General, Administrative and Other - Components of General, Administrative and Other Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
Professional services	$ 42,370	$ 52,163	$ 43,343
Occupancy and equipment	30,281	28,769	33,358
Information processing and communications	21,443	25,917	28,274
Recurring placement and related service fees	14,034	16,247	20,153
Insurance	8,658	7,391	7,609
Business development	4,048	4,075	6,685
Foreign exchange (gains) and losses	(451)	2,766	(726)
Other expenses	10,478	12,899	13,375
General and Administrative Expense before Legal Settlements and Provisions	130,861	150,227	152,071
Legal settlements and provisions	19,100	31,750	0
Total General, Administrative and Other	$ 149,961	$ 181,977	$ 152,071