Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Foreign currency remeasurement gains (losses), net of hedge transactions	$ 1,900,000	$ (1,153,000)	$ 1,589,000
Depreciation and amortization expense	$ 31,498,000	33,264,000	32,785,000
Annual date of goodwill impairment	Nov. 01, 2017
Goodwill impairment loss	$ 0	0	0
Recoverable expenses	17,793,000	16,998,000	19,358,000
Soft dollar arrangement expenses	$ 24,000,000
Operating Segments [Member] | Financial Advisory Segment [Member]
Significant Accounting Policies [Line Items]
Fees receivable outstanding past due	60 days from the date of invoice
Contractual payment term description relating to our interest-bearing financing receivables	Financial Advisory transactions include specific contractual payment terms that may vary from one month to four years (as is the case for our interest-bearing financing receivables) following the invoice date or may be subject to court approval (as is the case with bankruptcy-related restructuring assignments). In such cases, receivables are deemed past due when payment is not received by the agreed-upon contractual date or the court approval date, respectively.
Period receivables past due in excess of 180 days are fully provided unless there is evidence that the balance is collectible	180 days
Depreciation and amortization expense	$ 6,596,000	5,661,000	4,412,000
Operating Segments [Member] | Asset Management Segment [Member]
Significant Accounting Policies [Line Items]
Fees receivable outstanding past due	12 months after the invoice date
Depreciation and amortization expense	$ 2,830,000	$ 3,666,000	$ 2,957,000