Mortgage Loans on Real Estate (Parenthetical) (Detail) $ in Millions	Dec. 31, 2019 USD ($)
Mortgage Loans On Real Estate [Abstract]
Aggregate cost for federal income tax	$ 208.1

Amount of federal income tax basis of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Footnote 8
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 8))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Name:	srt_MortgageLoansOnRealEstateFederalIncomeTaxBasis1
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant