Loans Receivable, Net - Principal Balance and Net Book Value of Loans Receivable Based on Internal Risk Ratings Footnotes (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loan exposure including senior interests	$ 1,500.0	$ 801.8
2018 Single Asset Securitization
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loan amount, securitized	$ 379.3	$ 735.5

This is the principal amount outstanding for securitized loans only (across all types of loans).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

Name:	us-gaap_PrincipalAmountOutstandingOnLoansSecuritized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant