Investment in Unconsolidated Joint Ventures (Charlotte Gateway Village, LLC) (Details) - Charlotte Gateway Village, LLC ft² in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Ownership percentage of partner in joint venture	50.00%
Square footage of real estate property (square feet) | ft²	1.1
Compounded rate of return received by Company (percent)		11.46%
Percentage of Company's income (loss) received in final step of distribution		0.5
Allocation of net income and cash flows, percentage	50.00%
Maximum internal rate of return to be achieved	17.00%
Allocation of proceeds from capital transactions, percentage, third priority	20.00%
Maximum IRR on project (percent)	17.00%
Cash balance of joint venture | $	$ 12.1
BOA
Schedule of Equity Method Investments [Line Items]
Ownership percentage of partner in joint venture	50.00%
Percentage of Company's income (loss) received in final step of distribution		0.5
Allocation of net income and cash flows, percentage	50.00%
Allocation of proceeds from capital transactions, percentage, third priority	80.00%