Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Net increase (decrease) in shareholders' equity resulting from operations
Net Income (Loss) Attributable to Parent	$ 14,862,000	$ 11,727,000	$ 11,600,000	$ 40,335,000	$ 24,786,000	$ 29,537,000	$ 10,768,000	$ 32,055,000	$ 78,524,000		$ 97,146,000		$ 10,327,000
Net Income (Loss) Attributable to Participating Non-controlling Interest									735,000	[1]	0	[1]	0	[1]
Net income (loss) attributable to parent and participating non-controlling interest									79,259,000		97,146,000		10,327,000
Net increase in shareholders' equity resulting from operations– common shares									77,219,000		95,064,000		10,090,000
Net increase in shareholders' equity resulting from operations– LTIP units									1,305,000		2,082,000		237,000
Dividends Paid(2):
Common shareholders									(89,732,000)	[2]	(46,433,000)	[2]	(41,414,000)	[2]
LTIP unit holders									(1,524,000)	[2]	(979,000)	[2]	(968,000)	[2]
Non-controlling Interest									(811,000)	[2]	0	[2]	0	[2]
Total dividends paid to common shareholders, LTIP unit holders, and non-controlling interest									(92,067,000)	[2],[3]	(47,412,000)	[2],[3]	(42,382,000)	[2],[3]
Undistributed (Distributed in excess of) earnings:
Common shareholders									(12,513,000)		48,631,000		(31,324,000)
LTIP Unit holders									(219,000)		1,103,000		(731,000)
Non-controlling interest									(76,000)		0		0
Total undistributed (distributed in excess of) earnings attributable to common shareholders, LTIP unit holders, and non-controlling interest									(12,808,000)		49,734,000		(32,055,000)
Weighted average shares outstanding (basic and diluted):
Weighted average common shares outstanding									23,587,692		17,897,996		16,497,983
Weighted average participating LTIP units									398,789		391,944		385,973
Weighted average non-controlling interest units									212,000		0		0
Basic earnings per common share:
Distributed (in usd per share)									$ 3.83		$ 2.50		$ 2.51
Undistributed (in usd per share)									$ (0.55)		$ 2.81		$ (1.90)
Basic earnings per common share (in usd per share)									$ 3.28		$ 5.31		$ 0.61
Diluted earnings per common share:
Distributed (in usd per share)									$ 3.83		$ 2.50		$ 2.51
Undistributed (in usd per share)									$ (0.55)		$ 2.81		$ (1.90)
Diluted earnings per common share (in usd per share)									$ 3.28		$ 5.31		$ 0.61
Net Income (Loss) Attributable to Non-Participating Non-controlling Interest									$ 100,000

[1] Excludes net increase in equity resulting from operations of $0.1 million attributable to the joint venture partner, which has a non-participating interest as described in Note 7.

[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 years ended December 31, 2013, 2012, and 2011, dividends totaling $3.83, $2.50, and $2.51, respectively, per common share and convertible unit outstanding were declared and paid.