Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Unrealized gains on securities available-for-sale
Unrealized holding gains arising during the year, income tax expense	$ 1,872	$ 143	$ 1,076
Reclassification adjustment for gain on liquidation of equity security included in securities available-for-sale, income tax expense	34	1
Reclassification adjustment of impairment loss on security available for sale , income tax benefit			$ 61