Multi-family Loans - Unpaid Principal Balance (Details) - Financial Asset, Equal to or Greater than 90 Days Past Due $ in Thousands	Dec. 31, 2020 USD ($)
Variable Interest Entity [Line Items]
Fair Value	$ 3,325
Unpaid Principal Balance	$ 3,363

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_VariableInterestEntityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration