Investment Securities - Amount of Securities in Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
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	$ 13,189	$ 19,942
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(39)	(264)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,993	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(21)	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	18,182	19,942
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(60)	(264)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	51,629	196,846
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(418)	(5,148)
Twelve Months or Longer, Fair Value	112,871	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,643)	0
Total, Fair Value	164,500	196,846
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,061)	(5,148)
U.S. Treasuries [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	0	4,708
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(258)
Twelve Months or Longer, Fair Value	4,790	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(181)	0
Total, Fair Value	4,790	4,708
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(181)	(258)
U.S. Government Corporations and Agencies [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	19,948	101,813
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(52)	(1,786)
Twelve Months or Longer, Fair Value	77,353	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(800)	0
Total, Fair Value	97,301	101,813
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(852)	(1,786)
State and Political Subdivisions [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	1,883	30,233
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(4)	(1,049)
Twelve Months or Longer, Fair Value	11,146	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(148)	0
Total, Fair Value	13,029	30,233
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(152)	(1,049)
Residential Mortgage-Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	12,391	29,444
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(129)	(274)
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	12,391	29,444
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(129)	(274)
Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	0	4,091
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(253)
Twelve Months or Longer, Fair Value	3,807	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(123)	0
Total, Fair Value	3,807	4,091
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(123)	(253)
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	13,189	19,942
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(39)	(264)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,993	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(21)	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	18,182	19,942
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(60)	(264)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than Twelve Months, Fair Value	17,407	26,557
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(233)	(1,528)
Twelve Months or Longer, Fair Value	15,775	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(391)	0
Total, Fair Value	33,182	26,557
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (624)	$ (1,528)