Investment in Unconsolidated Ventures Notes Receivable (Details) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Jul. 31, 2014	Dec. 31, 2013	Oct. 17, 2014 Real_Estate_Investments	Oct. 16, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Real Estate Investments in residential towers	1
Equity Method Investment, Summarized financial information debt	965,077,000
Financing Receivable, Net	88,000,000		7,026,000
Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short-term Debt, Terms	4.0% through December 31, 2014, (ii) 5.0% from January 1, 2015 through January 31, 2015, (iii) 7.0% from February 1, 2015 through February 28, 2015 and (iv) 9.0% from March 1, 2015 through March 31, 2015.
River Place [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Net	88,000,000
Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Rentable Area		232,274
Equity Method Investment, Summarized financial information debt	382,100,000	34,500,000
Equity method investments, Cash contributions	69,000,000	12,800,000
Equity method investments, Closing costs	200,000	100,000
Equity method investments, Purchase adjustments		900,000
Equity method investments, Credit from seller		600,000
Number of Real Estate Properties		2		7
Austin, Texas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of floors of a building		3
Secured Debt [Member] | Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short-term Debt, Terms	0.05
DRA Advisors LLC [Member] | Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity method investments, Closing costs					$ 1,900,000