Consolidated Statements Of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 69,664,000	$ 55,451,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	53,258,000	56,736,000
In-place lease adjustment	(663,000)	(441,000)
Tenant improvement reimbursements net of lease incentives	(940,000)	(839,000)
Gain on sale of real estate facilities	(12,487,000)
Stock compensation	5,037,000	3,898,000
Decrease (increase) in receivables and other assets	(2,954,000)	4,664,000
Increase (decrease) in accrued and other liabilities	530,000	(2,959,000)
Total adjustments	41,781,000	61,059,000
Net cash provided by operating activities	111,445,000	116,510,000
Cash flows from investing activities:
Capital expenditures to real estate facilities	(23,865,000)	(22,250,000)
Capital expenditures to land and building held for development	(1,846,000)	(1,219,000)
Proceeds from sale of real estate facilities	24,490,000
Net cash used in investing activities	(1,221,000)	(23,469,000)
Cash flows from financing activities:
Proceeds from the exercise of stock options	2,000,000	2,443,000
Distributions paid to preferred shareholders	(30,244,000)	(30,244,000)
Distributions paid to noncontrolling interests — common units	(7,305,000)	(7,305,000)
Distributions paid to common shareholders	(26,948,000)	(26,893,000)
Net cash used in financing activities	(62,497,000)	(61,999,000)
Net increase in cash and cash equivalents	47,727,000	31,042,000
Cash and cash equivalents at the beginning of the period	152,467,000	31,481,000
Cash and cash equivalents at the end of the period	200,194,000	62,523,000
Adjustment to noncontrolling interests in underlying operating partnership:
Noncontrolling interests - common units	1,055,000	984,000
Paid-in capital	$ (1,055,000)	$ (984,000)