Retained Earnings Retained Earnings Rollforward (Details) (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	Dec. 31, 2009
Retained Earnings [Line Items]
Retained Earnings (Accumulated Deficit)	$ 51,804				$ 46,669				$ 51,804	$ 46,669	$ 43,603	$ 41,785
Net Income	1,593	5,974	4,163	1,910	1,828	3,734	3,470	2,268	13,640	11,300	9,798
Retained Earnings before Dividends									60,309	54,903	51,583
Preferred Stock Dividend Requirement									38	38	38
Dividends, Common Stock									8,467	8,196	7,942
Dividends									8,505	8,234	7,980
Cumulative Preferred Stock
Retained Earnings [Line Items]
Preferred Stock Dividend Requirement									26	26	26
Series A Voting
Retained Earnings [Line Items]
Preferred Stock Dividend Requirement									$ 12	$ 12	$ 12