Concentrations of Credit Risk	12 Months Ended
Dec. 31, 2019
Risks and Uncertainties [Abstract]
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that could potentially expose us to concentrations of credit risk include our unsecured receivables from the Exchange. A large majority of our revenue and receivables are from the Exchange and its affiliates. See also Note 1, "Nature of Operations". Management fee amounts and other reimbursements due from the Exchange and its affiliates were $468.6 million and $449.9 million at December 31, 2019 and 2018, respectively. Given the financial strength of the Exchange and historical experience of no credit losses, we believe it is unlikely these receivables have a significant credit loss exposure.

The entire disclosure for any concentrations existing at the date of the financial statements that make an entity vulnerable to a reasonably possible, near-term, severe impact. This disclosure informs financial statement users about the general nature of the risk associated with the concentration, and may indicate the percentage of concentration risk as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-URI http://asc.fasb.org/topic&trid=2134479

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