Investments - Details of Investments Carried at Cost (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Dec. 27, 2019	Dec. 31, 2018
Investment [Line Items]
Investments	$ 11,192	$ 11,192
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	$ 8,112