Loans and Allowance for Loan Losses - Activity in All by Class of 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
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 39,924	$ 38,664	$ 39,034	$ 38,725
Charge- offs	(681)	(347)	(1,155)	(880)
Recoveries	925	149	1,071	321
Net charge- offs	244	(198)	(84)	(559)
Provisions charged to operations	3,129	516	4,347	816
Balance at end of period	43,297	38,982	43,297	38,982
Non-residential real estate owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	5,012	4,866	4,827	5,104
Charge- offs	(18)	(2)	(22)	(2)
Recoveries	34	1	65	16
Net charge- offs	16	(1)	43	14
Provisions charged to operations	213	(151)	371	(404)
Balance at end of period	5,241	4,714	5,241	4,714
Non-residential real estate other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	10,685	10,465	11,026	9,865
Charge- offs		(1)		(19)
Recoveries		6	3	10
Net charge- offs		5	3	(9)
Provisions charged to operations	553	396	209	1,010
Balance at end of period	11,238	10,866	11,238	10,866
Residential real estate permanent mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	3,237	2,756	2,825	2,781
Charge- offs	(32)	(40)	(162)	(96)
Recoveries	31	4	41	15
Net charge- offs	(1)	(36)	(121)	(81)
Provisions charged to operations	74	13	606	33
Balance at end of period	3,310	2,733	3,310	2,733
Residential real estate all other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	6,485	7,165	6,708	7,034
Charge- offs	(44)	(59)	(93)	(154)
Recoveries	10	25	14	27
Net charge- offs	(34)	(34)	(79)	(127)
Provisions charged to operations	364	218	186	442
Balance at end of period	6,815	7,349	6,815	7,349
Non-consumer non-real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	9,703	8,982	8,977	9,385
Charge- offs	(61)	(69)	(131)	(105)
Recoveries	16	18	30	49
Net charge- offs	(45)	(51)	(101)	(56)
Provisions charged to operations	2,309	(180)	3,091	(578)
Balance at end of period	11,967	8,751	11,967	8,751
Consumer non-real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	2,573	2,384	2,556	2,451
Charge- offs	(190)	(155)	(331)	(295)
Recoveries	46	61	108	137
Net charge- offs	(144)	(94)	(223)	(158)
Provisions charged to operations	216	99	312	96
Balance at end of period	2,645	2,389	2,645	2,389
Other loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	2,072	1,822	1,991	1,885
Charge- offs	(188)	(20)	(251)	(159)
Recoveries	110	31	127	31
Net charge- offs	(78)	11	(124)	(128)
Provisions charged to operations	(1)	128	126	204
Balance at end of period	1,993	1,961	1,993	1,961
Acquired loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	157	224	124	220
Charge- offs	(148)	(1)	(165)	(50)
Recoveries	678	3	683	36
Net charge- offs	530	2	518	(14)
Provisions charged to operations	(599)	(7)	(554)	13
Balance at end of period	$ 88	$ 219	$ 88	$ 219