Non-controlling Interests (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2012	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Distributions to non-controlling interest holders	$ 593,000
163 Washington Ave Condominiums
Noncontrolling Interest [Line Items]
Noncontrolling members' aggregate investment			500,000
Advisor
Noncontrolling Interest [Line Items]
Distributions to non-controlling interest holders	$ 500,000	$ 0
OP units | Advisor
Noncontrolling Interest [Line Items]
Nonvested Shares outstanding (in shares)				4,270,841
LTIP units | Advisor
Noncontrolling Interest [Line Items]
Nonvested Shares outstanding (in shares)				8,880,579