Summary of Significant Accounting Policies Earnings Per Share Calculation (Details) (USD $) In Thousands, except Share data, 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
Summary of Significant Accounting Policies [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic									$ 13,602	$ 11,262	$ 9,760
Net Income (Loss) Available to Common Stockholders, Diluted									$ 13,602	$ 11,262	$ 9,760
Weighted Average Number of Shares Outstanding, Basic									8,763,000	8,610,000	8,532,000
Weighted Average Number Diluted Shares Outstanding Adjustment									137,000	110,000	101,000
Diluted (in shares)									8,900,000	8,720,000	8,633,000
Basic (in dollars per share)	$ 0.16	$ 0.69	$ 0.48	$ 0.22	$ 0.21	$ 0.43	$ 0.41	$ 0.26	$ 1.55	$ 1.31	$ 1.14
Incremental Common Shares Attributal To Share Based Payements Arrangements									$ 0.02	$ 0.02	$ 0.01
Diluted (in dollars per share)	$ 0.16	$ 0.67	$ 0.47	$ 0.22	$ 210.00	$ 0.42	$ 0.40	$ 0.26	$ 1.53	$ 1.29	$ 1.13