Revenue and Accounts Receivable - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investment Banking [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	$ 3,204,519	$ 2,238,156	$ 1,933,364
Investment Banking [Member] | Advisory Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	2,751,992	1,755,273	1,653,585
Investment Banking [Member] | Underwriting Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	246,705	276,191	89,681
Investment Banking [Member] | Commissions and Related Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	205,822	206,692	190,098
Investment Management [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	65,784	54,397	50,611
Investment Management [Member] | Wealth Management [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	65,784	53,069	48,083
Investment Management [Member] | Institutional Asset Management [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	$ 0	$ 1,328	$ 2,528