Subsequent Events (Details) (USD $)	0 Months Ended														12 Months Ended			0 Months Ended					12 Months Ended
	Feb. 24, 2014	Feb. 03, 2014	Nov. 01, 2013	Aug. 01, 2013	May 01, 2013	Feb. 01, 2013	Nov. 01, 2012	Aug. 01, 2012	May 01, 2012	Feb. 01, 2012	Nov. 01, 2011	Aug. 01, 2011	May 02, 2011	Feb. 01, 2011	Dec. 31, 2013 Units	Dec. 31, 2012	Dec. 31, 2011	Feb. 03, 2014 Subsequent Event [Member]	Jan. 15, 2014 Dividend Declared [Member]	Dec. 04, 2013 Dividend Declared [Member]	Feb. 03, 2014 350 Eighth [Member]	May 28, 2013 350 Eighth [Member]	Dec. 31, 2013 350 Eighth [Member] Units sqft acre
Subsequent Event [Line Items]
Date joint venture partnership entered																					Feb. 03, 2014
Apartment units owned															13,676								410
Area of land																							3.36
Purchase date of land																						May 28, 2013
Acquisition cost															$ 80,200,000								$ 46,600,000
Area of commercial space																							40,000
Dividends payment date		Feb. 03, 2014
Dividends			$ 0.190000	$ 0.190000	$ 0.190000	$ 0.190000	$ 0.180000	$ 0.180000	$ 0.180000	$ 0.170000	$ 0.170000	$ 0.170000	$ 0.170000	$ 0.170000	$ 0.760000	$ 0.710000	$ 0.680000	$ 0.19
Dividend record date																			Jan. 15, 2014
Dividend declaration date																				Dec. 04, 2013
Disposition date	Feb. 24, 2014
Proceeds from sale of property	60,000,000														139,000,000	67,300,000
Gain on disposition of property	$ 40,000,000.0														$ 52,800,000	$ 26,800,000