Segment Reporting Narrative (Details) - building	3 Months Ended
	Mar. 31, 2018	May 02, 2016
Segment Reporting Information [Line Items]
Number of buildings	4
Number of buildings with one tenant	2
One Tenant Lease
Segment Reporting Information [Line Items]
Lease term	20 years
Subsidiary Lease
Segment Reporting Information [Line Items]
Lease term	130 months
Great Park Venture
Segment Reporting Information [Line Items]
Percentage of equity ownership	37.50%	37.50%
Gateway Commercial Venture
Segment Reporting Information [Line Items]
Percentage of equity ownership	75.00%