Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Net increase (decrease) in shareholders' equity resulting from operations
Net Income (Loss) Attributable to Parent		$ 3,896	$ 12,948	[1]	$ 36,309		$ 56,530	[1]
Net Income (Loss) Attributable to Participating Non-controlling Interest	[2]	25	98		227		456
Net income (loss) attributable to parent and participating non-controlling interest		3,921	13,046		36,536		56,986
Net increase in shareholders' equity resulting from operations– common shares		3,847	12,756		35,849		55,653
Net increase in shareholders' equity resulting from operations– LTIP units		49	192		460		877
Dividends Paid(2):
Common shareholders	[3]	(21,727)	(19,590)		(65,211)		(58,934)
LTIP unit holders	[3]	(279)	(317)		(837)		(950)
Non-controlling Interest	[3]	(138)	(163)		(414)		(326)
Total dividends paid to common shareholders, LTIP unit holders, and non-controlling interest	[3]	(22,144)	(20,070)		(66,462)	[4]	(60,210)	[4]
Undistributed (Distributed in excess of) earnings:
Common shareholders		(17,880)	(6,834)		(29,362)		(3,281)
LTIP unit holders		(230)	(125)		(377)		(73)
Non-controlling interest		(113)	(65)		(187)		130
Total undistributed (distributed in excess of) earnings attributable to common shareholders, LTIP unit holders, and non-controlling interest		$ (18,223)	$ (7,024)		$ (29,926)		$ (3,224)
Weighted average shares outstanding (basic and diluted):
Weighted average common shares outstanding		33,438,047	27,442,146		33,445,758		26,113,839
Weighted average participating LTIP units		430,267	411,926		429,635		411,346
Weighted average non-controlling interest units		212,000	212,000		212,000		212,000
Basic earnings per common share:
Distributed (in usd per share)		$ 0.65	$ 0.77		$ 1.95		$ 2.31
Undistributed (Distributed in excess of) (in usd per share)		(0.53)	(0.31)		(0.88)		(0.18)
Basic earnings per common share (in usd per share)		0.12	0.46		1.07		2.13
Diluted earnings per common share:
Distributed (in usd per share)		0.65	0.77		1.95		2.31
Undistributed (Distributed in excess of) (in usd per share)		(0.53)	(0.31)		(0.88)		(0.18)
Diluted earnings per common share (in usd per share)		$ 0.12	$ 0.46		$ 1.07		$ 2.13
Net Income (Loss) Attributable to Non-Participating Non-controlling Interest		$ 6	$ 100		$ 32		$ 200

[1] Conformed to current period presentation.

[2] For the three month periods ended September 30, 2015 and 2014, excludes net increase (decrease) in equity resulting from operations of $6 thousand and $0.1 million, respectively attributable to joint venture partners, which have non-participating interests as described in Note 9. For the nine month periods ended September 30, 2015 and 2014, excludes net increase in equity resulting from operations of $32 thousand and $0.2 million, respectively attributable to joint venture partners, which have non-participating interests as described in Note 9.

[3] 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.

[4] For the nine month periods ended September 30, 2015 and 2014, dividends totaling $1.95 and $2.31, respectively, per common share and convertible unit outstanding, were declared and paid.