Revenue Recognition - Representation of Performance Obligations Relate to Nature, Amount, Timing and Uncertainty of Revenue and Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Financial Advisory Segment [Member]
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 1,374,036	$ 1,555,526
Asset Management Segment [Member]
Disaggregation Of Revenue [Line Items]
Net Revenue	1,237,390	1,331,801
Asset Management Segment [Member] \| Management Fees and Other [Member]
Disaggregation Of Revenue [Line Items]
Net Revenue	1,216,115	1,311,286
Asset Management Segment [Member] \| Incentive Fees [Member]
Disaggregation Of Revenue [Line Items]
Net Revenue	$ 21,275	$ 20,515

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration