Summary of Significant Accounting Policies - Schedule of Recognized Revenues (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 2,218,132	$ 2,047,579	$ 1,596,450
Leasing and other commissions
Segment Reporting Information [Line Items]
Revenues	854,780	817,435	616,980
Capital markets commissions
Segment Reporting Information [Line Items]
Revenues	541,255	468,904	397,736
Gains from mortgage banking activities/originations, net
Segment Reporting Information [Line Items]
Revenues	198,085	182,264	206,000
Management services, servicing fees and other
Segment Reporting Information [Line Items]
Revenues	$ 624,012	$ 578,976	$ 375,734