Unconsolidated Affiliates - Schedule of Investments in Unconsolidated Affiliates (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Carrying Value	$ 219.7	$ 225.6
Excess carrying value of investment over proportionate share of net assets	$ 139.3	143.8
International Financial Data Services L.P. [Member]
Schedule of Investments [Line Items]
Ownership Percentage	50.00%
Carrying Value	$ 88.1	97.5
Excess carrying value of investment over proportionate share of net assets	$ 39.0	41.5
Pershing Road Development Company, LLC [Member]
Schedule of Investments [Line Items]
Ownership Percentage	50.00%
Carrying Value	$ 76.8	74.1
Excess carrying value of investment over proportionate share of net assets	$ 70.9	72.7
Broadway Square Partners, LLP [Member]
Schedule of Investments [Line Items]
Ownership Percentage	50.00%
Carrying Value	$ 53.7	52.6
Excess carrying value of investment over proportionate share of net assets	29.4	29.6
Other Unconsolidated Affiliates [Member]
Schedule of Investments [Line Items]
Carrying Value	$ 1.1	$ 1.4

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

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

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