Notes Payable, Unsecured Notes and Credit Facility (Details) (USD $)			0 Months Ended						1 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Feb. 27, 2013 Archstone Enterprise LP	Jun. 30, 2013 Archstone Enterprise LP	Jun. 30, 2013 Unsecured notes	Dec. 31, 2012 Unsecured notes	Jun. 30, 2013 Mortgage notes payable	Dec. 31, 2012 Mortgage notes payable	Mar. 31, 2013 4.95% medium term notes	Apr. 30, 2013 3.06% fixed rate secured mortgage note	Apr. 30, 2013 4.69% secured mortgage note	May 31, 2013 5.55% secured notes	May 31, 2013 3.08% fixed-rate secured mortgage note	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					$ 1,850,000,000	$ 1,950,000,000	$ 2,714,321,000	$ 1,427,133,000
Variable rate notes							1,011,709,000	476,935,000
Total notes payable and unsecured notes	5,576,030,000	3,854,068,000			1,850,000,000		3,495,052,000
Credit Facility	142,000,000
Total mortgage notes payable, unsecured notes and Credit Facility	5,718,030,000	3,854,068,000
Amount of debt discount					3,887,000	4,202,000
Amount of debt premium							139,175,000	1,167,000
Repayment of debt			1,477,720,000						100,000,000						47,000,000
Principal amount of notes issued													56,210,000
Principal amount of debt repaid										15,000,000	170,125,000	5,393,000		52,806,000
Stated interest rate (as a percent)									4.95%	3.06%	4.69%	5.55%	3.08%	5.24%
Assumed principal amount of indebtedness			$ 3,512,202,000	$ 3,512,202,000