General, Administrative and Other - Components of General, Administrative and Other Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Income and Expenses [Abstract]
Occupancy and equipment	$ 7,531	$ 7,524	$ 15,136	$ 15,108
Information processing and communications	5,634	5,488	10,658	10,850
Professional services	5,196	6,730	14,945	21,690
Recurring placement and related service fees	3,680	3,503	10,172	6,845
Insurance	2,126	2,172	4,256	4,324
Business development	303	859	1,363	1,957
Foreign exchange gains	(281)	(402)	(310)	(354)
Other expenses	1,526	2,553	4,201	5,795
General, Administrative and Other Expenses before Legal Provisions	25,715	28,427	60,421	66,215
Legal provisions	116,900	0	116,900	0
Total General, Administrative and Other	$ 142,615	$ 28,427	$ 177,321	$ 66,215