Intangible Assets and Liabilities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($) property	Dec. 31, 2014 USD ($) property
Intangible Assets And Liabilities [Line Items]
Number of income properties acquired | property	10	4	4
Net increase in intangible assets and liabilities	$ 16,100,000
Amortization expense of intangible assets and liabilities	456,000	$ 1,500,000	$ 768,000
Depreciation and amortization
Intangible Assets And Liabilities [Line Items]
Amortization expense of intangible assets and liabilities	2,700,000	1,700,000
Income properties revenue
Intangible Assets And Liabilities [Line Items]
Amortization expense of intangible assets and liabilities	(2,200,000)	(200,000)
Value of In-Place Leases [Member]
Intangible Assets And Liabilities [Line Items]
Increase in sub total intangible lease assets	$ 14,900,000
Number of income properties acquired | property	10
Value of Above Market In-Place Leases
Intangible Assets And Liabilities [Line Items]
Increase in sub total intangible lease assets	$ 1,700,000
Value of Intangible Leasing Costs [Member]
Intangible Assets And Liabilities [Line Items]
Increase in sub total intangible lease assets	3,300,000
Value of Below Market In-Place Leases
Intangible Assets And Liabilities [Line Items]
Increase (decrease) in below market value	1,100,000
Value of Below Market In-Place Leases | Wells Fargo | Raleigh, North Carolina
Intangible Assets And Liabilities [Line Items]
Increase (decrease) in below market value	$ 29,000,000	$ 31,600,000
2016 Disposals | Sold
Intangible Assets And Liabilities [Line Items]
Number of disposed properties | property	19
2015 Disposals | Sold
Intangible Assets And Liabilities [Line Items]
Increase (decrease) in below market value	$ (2,400,000)
Number of disposed properties | property	19	6
2014 Disposals | Sold
Intangible Assets And Liabilities [Line Items]
Number of disposed properties | property			1