CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Parent	Noncontrolling Interest
Balance at Dec. 31, 2010	$ 587,522	$ 40	$ 303,823	$ (2,857)	$ 17,206	$ 318,212	$ 269,310
Balance (in Shares) at Dec. 31, 2010		40,254,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership (in Shares)		11,000
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership	0	0	49	0	0	49	(49)
Issuance of OP Units to Acquire Real Estate	0
Dividends declared ($0.36 per Common Share)	(15,009)	0	0	0	(14,517)	(14,517)	(492)
Vesting of employee Restricted Share and LTIP awards (in Shares)		95,000
Vesting of employee Restricted Share and LTIP awards	2,223	0	257	0	0	257	1,966
Common Shares issued under Employee Share Purchase Plan (in Shares)		2,000
Common Shares issued under Employee Share Purchase Plan	45	0	45	0	0	45	0
Issuance of LTIP Unit awards to employees	2,441	0	0	0	0	0	2,441
Issuance of Common Shares to trustees (in Shares)		8,000
Issuance of Common Shares to trustees	79	0	79	0	0	79	0
Exercise of Share options (in Shares)		1,000
Exercise of Share options	7	0	7	0	0	7	0
Employee Restricted Shares cancelled (in Shares)		(40,000)
Employee Restricted Shares cancelled	(724)	0	(724)	0	0	(724)	0
Noncontrolling interest distributions	(705)	0	0	0	0	0	(705)
Noncontrolling Interest contributions	43,646	0	0	0	0	0	43,646
Balance before adjustment towards comprehensive income (in Shares)		40,331,000
Balance before adjustment towards comprehensive income	619,525	40	303,536	(2,857)	2,689	303,408	316,117
Comprehensive income (loss):
Net income	34,693	0	0	0	39,657	39,657	(4,964)
Unrealized (loss) on valuation of swap agreements	(1,557)	0	0	(803)	0	(803)	(754)
Reclassification of realized interest on swap agreements	1,637	0	0	1,310	0	1,310	327
Total comprehensive income (loss)	34,773	0	0	507	39,657	40,164	(5,391)
Balance at Jun. 30, 2011	654,298	40	303,536	(2,350)	42,346	343,572	310,726
Balance (in Shares) at Jun. 30, 2011		40,331,000
Balance at Dec. 31, 2011	769,309	43	348,667	(3,913)	39,317	384,114	385,195
Balance (in Shares) at Dec. 31, 2011	42,586,376	42,586,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership (in Shares)		171,000
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership	0	0	2,711	0	0	2,711	(2,711)
Issuance of Common Shares, net of issuance costs (in Shares)		2,901,000
Issuance of Common Shares, net of issuance costs	64,303	3	64,300	0	0	64,303	0
Issuance of OP Units to Acquire Real Estate	2,279	0	0	0	0	0	2,279
Dividends declared ($0.36 per Common Share)	(16,572)	0	0	0	(16,005)	(16,005)	(567)
Vesting of employee Restricted Share and LTIP awards (in Shares)		41,000
Vesting of employee Restricted Share and LTIP awards	1,782	0	89	0	0	89	1,693
Common Shares issued under Employee Share Purchase Plan (in Shares)		1,000
Common Shares issued under Employee Share Purchase Plan	40	0	40	0	0	40	0
Issuance of LTIP Unit awards to employees	2,577	0	0	0	0	0	2,577
Issuance of Common Shares to trustees (in Shares)		0
Issuance of Common Shares to trustees	177	0	177	0	0	177	0
Exercise of Share options (in Shares)		8,000
Exercise of Share options	131	0	131	0	0	131	0
Employee Restricted Shares cancelled (in Shares)		(8,000)
Employee Restricted Shares cancelled	(150)	0	(150)	0	0	(150)	0
Noncontrolling interest distributions	(45,218)	0	0	0	0	0	(45,218)
Balance before adjustment towards comprehensive income (in Shares)		45,700,000
Balance before adjustment towards comprehensive income	886,739	46	415,965	(3,913)	23,312	435,410	451,329
Comprehensive income (loss):
Net income	13,999	0	0	0	10,849	10,849	3,150
Unrealized (loss) on valuation of swap agreements	(2,555)	0	0	(1,494)	0	(1,494)	(1,061)
Reclassification of realized interest on swap agreements	1,283	0	0	923	0	923	360
Total comprehensive income (loss)	12,727	0	0	(571)	10,849	10,278	2,449
Balance at Jun. 30, 2012	899,466	46	415,965	(4,484)	34,161	445,688	453,778
Balance (in Shares) at Jun. 30, 2012	45,703,685	45,700,000
Balance at May. 31, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling Interest contributions	108,081	0	0	0	0	0	108,081
Balance at Jun. 30, 2012	$ 899,466	$ 46	$ 415,965	$ (4,484)	$ 34,161	$ 445,688	$ 453,778
Balance (in Shares) at Jun. 30, 2012	45,703,685	45,700,000