Derivative Instruments and Hedging Activities (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2016 USD ($) instrument	Dec. 31, 2016 USD ($) instrument	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Unsecured debt, net		$ 3,246,779,000	$ 3,088,680,000
Total return swap income		11,716,000	5,655,000	$ 0
Variable rate term loan [Member]
Derivative [Line Items]
Unsecured debt, net	$ 350,000,000	$ 100,000,000	225,000,000
Debt instrument, term	5 years
Basis spread on rate (in hundredths)		0.95%
Derivative, notional amount	$ 200,000,000.0		225,000,000
Multifamily Housing Mortgage Revenue Bonds [Member]
Derivative [Line Items]
Bond subject to interest rate caps		$ 257,300,000
Interest Rate Swap [Member] | Variable rate term loan [Member]
Derivative [Line Items]
Unsecured debt, net		$ 100,000,000
Number of derivative instruments held | instrument		4
Total Return Swap [Member] | Multifamily Housing Mortgage Revenue Bonds [Member]
Derivative [Line Items]
Bond subject to interest rate caps		$ 20,700,000
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Hedge ineffectiveness related to cash flow hedges		300,000	0	$ 0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Number of derivative instruments held | instrument	4
Derivative, notional amount		$ 150,000,000.0
Average fixed interest rate (as a percent)		2.20%
Derivative, fair value		$ 4,400,000	0
Aggregate carrying value of the interest rate swap contracts		33,100	1,000,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Variable rate term loan [Member]
Derivative [Line Items]
Derivative, notional amount		25,000,000.0
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total return swap income		11,700,000	5,700,000
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative [Line Items]
Derivative, notional amount		20,700,000.0
Derivative, fair value		$ 0	0
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member]
Derivative [Line Items]
Number of derivative instruments held | instrument		4
Derivative, fair value		$ 0	$ 4,000
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member] | Multifamily Housing Mortgage Revenue Bonds [Member]
Derivative [Line Items]
Bond subject to interest rate caps		$ 257,300,000
Not Designated as Hedging Instrument [Member] | Total Return Swap [Callable]
Derivative [Line Items]
Number of derivative instruments held | instrument		1
Derivative, notional amount		$ 114,400,000
Not Designated as Hedging Instrument [Member] | Total Return Swap, Jan 1, 2017 [Member]
Derivative [Line Items]
Number of derivative instruments held | instrument		3
Derivative, notional amount		$ 142,900,000