Common Share Capitalization (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		14 Months Ended		0 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Dec. 31, 2011	Aug. 20, 2012 Secondary Offering Public [Member]	Sep. 12, 2012 Secondary Offering Overallotment Option [Member]
Common Stock Capitalization [Line Items]
Common stock, shares issued	20,483,696		20,483,696		20,483,696	16,447,651	3,500,000	525,000
Net proceeds from issuance of shares							$ 76,700,000	$ 11,100,000
Overallotment option percentage by underwriters								15.00%
Aggregate cost of shares repurchase					10,000,000
Shares repurchased under share repurchase program	0	17,500	0	17,500	60,980
Aggregate cost of shares repurchased	0	309,000	0	309,000	1,100,000
Average price per share repurchased					$ 17.22
Dividend Per Share	$ 0.70	$ 0.40	$ 1.80	$ 2.11
Dividend Amount	$ 14,200,000	$ 6,800,000	$ 32,800,000	$ 35,600,000