Comprehensive Income - Summary of Amounts Recognized in Other Comprehensive Income Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Available-for-sale securities
Realized gain on sale of securities	$ (58)		$ (525)
Provision for income tax expense	20	67	178	158
Available-for-sale securities, Net of tax	(38)		(347)
Defined benefit pension plan items
Amortization of prior service costs	36	51	108	157
Amortization of actuarial gains/(losses)	10		30
Defined benefit pension plan items, Total before tax	36		108
Defined benefit pension plan items, Provision for income tax expense	(12)		(37)
Defined benefit pension plan items, Net of tax	24		71
Total reclassifications	$ (14)		$ (276)