Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015
Net increase (decrease) in shareholders' equity resulting from operations
Net Income (Loss) Attributable to Parent		$ 516	$ 3,896	$ (17,699)		$ 36,309
Net Income (Loss) Attributable to Participating Non-controlling Interest	[1]	3	25	(112)		227
Net income (loss) attributable to parent and participating non-controlling interest		519	3,921	(17,811)		36,536
Net increase (decrease) in shareholders' equity resulting from operations– common shares		509	3,847	(17,460)		35,849
Net increase (decrease) in shareholders' equity resulting from operations– LTIP units		7	49	(239)		460
Dividends Paid:
Common shareholders	[2]	(16,309)	(21,727)	(49,263)		(65,211)
LTIP unit holders	[2]	(225)	(279)	(675)		(837)
Non-controlling Interest	[2]	(106)	(138)	(318)		(414)
Total dividends paid to common shareholders, LTIP unit holders, and non-controlling interest	[2]	(16,640)	(22,144)	(50,256)	[3]	(66,462)	[3]
Undistributed (Distributed in excess of) earnings:
Common shareholders		(15,800)	(17,880)	(66,723)		(29,362)
LTIP unit holders		(218)	(230)	(914)		(377)
Non-controlling interest		(103)	(113)	(430)		(187)
Total undistributed (distributed in excess of) earnings attributable to common shareholders, LTIP unit holders, and non-controlling interest		$ (16,121)	$ (18,223)	$ (68,067)		$ (29,926)
Weighted average shares outstanding (basic and diluted):
Weighted average common shares outstanding		32,643,154	33,438,047	32,854,979		33,445,758
Weighted average participating LTIP units		451,125	430,267	450,336		429,635
Weighted average non-controlling interest units		212,000	212,000	212,000		212,000
Basic earnings per common share:
Distributed (in usd per share)		$ 0.50	$ 0.65	$ 1.50		$ 1.95
Undistributed (Distributed in excess of) (in usd per share)		(0.48)	(0.53)	(2.03)		(0.88)
Basic earnings per common share (in usd per share)		0.02	0.12	(0.53)		1.07
Diluted earnings per common share:
Distributed (in usd per share)		0.50	0.65	1.50		1.95
Undistributed (Distributed in excess of) (in usd per share)		(0.48)	(0.53)	(2.03)		(0.88)
Diluted earnings per common share (in usd per share)		$ 0.02	$ 0.12	$ (0.53)		$ 1.07
Net Income (Loss) Attributable to Non-Participating Non-controlling Interest		$ 31	$ 6	$ 200		$ 32

[1] For the three month periods ended September 30, 2016 and 2015, excludes net increase in equity resulting from operations of $31 thousand and $6 thousand, respectively attributable to joint venture partners, which have non-participating interests as described in Note 9. For the nine month periods ended September 30, 2016 and 2015, excludes net increase in equity resulting from operations of $0.2 million and $32 thousand, respectively attributable to joint venture partners, which have non-participating interests as described in Note 9.

[2] The Company pays quarterly dividends in arrears, so a portion of the dividends paid in each calendar year relate to the prior year's earnings.

[3] For the nine month periods ended September 30, 2016 and 2015, dividends totaling $1.50 and $1.95, respectively, per common share and convertible unit outstanding, were declared and paid.