Comprehensive Income Reported in Consolidated Statements of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Comprehensive Income (Loss) [Line Items]
Unrealized holding gains (losses) on available-for-sale securities during the period, net of tax	$ 1,313	$ (103)	$ 2,450	$ 1,035
Unrealized gain on derivative carried at fair value during the period, net of tax	24	51	48	34
Accumulated Other Comprehensive Income(Loss) beginning of period	1,723	544	562	(577)
Accumulated Other Comprehensive Income, end of period	$ 3,060	$ 492	$ 3,060	$ 492