Fair Value Measurements - Summary of Categorization of Assets and Liabilities Measured at Fair Value (Parenthetical) (Detail) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	Jun. 09, 2021	Mar. 08, 2021	Dec. 31, 2020	Sep. 30, 2020	Aug. 13, 2020	Jun. 16, 2020	May 04, 2020
Fair value of convertible notes			$ 170,191		$ 24,344	$ 145,847
Securrency - Series A Preferred Stock [Member]
Fair value of convertible notes	$ 8,488	$ 8,349
Advisor Engine [Member]
Fair value of financial interest disposed of							$ 9,592
Thesys Group, Inc [Member]
Fair value of financial interest				$ 0