The Bonds that are subject to interest rate cap agreements.

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fixed interest rate related to the interest rate derivative.

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Amount of increase in the fair value of derivatives recognized in the income statement.

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Nominal or face amount used to calculate payment on derivative.

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The number of derivative instruments of a particular group held by the entity.

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Derivative Instruments and Hedging Activities (Details)	3 Months Ended		6 Months Ended
Derivative Instruments and Hedging Activities (Details)	Jun. 30, 2020 USD ($) instrument	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) instrument	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Derivative [Line Items]
Total return swap income	$ 2,788,000	$ 1,975,000	$ 4,772,000	$ 4,020,000
Multifamily Housing Mortgage Revenue Bonds
Derivative [Line Items]
Bond subject to interest rate caps	255,100,000		255,100,000
Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Derivative, notional amount	$ 175,000,000.0		$ 175,000,000.0
Interest rate	2.30%		2.30%
Aggregate carrying value of the interest rate swap contracts	$ (3,400,000)		$ (3,400,000)		$ 800,000
Aggregate carrying value of the interest rate swap contracts, asset	0		0		1,000,000.0
Aggregate carrying value of the interest rate swap contracts, liability	3,400,000		3,400,000		200,000
Not Designated as Hedging Instrument \| Total Return Swap, Callable
Derivative [Line Items]
Derivative, notional amount	255,100,000		255,100,000
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