Investment Securities - Disclosure Regarding Length of Time on Investment Securities with Temporary Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	$ 107,356	$ 135,141
Less than 12 months, Gross unrealized losses	(642)	(5,518)
12 months or longer, Fair value	71,166	19,051
12 months or longer, Gross unrealized losses	(1,725)	(1,822)
Total, Fair value	178,522	154,192
Total, Gross unrealized losses	(2,367)	(7,340)
Agency Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	644	5,766
Less than 12 months, Gross unrealized losses	(1)	(66)
12 months or longer, Fair value	2,960	0
12 months or longer, Gross unrealized losses	(20)	0
Total, Fair value	3,604	5,766
Total, Gross unrealized losses	(21)	(66)
State and Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	105,965	123,988
Less than 12 months, Gross unrealized losses	(638)	(5,376)
12 months or longer, Fair value	65,634	19,051
12 months or longer, Gross unrealized losses	(1,695)	(1,822)
Total, Fair value	171,599	143,039
Total, Gross unrealized losses	(2,333)	(7,198)
Corporate Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	747	5,387
Less than 12 months, Gross unrealized losses	(3)	(76)
12 months or longer, Fair value	2,572	0
12 months or longer, Gross unrealized losses	(10)	0
Total, Fair value	3,319	5,387
Total, Gross unrealized losses	$ (13)	$ (76)