Derivative Instruments and Hedging Activities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Derivative [Line Items]
Cash flow hedge ineffectiveness	$ 0	$ 0	$ 0	$ 0
Total return swap income	3,143,000	$ 0	9,080,000	$ 0
Multifamily Housing Mortgage Revenue Bonds [Member]
Derivative [Line Items]
Bond subject to interest rate caps	257,300,000		257,300,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 225,000,000		$ 225,000,000
Interest rate (in hundredths)	2.40%		2.40%
Aggregate carrying value of the interest rate swap contracts	$ 200,000		$ 200,000		$ 1,000,000
Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative [Line Items]
Aggregate carrying value of the interest rate swap contracts	0		0		0
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member]
Derivative [Line Items]
Derivative, notional amount	20,700,000		20,700,000
Derivative, fair value, net	16,000		16,000		$ 4,000
Not Designated as Hedging Instrument [Member] | Total Return Swap, Callable [Member]
Derivative [Line Items]
Derivative, notional amount	114,400,000		114,400,000
Not Designated as Hedging Instrument [Member] | Total Return Swap, January 1, 2017 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 142,900,000		$ 142,900,000