Notes Payable, Unsecured Notes and Credit Facility (Details) (USD $)			0 Months Ended						1 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Feb. 27, 2013 Archstone Enterprise LP	Sep. 30, 2013 Archstone Enterprise LP	Sep. 30, 2013 Unsecured notes	Dec. 31, 2012 Unsecured notes	Sep. 30, 2013 Mortgage notes payable	Dec. 31, 2012 Mortgage notes payable	Mar. 31, 2013 4.95% unsecured notes	Sep. 30, 2013 3.63% unsecured notes	Apr. 30, 2013 3.06% fixed rate secured mortgage loan	Apr. 30, 2013 4.69% secured mortgage note	May 31, 2013 5.55% secured notes	May 31, 2013 3.08% fixed-rate secured mortgage loan	May 31, 2013 5.24% fixed rate secured mortgage note	May 31, 2013 Variable rate secured mortgage note
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes					$ 2,250,000,000	$ 1,950,000,000	$ 2,710,673,000	$ 1,427,133,000
Variable rate notes							1,011,609,000	476,935,000
Total notes payable and unsecured notes	5,972,282,000	3,854,068,000			2,250,000,000		3,512,067,000
Total mortgage notes payable, unsecured notes and Credit Facility	5,972,282,000	3,854,068,000
Amount of debt discount					4,809,000	4,202,000
Amount of debt premium							130,159,000	1,167,000
Repayment of debt			1,477,720,000						100,000,000
Principal amount of notes issued											15,000,000			56,210,000
Principal amount of notes issued										400,000,000						47,000,000
Net proceeds from issuance of debt										396,212,000
Principal amount of debt repaid												170,125,000	5,393,000		52,806,000
Stated interest rate (as a percent)					3.625%				4.95%	3.63%	3.06%	4.69%	5.55%	3.08%	5.24%
Effective interest rate, percentage										3.79%
Assumed principal amount of indebtedness			$ 3,512,202,000	$ 3,512,202,000