Credit Risk	12 Months Ended
Credit Risk	Dec. 31, 2021
Risks and Uncertainties [Abstract]
Credit Risk	Credit Risk In the normal course of business the Company, as agent, executes transactions with, and on behalf of, other brokers and dealers. If the agency transactions do not settle because of failure to perform by either counterparty, the Company will recognize a receivable from (and a matching payable to) brokers and dealers and clearing organizations for the proceeds from the unsettled transaction, until the failed transaction settles. The Company may be obligated to discharge the obligation of the non-performing party and, as a result, may incur a loss if the market value of the security is different from the contract amount of the transaction. However, from time to time, the Company enters into repurchase and/or reverse repurchase agreements to facilitate the clearance of securities relating to fails to deliver or receive. Credit exposure related to these agreements to repurchase, including the risk related to a decline in market value of collateral (pledged or received), is managed by entering into agreements to repurchase with overnight or short-term maturity dates and only entering into repurchase transactions with netting members of the Fixed Income Clearing Corporation (“FICC”). The FICC operates a continuous net settlement system, whereby as trades are submitted and compared, the FICC becomes the counterparty. A substantial number of the Company’s transactions are collateralized and executed with, and on behalf of, a limited number of broker-dealers. The Company’s exposure to credit risk associated with the nonperformance of these clients in fulfilling their contractual obligations pursuant to securities transactions can be directly impacted by volatile trading markets which may impair the clients’ ability to satisfy their obligations to the Company. The Company does not expect nonperformance by counterparties in the above situations. However, the Company’s policy is to monitor its market exposure and counterparty risk. In addition, the Company has a policy of reviewing, as considered necessary, the credit standing of each counterparty with which it conducts business. Allowance for Credit Losses The Company may be exposed to credit risk regarding its receivables, which are primarily receivables from financial institutions, including investment managers and broker-dealers. The Company maintains an allowance for credit losses based upon an estimate of the amount of potential credit losses in existing accounts receivable, as determined from a review of aging schedules, past due balances, historical collection experience and other specific account data. Careful analysis of the financial condition of our counterparties is also performed. The Company has evaluated its loss assumptions as a result of the COVID-19 pandemic and determined the current estimate of expected credit losses remains reasonable due to continued strong collections and no deterioration in the accounts receivable aging. Account balances are pooled based on the following risk characteristics: •Geographic location •Transaction fee type (billing type) •Legal entity Write-Offs Once determined uncollectible, aged balances are written off against the allowance for credit losses. This determination is based on careful analysis of individual receivables and aging schedules, which are disaggregated based on the risk characteristics described above. Based on current policy, this generally occurs when the receivable is 360 days past due. As of December 31, 2021 and 2020, the Company maintained an allowance for credit losses with regard to these receivables of $0.3 million and $0.2 million, respectively. For the years ended December 31, 2021 and 2020, the Company recognized a credit loss expense of $13 thousand and $0.1 million, respectively. For the year ended December 31, 2019, recoveries resulted in a net reversal of credit loss expense totaling $1.0 million.