Securities - Fair Value of Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	$ 444,062	$ 319,746
Held-to-maturity, Amortized Cost	187,629	165,767
Gross Unrealized Gains	3,971	5,697
Held-to-maturity, Gross Unrealized Gains	6,636	4,244
Gross Unrealized Losses	(3,051)	(1,679)
Held-to-maturity, Gross Unrealized Losses	(562)	(107)
Available-for-sale Securities, Fair Value	444,982	323,764
Held-to-maturity, Fair Value	193,703	169,904
U.S. Treasury and Federal Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	5,940	26,996
Held-to-maturity, Amortized Cost	5,859	9,804
Gross Unrealized Gains	3	56
Held-to-maturity, Gross Unrealized Gains	93	82
Gross Unrealized Losses	(17)	(229)
Available-for-sale Securities, Fair Value	5,926	26,823
Held-to-maturity, Fair Value	5,952	9,886
State and Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	73,829	46,535
Held-to-maturity, Amortized Cost	146,331	129,595
Gross Unrealized Gains	1,299	1,462
Held-to-maturity, Gross Unrealized Gains	5,375	3,398
Gross Unrealized Losses	(33)	(45)
Held-to-maturity, Gross Unrealized Losses	(253)	(106)
Available-for-sale Securities, Fair Value	75,095	47,952
Held-to-maturity, Fair Value	151,453	132,887
Federal Agency Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	157,291	122,930
Held-to-maturity, Amortized Cost	9,051	4,039
Gross Unrealized Gains	567	975
Held-to-maturity, Gross Unrealized Gains	27	35
Gross Unrealized Losses	(1,655)	(1,045)
Held-to-maturity, Gross Unrealized Losses	(124)	(1)
Available-for-sale Securities, Fair Value	156,203	122,860
Held-to-maturity, Fair Value	8,954	4,073
Federal Agency Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	206,970	122,583
Held-to-maturity, Amortized Cost	26,388	22,329
Gross Unrealized Gains	2,080	3,172
Held-to-maturity, Gross Unrealized Gains	1,141	729
Gross Unrealized Losses	(1,346)	(360)
Held-to-maturity, Gross Unrealized Losses	(185)
Available-for-sale Securities, Fair Value	207,704	125,395
Held-to-maturity, Fair Value	27,344	23,058
Private Labeled Mortgage-backed Pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost		670
Gross Unrealized Gains		19
Available-for-sale Securities, Fair Value		689
Corporate Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	32	32
Gross Unrealized Gains	22	13
Available-for-sale Securities, Fair Value	$ 54	$ 45

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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