Regulatory - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Description of minimum net capital requirements	The greater of $5,000 or 1/15 of aggregate indebtedness
Minimum net capital requirements (greater than $5,000 or 1/15 of aggregate indebtedness)	$ 5,000
Minimum net capital requirements (greater than $5,000 or 1/15 of aggregate indebtedness)	6.67%
Net capital	$ 24,500,000	$ 25,900,000
Excess net capital	$ 23,200,000	$ 24,300,000
Aggregate indebtedness to net capital ratio	0.8	0.9