Allowance for Loan Losses - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	$ 63,560	$ 72,126	$ 66,241
Unpaid principal, With no related allowance recorded	75,010	85,594	82,489
Average recorded Investment, With no related allowance recorded	68,975	77,271	71,116
Interest income Recognized, With no related allowance recorded	371	386	1,758
Recorded investment, With an allowance recorded	14,641	15,718	12,855
Unpaid principal, With an allowance recorded	19,810	21,176	13,896
Related allowance, With an allowance recorded	3,495	4,464	3,558
Average recorded Investment, With an allowance recorded	14,781	16,089	15,050
Interest income Recognized, With an allowance recorded	71	104	427
PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	1,325	1,614	1,562
Unpaid principal, With no related allowance recorded	3,520	3,689	3,825
Average recorded Investment, With no related allowance recorded	1,348	1,725	1,421
Interest income Recognized, With no related allowance recorded	8	4	39
Recorded investment, With an allowance recorded	774	782	578
Unpaid principal, With an allowance recorded	792	813	599
Related allowance, With an allowance recorded	446	581	417
Average recorded Investment, With an allowance recorded	714	707	716
Interest income Recognized, With an allowance recorded	4	9	16
RE Mortgage [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	4,349	4,017	4,366
Unpaid principal, With no related allowance recorded	6,532	6,192	6,489
Average recorded Investment, With no related allowance recorded	4,206	3,769	4,123
Interest income Recognized, With no related allowance recorded	14	7	74
Recorded investment, With an allowance recorded	2,457	2,025	2,630
Unpaid principal, With an allowance recorded	2,528	2,252	2,689
Related allowance, With an allowance recorded	502	447	648
Average recorded Investment, With an allowance recorded	2,353	2,446	2,245
Interest income Recognized, With an allowance recorded	13	15	85
RE Mortgage [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	84		148
Unpaid principal, With no related allowance recorded	84		158
Average recorded Investment, With no related allowance recorded	58		37
Interest income Recognized, With no related allowance recorded	2		6
Recorded investment, With an allowance recorded	432	197	198
Unpaid principal, With an allowance recorded	443	224	207
Related allowance, With an allowance recorded	164	32	128
Average recorded Investment, With an allowance recorded	334	198	275
Interest income Recognized, With an allowance recorded	2	1	3
RE Mortgage [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	53,996	57,206	53,352
Unpaid principal, With no related allowance recorded	59,159	62,263	58,894
Average recorded Investment, With no related allowance recorded	57,403	61,619	58,205
Interest income Recognized, With no related allowance recorded	340	362	1,154
Recorded investment, With an allowance recorded	4,599	5,816	5,296
Unpaid principal, With an allowance recorded	5,240	6,095	5,659
Related allowance, With an allowance recorded	855	1,296	1,084
Average recorded Investment, With an allowance recorded	5,773	4,537	6,077
Interest income Recognized, With an allowance recorded	25	47	168
RE Mortgage [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	870	1,271	1,139
Unpaid principal, With no related allowance recorded	3,044	3,300	3,323
Average recorded Investment, With no related allowance recorded	905	1,370	1,005
Interest income Recognized, With no related allowance recorded		4	32
Recorded investment, With an allowance recorded	148	519	149
Unpaid principal, With an allowance recorded	149	519	149
Related allowance, With an allowance recorded	113	508	114
Average recorded Investment, With an allowance recorded	157	420	250
Interest income Recognized, With an allowance recorded	2	7	9
Home equity lines of credit [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	3,386	5,138	3,710
Unpaid principal, With no related allowance recorded	6,833	8,437	7,299
Average recorded Investment, With no related allowance recorded	3,972	4,690	4,410
Interest income Recognized, With no related allowance recorded	2	5	25
Recorded investment, With an allowance recorded	3,214	3,244	2,779
Unpaid principal, With an allowance recorded	3,449	4,086	3,053
Related allowance, With an allowance recorded	1,228	1,576	968
Average recorded Investment, With an allowance recorded	3,057	4,328	3,064
Interest income Recognized, With an allowance recorded	14	16	86
Home equity lines of credit [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	326	302	227
Unpaid principal, With no related allowance recorded	336	343	287
Average recorded Investment, With no related allowance recorded	339	334	333
Interest income Recognized, With no related allowance recorded	6
Recorded investment, With an allowance recorded	166	37	203
Unpaid principal, With an allowance recorded	172	41	215
Related allowance, With an allowance recorded	166	37	172
Average recorded Investment, With an allowance recorded	195	38	162
Interest income Recognized, With an allowance recorded			3
Home equity loans [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	541	460	552
Unpaid principal, With no related allowance recorded	921	1,110	1,249
Average recorded Investment, With no related allowance recorded	483	411	463
Interest income Recognized, With no related allowance recorded			1
Recorded investment, With an allowance recorded	234	116	226
Unpaid principal, With an allowance recorded	300	166	291
Related allowance, With an allowance recorded	178	50	169
Average recorded Investment, With an allowance recorded	170	142	141
Interest income Recognized, With an allowance recorded	1	1	5
