Investments - Details of Investments Carried at Cost (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 27, 2019	Dec. 31, 2018
Investment [Line Items]
Investments	$ 11,192		$ 28,080
Advisor Engine [Member] | Convertible Preferred Stock [Member]
Investment [Line Items]
Investments			25,000
Thesys Group, Inc [Member]
Investment [Line Items]
Investments	3,080		$ 3,080
Securrency Inc [Member] | Convertible Preferred Stock [Member]
Investment [Line Items]
Investments	$ 8,112	$ 8,112