Mortgage Notes Payable (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 Property		Dec. 31, 2012 Property
Debt Instrument [Line Items]
Mortgages notes payable	$ 1,404,080,000		$ 1,565,599,000
Number of properties securing mortgage notes	49		55
Weighted average interest rate (in hundredths)	5.60%		5.40%
Monthly interest expense	6,100,000
Monthly principal amortization	1,900,000
Mortgages notes payable	1,404,080,000		1,565,599,000
Repayment of debt before the scheduled maturity date, prepayment penalties	The prepayment penalty on the majority of the Company's mortgage notes payable are computed by the greater of (a) 1% of the amount of the principal being prepaid or (b) the present value of the mortgage note payable which is calculated by multiplying the principal being prepaid by the difference between the interest rate of the mortgage note and the stated yield rate on a specified U.S. treasury security as defined in the mortgage note agreement.
Aggregate scheduled principal payments of mortgage notes payable [Abstract]
2014	0
2015	67,461,000
2016	12,390,000
2017	182,731,000
2018	271,156,000
Thereafter	870,342,000
Mortgage notes payable	1,404,080,000		1,565,599,000
Minimum [Member]
Debt Instrument [Line Items]
Remaining terms	1 year		1 year
Maximum [Member]
Debt Instrument [Line Items]
Remaining terms	26 years		27 years
Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Mortgages notes payable	1,236,479,000		1,363,731,000
Aggregate scheduled principal payments of mortgage notes payable [Abstract]
Mortgage notes payable	1,236,479,000		1,363,731,000
Multifamily Housing Mortgage Revenue Bonds [Member]
Debt Instrument [Line Items]
Mortgages notes payable	167,601,000	[1]	201,868,000	[1]
Multifamily housing mortgage revenue bonds, variable interest rate (in hundredths)	1.60%		1.90%
Multifamily housing mortgage revenue bonds credit enhancement and underwriting fees, minimum (in hundredths)	1.20%
Multifamily housing mortgage revenue bonds credit enhancement and underwriting fees, maximum (in hundredths)	1.90%
Percentage of units subject to tenant income criteria (in hundredths)	20.00%
Bond subject to interest rate caps	156,900,000
Aggregate scheduled principal payments of mortgage notes payable [Abstract]
Mortgage notes payable	167,601,000	[1]	201,868,000	[1]
Secured Deeds of Trust [Member]
Debt Instrument [Line Items]
Mortgages notes payable	$ 58,400,000

[1] Variable rate mortgage notes payable consists of multifamily housing mortgage revenue bonds secured by deeds of trust on rental properties and guaranteed by collateral pledge agreements, payable monthly at a variable rate as defined in the Loan Agreement (approximately 1.6% at December 2013 and 1.9% at December 2012) plus credit enhancement and underwriting fees ranging from approximately 1.2% to 1.9%. Among the terms imposed on the properties, which are security for the bonds, is a requirement that 20% of the units are subject to tenant income criteria. Principal balances are due in full at various maturity dates from May 2025 through December 2039. Of these bonds $156.9 million are subject to various interest rate cap agreements which limit the maximum interest rate to such bonds.