Condensed Financial Information (Parent Company Only) (Details 3) (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
Operating Activities
Net income	$ 5,170	$ 4,850	$ 4,910	$ 4,613	$ 3,522	$ 3,417	$ 3,093	$ 2,765	$ 19,543	$ 12,797	$ 10,455
Items not requiring (providing) cash
Share based compensation									33	35	30
Other assets									1,030	286	183
Other liabilities									(3,072)	971	2,057
Net cash provided by operating activities									26,346	22,412	24,910
Investing Activities
Acquisition of Heartland									26,283
Net cash used in by investing activities									(60,383)	(142,173)	27,815
Financing Activities
Redemption of preferred stock										(18,750)	(6,250)
Issuance of preferred stock										12,500
Dividends paid on preferred shares									(481)	(792)	(1,245)
Dividends paid on common shares									(3,047)	(2,325)	(2,240)
Net cash used in financing activities									44,325	124,525	(105,744)
Net Change in Cash and Cash Equivalent									10,288	4,764	(53,019)
Cash and Cash Equivalents, Beginning of Period				20,447				15,683	20,447	15,683	68,702
Cash and Cash Equivalents, End of Period	30,735				20,447				30,735	20,447	15,683
Parent Company [Member]
Operating Activities
Net income									19,543	12,797	10,455
Items not requiring (providing) cash
Equity in undistributed net income of Bank Change in									(4,766)	(4,288)	(6,759)
Income taxes receivable									(137)	(236)	33
Dividends receivable from Bank									(16,500)	(10,000)	(5,000)
Share based compensation									33	35	30
Amortization of unearned compensation									187	100	68
Issuance of restricted shares									115	60	34
Other assets									(176)	473	(308)
Other liabilities									1,128	129	250
Net cash provided by operating activities									15,927	9,070	6,303
Investing Activities
Investment in Bank											(3,500)
Purchases and assumption of ATSB											3,412
Acquisition of Heartland									(7,248)
Net cash used in by investing activities									(7,248)		(88)
Financing Activities
Redemption of preferred stock										(18,750)	(6,250)
Issuance of preferred stock										12,500
Dividends paid on preferred shares									(481)	(792)	(1,245)
Dividends paid on common shares									(3,047)	(2,325)	(2,240)
Exercise of stock options									226	63	197
Net cash used in financing activities									(3,302)	(9,304)	(9,538)
Net Change in Cash and Cash Equivalent									5,377	(234)	(3,323)
Cash and Cash Equivalents, Beginning of Period				8,262				8,496	8,262	8,496	11,819
Cash and Cash Equivalents, End of Period	$ 13,639				$ 8,262				$ 13,639	$ 8,262	$ 8,496