CONSOLIDATED STATEMENTS OF INCOME - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
REVENUES:
Rental income	$ 667,360,000	$ 628,883,000	$ 590,161,000
Tenant reimbursement income	56,950,000	52,418,000	44,943,000
Fee and other income	34,651,000	37,666,000	48,237,000
Total revenues	758,961,000	718,967,000	683,341,000
EXPENSES:
Operating	274,078,000	266,136,000	250,040,000
Depreciation and amortization	258,225,000	266,037,000	269,450,000
General and administrative	57,563,000	61,577,000	53,510,000
Transaction related costs	1,471,000	2,027,000	2,404,000
Real estate impairment loss	46,000,000
Total expenses	637,337,000	595,777,000	575,404,000
Operating income	121,624,000	123,190,000	107,937,000
Income from unconsolidated joint ventures	3,468,000	20,185,000	7,413,000
Loss from unconsolidated real estate funds	(269,000)	(6,143,000)	(498,000)
Interest and other income (loss), net	8,117,000	(9,031,000)	6,934,000
Interest and debt expense	(147,653,000)	(143,762,000)	(153,138,000)
Loss on early extinguishment of debt		(7,877,000)	(4,608,000)
Gain on sale of real estate	36,845,000	133,989,000
Unrealized gain on interest rate swaps		1,802,000	39,814,000
Net income before income taxes	22,132,000	112,353,000	3,854,000
Income tax expense	(3,139,000)	(5,177,000)	(1,785,000)
Net income	18,993,000	107,176,000	2,069,000
Less net (income) loss attributable to noncontrolling interests in:
Consolidated joint ventures	(8,182,000)	10,365,000	(15,423,000)
Consolidated real estate fund	(720,000)	(19,797,000)	1,316,000
Operating Partnership	(944,000)	(11,363,000)	2,104,000
Net income (loss) attributable to common stockholders	$ 9,147,000	$ 86,381,000	$ (9,934,000)
INCOME (LOSS) PER COMMON SHARE - BASIC:
Income (loss) per common share	$ 0.04	$ 0.37	$ (0.05)
Weighted average shares outstanding	239,526,694	236,372,801	218,053,062
INCOME (LOSS) PER COMMON SHARE - DILUTED:
Income (loss) per common share	$ 0.04	$ 0.37	$ (0.05)
Weighted average shares outstanding	239,555,636	236,401,548	218,053,062