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Equity-Method Eligible Investments - Carrying Values of Equity Method Eligible Investments Recorded within Other Long-Term Investments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	May 07, 2020	May 06, 2020
Investments in unconsolidated affiliates
Other long-term investments	$ 1,285.5	$ 786.8
Kudu investments
Investments in unconsolidated affiliates
Other long-term investments	$ 604.7	$ 400.6
Kudu investments | Minimum
Investments in unconsolidated affiliates
Ownership interest (as a percent)	3.20%	3.20%
Kudu investments | Maximum
Investments in unconsolidated affiliates
Ownership interest (as a percent)	32.70%	35.00%
Marketing Technology (MediaAlpha)
Investments in unconsolidated affiliates
Ownership interest (as a percent)	28.40%	35.00%
Other long-term investments	$ 316.4	$ 802.2
PassportCard/DavidShield
Investments in unconsolidated affiliates
Ownership interest (as a percent)	53.80%	53.80%	53.80%	50.00%
Other long-term investments	$ 105.0	$ 95.0
Elementum Holdings L.P.
Investments in unconsolidated affiliates
Ownership interest (as a percent)	29.70%	28.90%
Other long-term investments	$ 56.7	$ 55.1
Other
Investments in unconsolidated affiliates
Other long-term investments	95.6	132.2
Equity Method Investments
Investments in unconsolidated affiliates
Other long-term investments	$ 17.2	$ 15.2

X

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
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Amount of long-term investments classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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No definition available.

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