Consolidated Statements Of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income	$ 95,948,000	$ 173,884,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization expense	49,643,000	48,298,000
Tenant improvement reimbursement amortization, net of lease incentive amortization	(663,000)	(1,134,000)
Gain on sale of real estate facilities		(85,283,000)
Stock compensation expense	1,889,000	1,781,000
Amortization of financing costs	272,000	263,000
Other, net	(5,920,000)	(6,055,000)
Total adjustments	45,221,000	(42,130,000)
Net cash provided by operating activities	141,169,000	131,754,000
Cash flows from investing activities
Capital expenditures to real estate facilities	(17,503,000)	(15,083,000)
Capital expenditures to land and building held for development	(993,000)	(403,000)
Acquisition of real estate facility	(13,736,000)	(142,399,000)
Consolidation of joint venture		1,082,000
Proceeds from sale of real estate facilities		126,836,000
Net cash used in investing activities	(32,232,000)	(29,967,000)
Cash flows from financing activities
Borrowings on credit facility		50,000,000
Repayment of borrowings on credit facility		(40,000,000)
Payment of financing costs	(157,000)	(148,000)
Proceeds from the exercise of stock options	709,000	1,228,000
Redemption of preferred stock		(130,000,000)
Cash paid for taxes in lieu of shares upon vesting of restricted stock units	(5,500,000)	(4,529,000)
Cash paid to restricted stock unit holders	(480,000)	(536,000)
Distributions paid to preferred shareholders	(25,918,000)	(26,655,000)
Distributions paid to common shareholders	(57,538,000)	(46,396,000)
Distributions paid to noncontrolling interests - common units	(15,341,000)	(12,419,000)
Distributions paid to noncontrolling interests - joint venture	(45,000)	0
Net cash used in financing activities	(104,270,000)	(209,455,000)
Net increase (decrease) in cash and cash equivalents	4,667,000	(107,668,000)
Cash, cash equivalents and restricted cash at the beginning of the period	38,467,000	115,970,000
Cash, cash equivalents and restricted cash at the end of the period	43,134,000	8,302,000
Adjustment to noncontrolling interests- common units in the OP
Noncontrolling interests- common units	(1,028,000)	(606,000)
Paid-in capital	$ 1,028,000	606,000
Consolidation of joint venture
Land		21,814,000
Buildings and improvements		85,436,000
Other, net		(2,320,000)
Investment in and advances to unconsolidated joint venture		(100,898,000)
Noncontrolling interest - joint venture		$ (4,032,000)