Segment Information - Segment Schedules (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	3
Segment Reporting Information [Line Items]
Real estate rental revenue	$ 83,174	$ 84,881
Real estate expenses	29,210	29,901
Net operating income	53,964	54,980
Depreciation and amortization	(29,547)	(29,969)
General and administrative expenses	(7,429)	(5,821)
Lease origination expenses	(378)	0
Interest expense	(12,641)	(12,827)
Real estate impairment	(8,374)	(1,886)
Loss on extinguishment of debt	0	(1,178)
Net (loss) income	(4,405)	3,299
Less: Net income attributable to noncontrolling interests in subsidiaries	0	0
Net loss attributable to the controlling interests	(4,405)	3,299
Capital expenditures	7,348	8,017
Total assets	2,408,467	2,518,295	$ 2,417,104
Office
Segment Reporting Information [Line Items]
Real estate rental revenue	42,293	45,547
Real estate expenses	15,224	16,302
Net operating income	27,069	29,245
Capital expenditures	4,923	4,945
Total assets	1,238,795	1,361,880
Retail
Segment Reporting Information [Line Items]
Real estate rental revenue	16,546	15,671
Real estate expenses	4,516	4,160
Net operating income	12,030	11,511
Capital expenditures	555	475
Total assets	336,229	344,904
Multifamily
Segment Reporting Information [Line Items]
Real estate rental revenue	24,335	23,663
Real estate expenses	9,470	9,439
Net operating income	14,865	14,224
Capital expenditures	1,803	2,425
Total assets	796,525	769,643
Corporate and Other
Segment Reporting Information [Line Items]
Real estate rental revenue	0	0
Real estate expenses	0	0
Net operating income	0	0
Capital expenditures	67	172
Total assets	$ 36,918	$ 41,868