Securities Available-for-Sale - Summary of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 526,762	$ 404,977
Gross Unrealized Gains	542	979
Gross Unrealized Losses	1,172	1,333
Total, Fair Value	526,132	404,623
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	1,999
Gross Unrealized Losses		10
Total, Fair Value	2,000	1,989
U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,000
Gross Unrealized Gains	9
Total, Fair Value	15,009
SBA Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	58,496	5,983
Gross Unrealized Gains	11	8
Gross Unrealized Losses	162	2
Total, Fair Value	58,345	5,989
U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	264,545	232,967
Gross Unrealized Gains	346	859
Gross Unrealized Losses	437	300
Total, Fair Value	264,454	233,526
Privately Issued Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,190	1,437
Gross Unrealized Gains	2	10
Gross Unrealized Losses	15	13
Total, Fair Value	1,177	1,434
Obligations Issued by States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	180,315	157,838
Gross Unrealized Losses	404	878
Total, Fair Value	179,911	156,960
Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,100	4,600
Gross Unrealized Gains	15	3
Gross Unrealized Losses	154	130
Total, Fair Value	4,961	4,473
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116	153
Gross Unrealized Gains	159	99
Total, Fair Value	$ 275	$ 252