Investment in Unconsolidated Joint Ventures (DC Charlotte Plaza LLLP) (Details) - DC Charlotte Plaza LLLP ft² in Thousands, $ in Thousands	Dec. 31, 2017 USD ($) ft²
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	282
Cash balance of joint venture | $	$ 611
DFA
Schedule of Equity Method Investments [Line Items]
Ownership percentage of partner in joint venture	50.00%