Home equity loans [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded
Unpaid principal, With no related allowance recorded
Average recorded Investment, With no related allowance recorded
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded
Unpaid principal, With an allowance recorded
Related allowance, With an allowance recorded
Average recorded Investment, With an allowance recorded
Interest income Recognized, With an allowance recorded
Auto Indirect [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	45	151	55
Unpaid principal, With no related allowance recorded	82	292	123
Average recorded Investment, With no related allowance recorded	66	157	93
Interest income Recognized, With no related allowance recorded		1	2
Recorded investment, With an allowance recorded	4	25	4
Unpaid principal, With an allowance recorded	5	32	6
Related allowance, With an allowance recorded	1	7	1
Average recorded Investment, With an allowance recorded	7	30	12
Interest income Recognized, With an allowance recorded
Auto Indirect [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded
Unpaid principal, With no related allowance recorded
Average recorded Investment, With no related allowance recorded
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded
Unpaid principal, With an allowance recorded
Related allowance, With an allowance recorded
Average recorded Investment, With an allowance recorded
Interest income Recognized, With an allowance recorded
Other Consumer [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	32	23	16
Unpaid principal, With no related allowance recorded	37	40	21
Average recorded Investment, With no related allowance recorded	21	21	18
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded	5	4	10
Unpaid principal, With an allowance recorded	6	4	10
Related allowance, With an allowance recorded	1	4	5
Average recorded Investment, With an allowance recorded	7	17	7
Interest income Recognized, With an allowance recorded			1
Other Consumer [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	34	41	36
Unpaid principal, With no related allowance recorded	45	46	45
Average recorded Investment, With no related allowance recorded	37	21	39
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded	28	29	28
Unpaid principal, With an allowance recorded	28	29	28
Related allowance, With an allowance recorded	3	4	3
Average recorded Investment, With an allowance recorded	28	51	29
Interest income Recognized, With an allowance recorded		1	1
C&I [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	1,105	4,240	1,648
Unpaid principal, With no related allowance recorded	1,120	5,392	1,665
Average recorded Investment, With no related allowance recorded	1,370	4,239	2,154
Interest income Recognized, With no related allowance recorded	15	11	101
Recorded investment, With an allowance recorded	1,421	1,626	1,517
Unpaid principal, With an allowance recorded	1,509	1,680	1,616
Related allowance, With an allowance recorded	626	823	585
Average recorded Investment, With an allowance recorded	1,766	2,975	1,817
Interest income Recognized, With an allowance recorded	13	19	63
C&I [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	11		12
Unpaid principal, With no related allowance recorded	11		12
Average recorded Investment, With no related allowance recorded	9		7
Interest income Recognized, With no related allowance recorded			1
Recorded investment, With an allowance recorded
Unpaid principal, With an allowance recorded
Related allowance, With an allowance recorded
Average recorded Investment, With an allowance recorded
Interest income Recognized, With an allowance recorded
Construction [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	87	696	2,473
Unpaid principal, With no related allowance recorded	225	1,442	6,611
Average recorded Investment, With no related allowance recorded	1,415	2,125	1,567
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded	2,707	2,713	284
Unpaid principal, With an allowance recorded	6,773	6,680	284
Related allowance, With an allowance recorded	104	219	91
Average recorded Investment, With an allowance recorded	1,497	1,378	1,499
Interest income Recognized, With an allowance recorded	5	5	19
Construction [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded
Unpaid principal, With no related allowance recorded
Average recorded Investment, With no related allowance recorded
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded
Unpaid principal, With an allowance recorded
Related allowance, With an allowance recorded
Average recorded Investment, With an allowance recorded
Interest income Recognized, With an allowance recorded
Construction [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded	19	195	69
Unpaid principal, With no related allowance recorded	101	426	138
Average recorded Investment, With no related allowance recorded	39	240	83
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded		149	109
Unpaid principal, With an allowance recorded		181	288
Related allowance, With an allowance recorded		42	7
Average recorded Investment, With an allowance recorded	151	236	188
Interest income Recognized, With an allowance recorded		1
Construction [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment, With no related allowance recorded
Unpaid principal, With no related allowance recorded
Average recorded Investment, With no related allowance recorded
Interest income Recognized, With no related allowance recorded
Recorded investment, With an allowance recorded
Unpaid principal, With an allowance recorded
Related allowance, With an allowance recorded
Average recorded Investment, With an allowance recorded
Interest income Recognized, With an allowance recorded