Mortgage Notes Payable (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) property	Dec. 31, 2014 USD ($) property
Debt Instrument [Line Items]
Mortgage notes payable	$ 2,215,077	$ 2,234,317
Number of properties securing mortgage notes | property	64	67
Weighted average interest rate (in hundredths)	4.40%	4.60%
Unamortized debt issuance expense	$ 8,000	$ 11,900
Monthly interest expense	7,500
Monthly principal amortization	2,400
Mortgage notes payable, net	$ 2,215,077	$ 2,234,317
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.
Minimum [Member]
Debt Instrument [Line Items]
Remaining terms	1 year	1 year
Maximum [Member]
Debt Instrument [Line Items]
Remaining terms	31 years	26 years
Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Mortgage notes payable	$ 1,925,985	$ 2,049,577
Prepayment penalty, percent of principal prepaid	1.00%
Multifamily Housing Mortgage Revenue Bonds [Member]
Debt Instrument [Line Items]
Mortgage notes payable	$ 289,092	$ 184,740
Multifamily housing mortgage revenue bonds, variable interest rate (in hundredths)	1.20%	1.80%
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	$ 257,300
Multifamily Housing Mortgage Revenue Bonds [Member] | Total Return Swap [Member]
Debt Instrument [Line Items]
Bond subject to interest rate caps	20,700
Secured Debt [Member]
Debt Instrument [Line Items]
Mortgage notes payable	2,158,267
Debt instrument, unamortized premium	64,800	$ 83,800
Secured Deeds of Trust [Member]
Debt Instrument [Line Items]
Mortgage notes payable, net	$ 48,500