Derivative Instruments and Hedging Activities (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Derivative [Line Items]
Total return swap income	$ 3,123,000	$ 0
Multifamily Housing Mortgage Revenue Bonds [Member]
Derivative [Line Items]
Bond subject to interest rate caps	257,300,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 225,000,000
Interest rate (in hundredths)	2.40%
Aggregate carrying value of the interest rate swap contracts	$ 1,000,000		$ 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
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member] | Interest Rate Cap [Member]
Derivative [Line Items]
Derivative, notional amount	20,700,000
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member] | Swap [Member]
Derivative [Line Items]
Derivative, fair value, net	13,000		$ 4,000
Not Designated as Hedging Instrument [Member] | Total Return Swap, Callable [Member]
Derivative [Line Items]
Derivative, notional amount	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