Derivative Instruments and Hedging Activities (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) instrument	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) instrument	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Derivative [Line Items]
Total return swap income	$ 2,660,000	$ 2,977,000	$ 8,137,000	$ 7,749,000
Multifamily Housing Mortgage Revenue Bonds
Derivative [Line Items]
Bond subject to interest rate caps	224,500,000		224,500,000
Total Return Swap, Callable
Derivative [Line Items]
Total return swap income	2,700,000	$ 3,000,000	8,100,000	$ 7,700,000
Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Aggregate carrying value of the interest rate swap contracts, liability	0		0		$ 2,400,000
Aggregate carrying value of the interest rate swap contracts, asset	0		0		0
Not Designated as Hedging Instrument | Total Return Swap, Callable
Derivative [Line Items]
Derivative, notional amount	224,500,000		224,500,000
Derivative, fair value, net	$ 0		$ 0		$ 0
Not Designated as Hedging Instrument | Total Return Swap, Callable | Multifamily Housing Mortgage Revenue Bonds
Derivative [Line Items]
Number of derivative instruments | instrument	4		4