Variable Interest Entities - Summary of Information about Variable Interests (Detail) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Carrying Amount - Assets
Total net carrying value	$ 8,500,000	$ 36,284,000
Maximum exposure to loss	16,612,000	36,284,000
Advisor Engine [Member]
Carrying Amount - Assets
Unsecured convertible notes receivable		2,126,000
Unsecured non-convertible note receivable	8,500,000	26,046,000
Preferred stock	0	0
Total net carrying value	8,500,000	28,172,000
Securrency Inc [Member]
Carrying Amount - Assets
Preferred stock	$ 8,112,000	$ 8,112,000