New Accounting Pronouncements (Policies)	6 Months Ended
Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Recently Adopted Accounting Guidance	Recently Adopted Accounting Guidance Income Taxes In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes,” which is intended to simplify various aspects related to accounting for income taxes. This accounting update removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. We prospectively adopted the accounting update on January 1, 2021. The adoption did not have a material impact on our consolidated financial statements.
Revenue Recognition	Commissions. We earn commission revenue by executing, settling, and clearing transactions for clients primarily in OTC and listed equity securities, insurance products, and options. Trade execution and clearing and custody services, when provided together, represent a single performance obligation as the services are not separately identifiable in the context of the contract. Commission revenues associated with combined trade execution and clearing and custody services, as well as trade execution services on a standalone basis, are recognized at a point in time on trade-date. Commission revenues are generally paid on settlement date and we record a receivable between trade-date and payment on settlement date. Investment Banking. We provide our clients with a full range of capital markets and financial advisory services. Capital markets services include underwriting and placement agent services in both the equity and debt capital markets, including private equity placements, initial public offerings, follow-on offerings, underwriting and distributing public and private debt. Capital raising revenues are recognized at a point in time on trade-date, as the client obtains the control and benefit of the capital markets offering at that point. Costs associated with capital raising transactions are deferred until the related revenue is recognized or the engagement is otherwise concluded, and are recorded on a gross basis within other operating expenses in the consolidated statements of operations as we are acting as a principal in the arrangement. Any expenses reimbursed by our clients are recognized as investment banking revenues. Revenues from financial advisory services primarily consist of fees generated in connection with merger, acquisition and restructuring transactions. Advisory fees from mergers and acquisitions engagements are recognized at a point in time when the related transaction is completed, as the performance obligation is to successfully broker a specific transaction. Fees received prior to the completion of the transaction are deferred within accounts payable and accrued expenses on the consolidated statements of financial condition. Advisory fees from restructuring engagements are recognized over time using a time elapsed measure of progress as our clients simultaneously receive and consume the benefits of those services as they are provided. A significant portion of the fees we receive for our advisory services are considered variable as they are contingent upon a future event (e.g., completion of a transaction or third party emergence from bankruptcy) and are excluded from the transaction price until the uncertainty associated with the variable consideration is subsequently resolved, which is expected to occur upon achievement of the specified milestone. Payment for advisory services are generally due promptly upon completion of a specified milestone or, for retainer fees, periodically over the course of the engagement. We recognize a receivable between the date of completion of the milestone and payment by the customer. Expenses associated with investment banking advisory engagements are deferred only to the extent they are explicitly reimbursable by the client and the related revenue is recognized at the same time as the associated expense. All other investment banking advisory related expenses, including expenses incurred related to restructuring assignments, are expensed as incurred. All investment banking advisory expenses are recognized within other operating expenses on the consolidated statements of operations and any expenses reimbursed by our clients are recognized as investment banking revenues. Asset Management Fees. We earn management and performance fees in connection with investment advisory services provided to institutional and individual clients. Investment advisory fees are charged based on the value of assets in fee-based accounts and are affected by changes in the balances of client assets due to market fluctuations and levels of net new client assets. Fees are charged either in advance based on fixed rates applied to the value of the customers’ account at the beginning of the period or periodically based on contracted rates and account performance. Contracts can be terminated at any time with no incremental payments due to our company upon termination. If the contract is terminated by the customer fees are prorated for the period and fees charged for the post termination period are refundable to the customer.

New Accounting Pronouncements (Policies)

6 Months Ended

Jun. 30, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Income Taxes

In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes,” which is intended to simplify various aspects related to accounting for income taxes. This accounting update removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. We prospectively adopted the accounting update on January 1, 2021. The adoption did not have a material impact on our consolidated financial statements.

Revenue Recognition

Commissions. We earn commission revenue by executing, settling, and clearing transactions for clients primarily in OTC and listed equity securities, insurance products, and options. Trade execution and clearing and custody services, when provided together, represent a single performance obligation as the services are not separately identifiable in the context of the contract. Commission revenues associated with combined trade execution and clearing and custody services, as well as trade execution services on a standalone basis, are recognized at a point in time on trade-date. Commission revenues are generally paid on settlement date and we record a receivable between trade-date and payment on settlement date.

Investment Banking. We provide our clients with a full range of capital markets and financial advisory services. Capital markets services include underwriting and placement agent services in both the equity and debt capital markets, including private equity placements, initial public offerings, follow-on offerings, underwriting and distributing public and private debt.

Capital raising revenues are recognized at a point in time on trade-date, as the client obtains the control and benefit of the capital markets offering at that point. Costs associated with capital raising transactions are deferred until the related revenue is recognized or the engagement is otherwise concluded, and are recorded on a gross basis within other operating expenses in the consolidated statements of operations as we are acting as a principal in the arrangement. Any expenses reimbursed by our clients are recognized as investment banking revenues.

Revenues from financial advisory services primarily consist of fees generated in connection with merger, acquisition and restructuring transactions. Advisory fees from mergers and acquisitions engagements are recognized at a point in time when the related transaction is completed, as the performance obligation is to successfully broker a specific transaction. Fees received prior to the completion of the transaction are deferred within accounts payable and accrued expenses on the consolidated statements of financial condition. Advisory fees from restructuring engagements are recognized over time using a time elapsed measure of progress as our clients simultaneously receive and consume the benefits of those services as they are provided. A significant portion of the fees we receive for our advisory services are considered variable as they are contingent upon a future event (e.g., completion of a transaction or third party emergence from bankruptcy) and are excluded from the transaction price until the uncertainty associated with the variable consideration is subsequently resolved, which is expected to occur upon achievement of the specified milestone. Payment for advisory services are generally due promptly upon completion of a specified milestone or, for retainer fees, periodically over the course of the engagement. We recognize a receivable between the date of completion of the milestone and payment by the customer. Expenses associated with investment banking advisory engagements are deferred only to the extent they are explicitly reimbursable by the client and the related revenue is recognized at the same time as the associated expense. All other investment banking advisory related expenses, including expenses incurred related to restructuring assignments, are expensed as incurred. All investment banking advisory expenses are recognized within other operating expenses on the consolidated statements of operations and any expenses reimbursed by our clients are recognized as investment banking revenues.

Asset Management Fees. We earn management and performance fees in connection with investment advisory services provided to institutional and individual clients. Investment advisory fees are charged based on the value of assets in fee-based accounts and are affected by changes in the balances of client assets due to market fluctuations and levels of net new client assets. Fees are charged either in advance based on fixed rates applied to the value of the customers’ account at the beginning of the period or periodically based on contracted rates and account performance. Contracts can be terminated at any time with no incremental payments due to our company upon termination. If the contract is terminated by the customer fees are prorated for the period and fees charged for the post termination period are refundable to the customer.