Incentive Plans - Summary of Impact of Share-Based Incentive Plans on Compensation and Benefits Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based incentive awards:
Share-based incentive awards	$ 39,671	$ 65,189	$ 180,376	$ 226,272
RSUs [Member]
Share-based incentive awards:
Share-based incentive awards	29,295	37,206	112,435	140,597
PRSUs [Member]
Share-based incentive awards:
Share-based incentive awards	636	14,291	5,627	16,540
Restricted Stock [Member]
Share-based incentive awards:
Share-based incentive awards	5,423	7,274	22,969	24,871
Profits Interest Participation Rights [Member]
Share-based incentive awards:
Share-based incentive awards	4,121	6,224	37,172	42,105
DSUs [Member]
Share-based incentive awards:
Share-based incentive awards	$ 196	$ 194	$ 2,173	$ 2,159