Notes Payable, Unsecured Notes and Credit Facility (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2014 item	Dec. 31, 2013
Mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Amount drawn	$ 1,010,883,000	$ 1,011,609,000
Mortgage notes payable held by wholly owned subsidiaries guaranteed by the Company	289,597,000
Term Loan
Notes Payable, Unsecured Notes and Credit Facility
Principal amount of notes issued	300,000,000
Amount drawn	250,000,000
Additional amount with option to draw	50,000,000
Variable rate unsecured credit facility
Notes Payable, Unsecured Notes and Credit Facility
Available borrowing capacity	1,300,000,000
Line of credit facility, extension period	1 year
Number of extension options	2
Extension period under each option	6 months
Extension fee	1,950,000
Period of borrowing rate assumed	1 month
Annual facility fee	1,950,000
Borrowings outstanding under the credit facility	0	0
Outstanding balance of letters of credit	52,300,000	65,018,000
Net carrying value of apartment communities and improved land parcels securing debt	$ 4,445,256,000
Fixed rate mortgage notes payable
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)	4.50%	4.50%
Variable rate mortgage notes payable, unsecured term loan and Credit Facility
Notes Payable, Unsecured Notes and Credit Facility
Weighted average interest rate, debt (as a percent)	1.80%	1.80%
LIBOR | Variable rate unsecured credit facility
Notes Payable, Unsecured Notes and Credit Facility
Debt instrument variable rate	LIBOR
Debt instrument, basis spread on variable rate (as a percent)	1.05%
Current interest rate (as a percent)	1.20%