Investment in Unconsolidated Real Estate Ventures - Summary of Results of Operations of Real Estate Ventures with Interests (Parenthetical) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Schedule Of Equity Method Investments [Line Items]
Provision for impairment of investment in real estate ventures	$ 7.3
Brandywine - AI Venture LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Provision for impairment of investment in real estate ventures	10.4
MAP Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Acquisition deal costs	$ 7.1