Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity (Details)

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Shareholders' Equity (Details) (USD $)
3 Months Ended 12 Months Ended
Mar. 31, 2011
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Shareholders' Equity [Abstract]        
Maximum offering price under ATM program   $ 100,000,000    
Aggregate Number of Shares Sold 1,516,379 0    
Aggregate Gross Proceeds 49,575,000      
Aggregate Net Proceeds   $ 48,400,000 $ 0 $ 0
Average Sales Price Per Share $ 32.69      
Stock issuance program, expiry date   February 2, 2012