Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 494,429	$ 540,614
Unrealized Gains	14,367	12,411
Unrealized Losses	(2,052)	(6,982)
Fair Value	506,744	546,043
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	136,945	141,300
Unrealized Gains	2,958	1,579
Unrealized Losses	(1)	(1,128)
Fair Value	139,902	141,751
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	153,762	165,828
Unrealized Gains	7,643	6,234
Unrealized Losses	(195)	(243)
Fair Value	161,210	171,819
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	137,639	160,316
Unrealized Gains	1,894	1,060
Unrealized Losses	(511)	(3,394)
Fair Value	139,022	157,982
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,299	19,794
Unrealized Gains	177	165
Unrealized Losses	(1,197)	(1,271)
Fair Value	17,279	18,688
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	800
Unrealized Gains	902	2,613
Unrealized Losses	0	0
Fair Value	1,702	3,413
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	45,964	51,556
Unrealized Gains	793	760
Unrealized Losses	(122)	(907)
Fair Value	46,635	51,409
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,020	1,020
Unrealized Gains	0	0
Unrealized Losses	(26)	(39)
Fair Value	$ 994	$ 981