Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Real estate, accumulated depreciation	$ 112,325	$ 97,392
Deferred financing costs, accumulated amortization	17,080	15,811
Intangible assets, accumulated amortization	3,277	2,976
Indebtedness, fair value	$ 316,620	$ 216,703
Series D cumulative redeemable preferred shares, par value	$ 0.01	$ 0.01
Series D cumulative redeemable preferred shares, shares authorized	4,000,000	4,000,000
Series D cumulative redeemable preferred shares, shares issued	2,600,000	2,600,000
Series D cumulative redeemable preferred shares, shares outstanding	2,600,000	2,600,000
Preferred shares, Authorized	25,000,000	25,000,000
Common shares, par value	$ 0.03	$ 0.03
Common shares, shares authorized	200,000,000	200,000,000
Common shares, shares issued	69,960,454	58,913,142
Common shares, shares outstanding	69,960,454	58,913,142
Unvested restricted common share awards	391,268
7.75% Series A cumulative redeemable preferred shares
Preferred shares, Authorized	4,760,000	4,760,000
Preferred shares, dividend rate	7.75%	7.75%
Cumulative redeemable preferred shares, liquidation preference	$ 25.00	$ 25.00
Cumulative redeemable preferred shares, shares issued	3,749,288	3,124,288
Cumulative redeemable preferred shares, shares outstanding	3,749,288	3,124,288
Preferred Shares, par value	$ 0.01	$ 0.01
8.375% Series B cumulative redeemable preferred shares
Preferred shares, Authorized	4,300,000	4,300,000
Preferred shares, dividend rate	8.375%	8.375%
Cumulative redeemable preferred shares, liquidation preference	$ 25.00	$ 25.00
Cumulative redeemable preferred shares, shares issued	2,288,465	2,288,465
Cumulative redeemable preferred shares, shares outstanding	2,288,465	2,288,465
Preferred Shares, par value	$ 0.01	$ 0.01
8.875% Series C cumulative redeemable preferred shares
Preferred shares, Authorized	3,600,000	3,600,000
Preferred shares, dividend rate	8.875%	8.875%
Cumulative redeemable preferred shares, liquidation preference	$ 25.00	$ 25.00
Cumulative redeemable preferred shares, shares issued	1,640,100	1,640,100
Cumulative redeemable preferred shares, shares outstanding	1,640,100	1,640,100
Preferred Shares, par value	$ 0.01	$ 0.01
Series E cumulative redeemable preferred shares
Preferred shares, Authorized	4,000,000	4,000,000
Preferred Shares, par value	$ 0.01	$ 0.01