Consolidated Statements Of Cash Flows (USD $)	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net income	$ 49,980,000	$ 54,331,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	41,917,000	36,856,000
In-place lease adjustment	421,000	98,000
Tenant improvement reimbursements net of lease incentives	(432,000)	(265,000)
Amortization of mortgage premium	(118,000)	(140,000)
Gain on sale of real estate facility		(5,153,000)
Stock compensation	822,000	1,135,000
Decrease in receivables and other assets	1,413,000	587,000
Increase (decrease) in accrued and other liabilities	(1,945,000)	1,467,000
Total adjustments	42,078,000	34,585,000
Net cash provided by operating activities	92,058,000	88,916,000
Cash flows from investing activities:
Capital improvements to real estate facilities	(17,561,000)	(17,709,000)
Acquisition of real estate facilities	(26,613,000)	(123,582,000)
Proceeds from sale of real estate facility		9,181,000
Net cash used in investing activities	(44,174,000)	(132,110,000)
Cash flows from financing activities:
Borrowings on credit facility	17,500,000
Borrowings on note payable to affiliate	121,000,000
Repayment of borrowings on credit facility	(93,000,000)
Repayment of borrowings on note payable to affiliate	(5,000,000)
Principal payments on mortgage notes payable	(549,000)	(540,000)
Repayment of mortgage note payable	(2,660,000)
Proceeds from the exercise of stock options	1,050,000	5,896,000
Redemption/repurchase of preferred units	(39,087,000)	(20,000,000)
Redemption of preferred stock		(54,125,000)
Distributions paid to common shareholders	(21,742,000)	(21,566,000)
Distributions paid to preferred shareholders	(20,899,000)	(22,024,000)
Distributions paid to noncontrolling interests -- common units	(6,428,000)	(6,428,000)
Distributions paid to noncontrolling interests - preferred units	(199,000)	(2,552,000)
Net cash used in financing activities	(50,014,000)	(121,339,000)
Net decrease in cash and cash equivalents	(2,130,000)	(164,533,000)
Cash and cash equivalents at the beginning of the period	5,066,000	208,229,000
Cash and cash equivalents at the end of the period	2,936,000	43,696,000
Adjustment to noncontrolling interests in underlying operating partnership:
Noncontrolling interests - common units	9,122,000	904,000
Paid-in capital	(9,122,000)	(904,000)
Gain on repurchase of preferred equity:
Preferred units	(8,748,000)
Paid-in capital	8,748,000
Issuance costs related to the redemption/repurchase of preferred equity:
Cumulative distributions		(1,854,000)
Noncontrolling interest - common units	(1,359,000)	(582,000)
Paid-in capital	$ 1,359,000	$ 2,436,000