CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Parent	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Noncontrolling Interest
Balance at Dec. 31, 2012	$ 1,070,256	$ 622,797	$ 52	$ 581,925	$ (4,307)	$ 45,127	$ 447,459
Balance (in Shares) at Dec. 31, 2012	52,482,598		52,482,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership (in Shares)			92,000
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership	0	1,548	0	1,548	0	0	(1,548)
Issuance of Common Shares, net of issuance costs (in Shares)			2,822,000
Issuance of Common Shares, net of issuance costs	75,871	75,871	3	75,868	0	0	0
Issuance of OP Units to Acquire Real Estate	0
Dividends declared	(23,734)	(23,053)	0	0	0	(23,053)	(681)
Vesting of employee Restricted Share and LTIP awards (in Shares)			29,000
Vesting of employee Restricted Share and LTIP awards	2,580	120	0	120	0	0	2,460
Common Shares issued under Employee Share Purchase Plan (in Shares)			2,000
Common Shares issued under Employee Share Purchase Plan	40	40	0	40	0	0	0
Issuance of Common Shares to trustees (in Shares)			0
Issuance of Common Shares to trustees	206	206	0	206	0	0	0
Exercise of Share options (in Shares)			21,000
Exercise of Share options	370	370	0	370	0	0	0
Employee Restricted Shares cancelled (in Shares)			(3,000)
Employee Restricted Shares cancelled	(83)	(83)	0	(83)	0	0	0
Acquisition Of Interest In Unconsolidated Affiliate Investment In Unconsolidated Affiliates	(33,949)	0	0	0	0	0	(33,949)
Noncontrolling interest distributions	(18,471)	0	0	0	0	0	(18,471)
Noncontrolling Interest, Increase from Contributions	15,567	0	0	0	0	0	15,567
Balance before adjustment towards comprehensive income (in Shares)			55,445,000
Balance before adjustment towards comprehensive income	1,088,653	677,816	55	659,994	(4,307)	22,074	410,837
Comprehensive (loss) income:
Net income	20,793	18,380	0	0	0	18,380	2,413
Unrealized income (loss) on valuation of swap agreements	3,104	2,707	0	0	2,707	0	397
Reclassification of realized interest on swap agreements	1,337	845	0	0	845	0	492
Total comprehensive (loss) income	25,234	21,932	0	0	3,552	18,380	3,302
Balance at Jun. 30, 2013	$ 1,113,887	$ 699,748	$ 55	$ 659,994	$ (755)	$ 40,454	$ 414,139
Balance (in Shares) at Jun. 30, 2013	55,444,779		55,445,000