Loans and Allowance for Loan Losses - Activity in All by Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 42,621	$ 43,297	$ 40,889	$ 39,034
Charge- offs	(3,174)	(926)	(4,202)	(2,081)
Recoveries	99	211	254	1,282
Net charge- offs	(3,075)	(715)	(3,948)	(799)
Provisions charged to operations	1,424	(3,115)	4,029	1,232
Balance at end of period	40,970	39,467	40,970	39,467
Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,503	5,241	4,406	4,827
Charge- offs			(1)	(22)
Recoveries		20	1	85
Net charge- offs		20		63
Provisions charged to operations	36	(798)	133	(427)
Balance at end of period	4,539	4,463	4,539	4,463
Non-residential Real Estate Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	9,880	11,238	9,616	11,026
Charge- offs	(708)	(29)	(708)	(29)
Recoveries	1	45	2	48
Net charge- offs	(707)	16	(706)	19
Provisions charged to operations	814	(1,784)	1,077	(1,575)
Balance at end of period	9,987	9,470	9,987	9,470
Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	3,110	3,310	2,948	2,825
Charge- offs	(28)	(12)	(124)	(174)
Recoveries	15	18	29	59
Net charge- offs	(13)	6	(95)	(115)
Provisions charged to operations	(26)	(464)	218	142
Balance at end of period	3,071	2,852	3,071	2,852
Residential Real Estate All Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	6,485	6,815	6,269	6,708
Charge- offs	(48)	(23)	(123)	(116)
Recoveries	4	9	13	23
Net charge- offs	(44)	(14)	(110)	(93)
Provisions charged to operations	168	(649)	450	(463)
Balance at end of period	6,609	6,152	6,609	6,152
Non-consumer Non-real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	13,713	11,967	12,771	8,977
Charge- offs	(2,180)	(391)	(2,349)	(522)
Recoveries	38	21	76	51
Net charge- offs	(2,142)	(370)	(2,273)	(471)
Provisions charged to operations	86	412	1,159	3,503
Balance at end of period	11,657	12,009	11,657	12,009
Consumer Non-real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	2,499	2,645	2,404	2,556
Charge- offs	(152)	(177)	(382)	(508)
Recoveries	35	58	90	166
Net charge- offs	(117)	(119)	(292)	(342)
Provisions charged to operations	160	(132)	430	180
Balance at end of period	2,542	2,394	2,542	2,394
Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	2,431	1,993	2,359	1,991
Charge- offs	(20)	(93)	(283)	(344)
Recoveries	6	8	15	135
Net charge- offs	(14)	(85)	(268)	(209)
Provisions charged to operations	134	219	460	345
Balance at end of period	2,551	2,127	2,551	2,127
Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		88	116	124
Charge- offs	(38)	(201)	(232)	(366)
Recoveries		32	28	715
Net charge- offs	(38)	(169)	(204)	349
Provisions charged to operations	52	$ 81	102	$ (473)
Balance at end of period	$ 14		$ 14