Performance Bonds and Guaranty Fund Contributions (Details) $ in Billions	6 Months Ended
Jun. 30, 2020 USD ($)
Guarantor Obligations [Line Items]
Average Daily Clearing Settlement	$ 5.9
Federal Reserve Reinvestment [Member]
Guarantor Obligations [Line Items]
Cash Equivalents, at Carrying Value	52.9
U.S. Treasury Performance Bond [Member]
Guarantor Obligations [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3.5
Available-for-sale Securities at Fair Value	3.5
U.S. Government Agency Security Performance Bond [Member]
Guarantor Obligations [Line Items]
Available-for-sale Securities, Amortized Cost Basis	0.3
Available-for-sale Securities at Fair Value	$ 0.3

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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+ References

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