Collateralized Transactions - Additional Information (Detail) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Securities Financing Transaction [Line Items]
Securities loaned		$ 13,902,000
CF & Co [Member]
Securities Financing Transaction [Line Items]
Securities loaned	$ 0	$ 13,900,000
Stated interest rate		2.45%
CF & Co [Member] \| Securities Financing Transaction, Fair Value [Member]
Securities Financing Transaction [Line Items]
Securities loaned		$ 13,900,000
CF & Co [Member] \| Securities Financing Transaction, Fair Value [Member] \| Fair Value [Member]
Securities Financing Transaction [Line Items]
Securities loaned		$ 13,900,000

Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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