Investment Securities - Disclosure Regarding Length of Time on Investment Securities with Temporary Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	$ 90,051	$ 135,141
Less than 12 months, Gross unrealized losses	(2,058)	(5,518)
12 months or longer, Fair value	30,693	19,051
12 months or longer, Gross unrealized losses	(1,554)	(1,822)
Total, Fair value	120,744	154,192
Total, Gross unrealized losses	(3,612)	(7,340)
Agency Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	4,117	5,766
Less than 12 months, Gross unrealized losses	(38)	(66)
12 months or longer, Fair value	493	0
12 months or longer, Gross unrealized losses	(7)	0
Total, Fair value	4,610	5,766
Total, Gross unrealized losses	(45)	(66)
State and Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	81,597	123,988
Less than 12 months, Gross unrealized losses	(1,988)	(5,376)
12 months or longer, Fair value	28,906	19,051
12 months or longer, Gross unrealized losses	(1,535)	(1,822)
Total, Fair value	110,503	143,039
Total, Gross unrealized losses	(3,523)	(7,198)
Corporate Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	4,337	5,387
Less than 12 months, Gross unrealized losses	(32)	(76)
12 months or longer, Fair value	1,294	0
12 months or longer, Gross unrealized losses	(12)	0
Total, Fair value	5,631	5,387
Total, Gross unrealized losses	$ (44)	$ (76)