable, Interest Income Recognized, Total	$ 2	$ 0