Earnings per share of the Trust (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	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
Earnings Per Share Disclosure
Income from continuing operations									$ 37,277	$ 61,204	$ 28,702
Income from continuing operations attributable to noncontrolling interests									1,131	2,414	1,267
Income from discontinued operations attributable to noncontrolling interest									2,867	2,188	1,143
Income from discontinued operations									82,002	48,621	22,529
Parent Company [Member]
Earnings Per Share Disclosure
Weighted average common shares, basic									50,677
Weighted average partnership units outstanding									2,351
Effect of dilutive securities (shares)									88
Weighted average common shares - diluted									53,116
Income from continuing operations									37,277	61,204	28,702
Income from continuing operations attributable to noncontrolling interests									1,131
Income from continuing operations allocated to unvested restricted shares									34
Income from continuing operations available for common shareholders, adjusted									36,112	58,737	27,413
Income from discontinued operations attributable to noncontrolling interest									2,867
Income from discontinued operations allocated to unvested restricted shares									74
Income from discontinued operations available for common shareholders, adjusted									79,061
Earnings per share - basic	$ (0.12)	$ 1.04	$ 1.38	$ 0.50	$ 0.53	$ 0.74	$ 0.69	$ 0.60	$ 2.27	$ 2.56	$ 1.32
Income from discontinued operations									$ 82,002	$ 48,621	$ 22,529	[1]
Earnings per unit - diluted	$ (0.12)	$ 1.04	$ 1.37	$ 0.50	$ 0.53	$ 0.74	$ 0.69	$ 0.60	$ 2.25	$ 2.56	$ 1.31

[1] The 2011 column shows the segment break down based on the 2012 same store portfolios. A comparison using the 2013 same store portfolio would not be comparative due to the nature of the classifications.