Investment Securities - Amount of Securities in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 12,078	$ 15,036
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	(27)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,953	4,987
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(55)	(25)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	17,031	20,023
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(64)	(52)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	159,393	76,626
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,382)	(471)
Twelve Months or Longer, Fair Value	24,996	95,818
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(466)	(1,057)
Total, Fair Value	184,389	172,444
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,848)	(1,528)
Corporate Bonds [Member]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	12,078	15,036
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	(27)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,953	4,987
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(55)	(25)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	17,031	20,023
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(64)	(52)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	72,234	21,949
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,941)	(328)
Twelve Months or Longer, Fair Value	10,669	15,805
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(253)	(287)
Total, Fair Value	82,903	37,754
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,194)	(615)
U.S. Treasuries [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Twelve Months or Longer, Fair Value	4,887	4,845
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(91)	(127)
Total, Fair Value	4,887	4,845
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(91)	(127)
U.S. Government Corporations and Agencies [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	72,157	39,607
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(379)	(80)
Twelve Months or Longer, Fair Value	4,972	62,140
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(28)	(452)
Total, Fair Value	77,129	101,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(407)	(532)
State and Political Subdivisions [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	10,251	10,246
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(49)	(31)
Twelve Months or Longer, Fair Value	1,335	9,303
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12)	(106)
Total, Fair Value	11,586	19,549
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(61)	(137)
Residential Mortgage-Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	4,751	4,824
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(13)	(32)
Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total, Fair Value	4,751	4,824
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(13)	(32)
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Twelve Months or Longer, Fair Value	3,133	3,725
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(82)	(85)
Total, Fair Value	3,133	3,725
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (82)	$ (85)