Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statements of Comprehensive Income [Abstract]
Net Income	$ 5,170	$ 4,850	$ 4,910	$ 4,613	$ 3,522	$ 3,417	$ 3,093	$ 2,765	$ 19,543	$ 12,797	$ 10,455
Other Comprehensive Income (Loss)
Change in fair value of derivative instruments, net of taxes of $(203) for 2012, $(1,239) for 2011 and $(631) for 2010, respectively									(376)	(2,300)	(1,172)
Unrealized appreciation (depreciation) on available-for-sale securities, net of taxes of $881 for 2012, $4,819 for 2011 and $(998) for 2010, respectively									1,636	8,949	(1,853)
Less: reclassification adjustment for realized gains included in net income, net of taxes of $1 for 2012, $622 for 2011 and $187 for 2010, respectively									1	1,155	346
Other Comprehensive Income									1,259	5,494	(3,371)
Comprehensive Income									$ 20,802	$ 18,291	$ 7,084