Accumulated Other Comprehensive Income - Reconciliation of Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Equity [Abstract]
Unrealized gains (losses) arising during the period, Pre- tax amount	$ (2,744)	$ 629	$ (3,220)	$ 785
Reclassification adjustment for gains recognized in net income, Pre-Tax Amount	(24)	(61)	(125)	(108)
Net unrealized gains (losses), Pre-Tax Amount	(2,768)	568	(3,345)	677
Other comprehensive income, Pre-Tax Amount	(2,768)	568	(3,345)	677
Unrealized gains (losses) arising during the period, Tax (Expense) Benefit	933	(214)	1,095	(267)
Reclassification adjustment for gains recognized in net income, Tax (Expense) Benefit	8	21	42	37
Net unrealized gains (losses), Tax (Expense) Benefit	941	(193)	1,137	(230)
Other comprehensive income, Tax (Expense) Benefit	941	(193)	1,137	(230)
Unrealized gains (losses) on securities, net of reclassification adjustment	(1,811)	415	(2,125)	518
Reclassification adjustment for gains recognized in net income, Net-of-Tax Amount	(16)	(40)	(83)	(71)
Net unrealized gains (losses), net of tax amount	(1,827)	375	(2,208)	447
Other comprehensive income, Net-of-Tax Amount	$ (1,827)	$ 375	$ (2,208)	$ 447