Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 multiplier person community	Dec. 31, 2012	Dec. 31, 2011
Employment agreements and arrangements
Number of executive officers under agreement	3
Number of executives, case one	2
Compensation multiplier, case one	2
Compensation multiplier, if the termination is in connection with a sale of the company, case one	3
Number of executives, case two	1
Compensation multiplier, case two	1
Compensation multiplier, if the termination is in connection with a sale of the company, case two	2
Lease obligations
Cost related to operating lease	$ 17,996,000	$ 17,604,000	$ 16,887,000
Number of development rights owned	46
Properties on land subject to land leases
Lease obligations
Number of apartment communities	11
Number of communities under construction	3
Number of commercial properties owned	2
Number of leased properties accounted for as operating leases	14
Number of leased properties with purchase options	4
Assets Held under Capital Leases
Lease obligations
Number of development rights owned	2
Capital lease obligation	$ 33,879,000
Restricted stock and stock options
Employment agreements and arrangements
Retirement age	50 years
Period of the non-compete agreement	1 year
Restricted stock and stock options | Minimum
Employment agreements and arrangements
Service period	10 years
Employee's age at retirement plus years of employment	70 years
Written notice period	6 months
Restricted stock and stock options | Maximum
Employment agreements and arrangements
Options exercise period upon termination without cause or retirement	12 months
Officer Severance Program | Vice presidents and senior vice presidents
Employment agreements and arrangements
Compensation multiplier	1
Officer Severance Program | Executive vice presidents
Employment agreements and arrangements
Compensation multiplier	2
Officer Severance Program | Maximum
Employment agreements and arrangements
Termination period following a sale event	18 months