Equity Incentive Plan - Additional Information (Details) (USD $) In Millions, except Share data, unless otherwise specified			1 Months Ended		6 Months Ended		6 Months Ended			1 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jan. 31, 2013 Independent Trustees	Jan. 31, 2012 Independent Trustees	Jun. 30, 2013 Independent Trustees	May 17, 2013 Equity Incentive Plan	Jun. 30, 2013 Equity Incentive Plan Minimum	Jun. 30, 2013 Equity Incentive Plan Maximum	Jun. 30, 2013 2010 Equity Incentive Plan	Jan. 15, 2013 Restricted Stock	Feb. 23, 2012 Restricted Stock	Jun. 30, 2013 Restricted Stock	Jun. 30, 2012 Restricted Stock	Jun. 30, 2013 Restricted Stock	Jun. 30, 2012 Restricted Stock	Jan. 29, 2013 Restricted Stock	Dec. 31, 2012 Restricted Stock	Jun. 30, 2013 Long Term Incentive Plan Units Investment	Jun. 30, 2012 Long Term Incentive Plan Units	Jun. 30, 2013 Long Term Incentive Plan Units Investment	Jun. 30, 2012 Long Term Incentive Plan Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized						3,000,000
Vesting period for share awards under equity							3 years	5 years			3 years
Common share issued as compensation for services performed			22,536	27,592	10,172
Number of trading days preceding the reporting date for which average of closing price of common shares is taken									10 days
Common shares available for issuance									2,400,018
Restricted common Shares granted to executive officers pursuant to the Equity Incentive Plan										17,731	114,567
Time-based awards											61,376					40,829
Performance-based equity, Restricted Share Awards											53,191					40,829
Grant of time-based awards not subject to employment agreements											8,184
Compensation expense valuation of performance-based shares	$ 10.93	$ 10.20
Unrecognized compensation costs												$ 1.7		$ 1.7			$ 1.1
Weighted - average period for recognition of unrecognized compensation costs														1 year 8 months 1 day						1 year 9 months 4 days
Compensation Expense, Recognized												0.2	0.2	0.5	0.4			0.2	0.2	0.4	0.4
Total unrecognized compensation cost related to LTIP Units.	$ 1.4	$ 1.8
LTIP units which has reached parity																		0		0