Loans and Leases - Reserve for Loan and Lease Losses Roll Forward (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($) loan borrowers	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		$ 20,662	$ 24,494	$ 24,746
Charge-offs		(8,496)	(8,850)	(13,619)
Recoveries		1,660	1,411	2,139
Provision (recovery of provision)		3,623	3,607	11,228
Provision for acquired credit impaired loans		179
Ending balance		17,628	20,662	24,494
Commercial, Financial and Agricultural [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		6,920	9,789	11,594
Charge-offs		(4,793)	(2,834)	(3,213)
Recoveries		1,032	247	320
Provision (recovery of provision)		3,259	(282)	1,088
Provision for acquired credit impaired loans		0
Ending balance		6,418	6,920	9,789
Real Estate-Commercial and Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		8,943	8,780	7,507
Charge-offs		(1,895)	(4,363)	(8,667)
Recoveries		200	524	1,104
Provision (recovery of provision)		(684)	4,002	8,836
Provision for acquired credit impaired loans		8
Ending balance		6,572	8,943	8,780
Amount of Loans Charged Off Prior to Being Transferred to Loans Held for Sale	$ 1,300
Number of Loans Charged Off Prior to Being Transferred to Loans Held for Sale | loan	2
Number of Borrowers, Loans Charged Off Prior to Being Transferred to Loans Held for Sale | borrowers	1
Real Estate-Residential Secured for Business Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		763	1,062	639
Charge-offs		(179)	(140)	(112)
Recoveries		28	60	13
Provision (recovery of provision)		43	(219)	522
Provision for acquired credit impaired loans		108
Ending balance		763	763	1,062
Real Estate-Residential and Home Equity Secured for Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		1,124	1,284	980
Charge-offs		(279)	(141)	(195)
Recoveries		10	34	13
Provision (recovery of provision)		657	(53)	486
Provision for acquired credit impaired loans		63
Ending balance		1,575	1,124	1,284
Loans to Individuals [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		360	694	679
Charge-offs		(549)	(796)	(641)
Recoveries		176	265	174
Provision (recovery of provision)		359	197	482
Provision for acquired credit impaired loans		0
Ending balance		346	360	694
Lease Financings [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		985	1,285	1,326
Charge-offs		(801)	(576)	(791)
Recoveries		214	281	515
Provision (recovery of provision)		644	(5)	235
Provision for acquired credit impaired loans		0
Ending balance		1,042	985	1,285
Unallocated [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		1,567	1,600	2,021
Provision (recovery of provision)		(655)	(33)	(421)
Provision for acquired credit impaired loans		0
Ending balance		$ 912	$ 1,567	$ 1,600