Real Estate (Details) (USD $)	0 Months Ended	6 Months Ended	18 Months Ended
	Jan. 02, 2014	Jun. 30, 2014	Jun. 30, 2014
Significant Acquisitions and Disposals [Line Items]
Contributions from noncontrolling interests		$ 65,350,000
GroveatShrewsbury [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Real Estate Property	187,000
Price to Acquire Non-Controlling Interest		9,000,000	9,000,000
Brook 35 [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Real Estate Property	99,000
GroveatShrewsbury & Brook 35 [Member]
Significant Acquisitions and Disposals [Line Items]
Gross Value of Business Acquisition	161,000,000
Effective Economic Interest Acquisition	84.00%
Noncash or Part Noncash Acquisition, Debt Assumed	68,000,000
Number of downREIT Operating Partnership Units Issued in Connection with Business Acquisition	632,000
Business Acquisition, Cost of Acquired Entity, Cash Paid	13,000,000
Business Acquisition Net Assets Allocated Below Market Lease	2,300,000
Contributions from noncontrolling interests	71,100,000
Business Combination, Acquisition Related Costs		900,000	2,000,000
Above Market Leases [Member] | GroveatShrewsbury & Brook 35 [Member]
Significant Acquisitions and Disposals [Line Items]
Business Acquisition Net Assets Allocated Above Market Leases	$ 1,700,000