Consolidated VIEs - Summary of Consolidated VIE Assets and Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ASSETS
Cash and cash equivalents	$ 974,696	$ 1,389,876
Customers and other receivables	183,376	121,261
Investments	782,351	658,532
Other assets	452,252	307,332
Total Assets	6,209,559	5,971,861
Liabilities:
Deposits and other customer payables	1,239,716	1,201,150
Other liabilities	563,427	524,538
Total Liabilities	4,767,860	4,972,428
Consolidated VIEs [Member]
ASSETS
Cash and cash equivalents	2,425	3,558
Customers and other receivables	108	160
Investments	217,876	158,370
Other assets	767	400
Total Assets	221,176	162,488
Liabilities:
Deposits and other customer payables	67	104
Other liabilities	469	491
Total Liabilities	$ 536	$ 595