Reclassification Adjustments Out of Accumulated 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
Comprehensive Income [Line Items]
Investment securities gains	$ 62	$ 90	$ 118		$ 163
Income before taxes			118		163
Tax expense			47		65
Net income			71		98
Recognized actuarial loss 1	(563)	(349)	(927)	[1]	(699)	[1]
Income before taxes			927		699
Tax expense			370		279
Net income			$ 557		$ 420

[1] This amount is included in the computation of net periodic pension cost, see Note 10