Derivative Instruments and Hedging Activities (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) instrument	Dec. 31, 2014 USD ($) instrument	Dec. 31, 2013 USD ($)
Derivative [Line Items]
Total return swap income	$ 5,655,000	$ 0	$ 0
Multifamily Housing Mortgage Revenue Bonds [Member]
Derivative [Line Items]
Bond subject to interest rate caps	257,300,000
Designated as Hedging Instrument [Member] | Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 225,000,000
Interest rate (in hundredths)	2.40%
Designated as Hedging Instrument [Member] | Swap [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 225,000,000.0
Aggregate carrying value of the interest rate swap contracts	1,000,000	1,800,000
Designated as Hedging Instrument [Member] | Interest Rate Cap [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Aggregate carrying value of the interest rate swap contracts	0	$ 0
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
Not Designated as Hedging Instrument [Member] | Swap [Member] | Total Return Swap [Member]
Derivative [Line Items]
Number of derivative instruments held | instrument	4	0
Derivative, fair value	$ 4,000
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member] | Total Return Swap [Member]
Derivative [Line Items]
Derivative, notional amount	$ 20,700,000