Investments - Details of Investments Carried at Cost (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Securrency Inc. - Carrying Value [Member]
Investments	$ 13,849	$ 8,112
Securrency Inc. - Cost [Member]
Investments	13,612	8,112
Securrency Inc. - Series A Convertible Preferred Stock - Carrying Value [Member]
Investments	8,349	8,112
Securrency Inc. - Series A Convertible Preferred Stock - Cost [Member]
Investments	8,112	8,112
Securrency Inc. - Series B Convertible Preferred Stock - Carrying Value [Member]
Investments	5,500	0
Securrency Inc. - Series B Convertible Preferred Stock - Cost [Member]
Investments	$ 5,500	$ 0