Investment Securities - Amount of Securities in Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	$ 216,788	$ 62,697
Less than Twelve Months, Unrealized Losses	(5,412)	(300)
Twelve Months or Longer, Fair value		480
Twelve Months or Longer, Unrealized Losses		(12)
Total, Fair Value	216,788	63,177
Total gross, Unrealized Losses	(5,412)	(312)
U.S. Treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	4,708	4,938
Less than Twelve Months, Unrealized Losses	(258)	(22)
Twelve Months or Longer, Fair value
Twelve Months or Longer, Unrealized Losses
Total, Fair Value	4,708	4,938
Total gross, Unrealized Losses	(258)	(22)
U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	101,813	36,793
Less than Twelve Months, Unrealized Losses	(1,786)	(75)
Twelve Months or Longer, Fair value
Twelve Months or Longer, Unrealized Losses
Total, Fair Value	101,813	36,793
Total gross, Unrealized Losses	(1,786)	(75)
State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	30,233	4,574
Less than Twelve Months, Unrealized Losses	(1,049)	(14)
Twelve Months or Longer, Fair value		480
Twelve Months or Longer, Unrealized Losses		(12)
Total, Fair Value	30,233	5,054
Total gross, Unrealized Losses	(1,049)	(26)
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	29,444
Less than Twelve Months, Unrealized Losses	(274)
Twelve Months or Longer, Fair value
Twelve Months or Longer, Unrealized Losses
Total, Fair Value	29,444
Total gross, Unrealized Losses	(274)
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	4,091	5,006
Less than Twelve Months, Unrealized Losses	(253)	(5)
Twelve Months or Longer, Fair value
Twelve Months or Longer, Unrealized Losses
Total, Fair Value	4,091	5,006
Total gross, Unrealized Losses	(253)	(5)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	46,499	10,410
Less than Twelve Months, Unrealized Losses	(1,792)	(51)
Twelve Months or Longer, Fair value
Twelve Months or Longer, Unrealized Losses
Total, Fair Value	46,499	10,410
Total gross, Unrealized Losses	(1,792)	(51)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value		976
Less than Twelve Months, Unrealized Losses		(133)
Twelve Months or Longer, Fair value
Twelve Months or Longer, Unrealized Losses
Total, Fair Value		976
Total gross, Unrealized Losses		$ (133)