Parent Company Only Financial Statements Condensed statements of cash flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Net income	$ 14,025	$ 11,372	$ 8,761
Depreciation, amortization and accretion, net	5,403	5,398	3,938
(Increase) decrease in other assets	912	1,900	5,955
Increase (decrease) in other liabilities	1,087	2,061	(4,074)
Net cash provided by operating activities	22,889	18,976	7,508
Repayment of short-term debt	(8,250)	0	0
Proceeds from short-term debt	0	8,250	0
Proceeds from issuance of common stock	1,255	406	971
Purchase of treasury stock	3,912	2,385	2,499
Dividends paid on preferred stock	(3,788)	(2,990)	(2,136)
Dividends paid on common stock	(2,843)	(1,697)	(1,714)
Net cash provided by financing activities	60,397	14,081	33,038
Increase (decrease) in cash	9,610	(158,391)	141,082
Cash and cash equivalents at beginning of period	73,102	231,493	90,411
Cash and cash equivalents at end of period	82,712	73,102	231,493
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	14,025	11,372	8,761
Depreciation, amortization and accretion, net	114	71	47
Dividends from subsidiaries	1,438	938	6,744
Equity in undistributed earnings of subsidiaries	(14,052)	(11,803)	(3,675)
(Increase) decrease in other assets	(1,436)	(3,283)	(9,966)
Increase (decrease) in other liabilities	319	128	(12)
Net cash provided by operating activities	408	(2,577)	1,899
Repayment of short-term debt	(8,250)	0	0
Proceeds from short-term debt	0	8,250	0
Proceeds from issuance of preferred stock	8,250	19,150	0
Proceeds from issuance of common stock	1,255	406	971
Purchase of treasury stock	(3,912)	(2,385)	(2,499)
Dividends paid on preferred stock	(3,788)	(2,990)	(2,136)
Dividends paid on common stock	(2,843)	(1,697)	(1,714)
Net cash provided by financing activities	(9,288)	20,734	(5,378)
Increase (decrease) in cash	(8,880)	18,157	(3,479)
Cash and cash equivalents at beginning of period	20,538	2,381	5,860
Cash and cash equivalents at end of period	$ 11,658	$ 20,538	$ 2,381