Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets:
Settlement assets	$ 3,648.3	$ 3,687.0
Derivatives	12.4	10.8
Liabilities:
Derivatives	7.0	17.4
Recurring
Assets:
Derivatives	12.4	10.8
Total assets	1,460.6	1,480.8
Liabilities:
Derivatives	7.0	17.4
Total liabilities	7.0	17.4
Recurring \| Money market funds
Assets:
Settlement assets	11.4	11.8
Recurring \| State and municipal debt securities
Assets:
Settlement assets	1,035.0	1,011.4
Recurring \| Asset-backed securities
Assets:
Settlement assets	261.7	195.7
Recurring \| Corporate debt securities
Assets:
Settlement assets	83.4	152.2
Recurring \| State and municipal variable-rate demand notes
Assets:
Settlement assets	47.7	86.8
Recurring \| United States government agency mortgage-backed securities
Assets:
Settlement assets	9.0	12.1
Recurring \| Level 1
Assets:
Total assets	11.4	11.8
Recurring \| Level 1 \| Money market funds
Assets:
Settlement assets	11.4	11.8
Recurring \| Level 2
Assets:
Derivatives	12.4	10.8
Total assets	1,449.2	1,469.0
Liabilities:
Derivatives	7.0	17.4
Total liabilities	7.0	17.4
Recurring \| Level 2 \| State and municipal debt securities
Assets:
Settlement assets	1,035.0	1,011.4
Recurring \| Level 2 \| Asset-backed securities
Assets:
Settlement assets	261.7	195.7
Recurring \| Level 2 \| Corporate debt securities
Assets:
Settlement assets	83.4	152.2
Recurring \| Level 2 \| State and municipal variable-rate demand notes
Assets:
Settlement assets	47.7	86.8
Recurring \| Level 2 \| United States government agency mortgage-backed securities
Assets:
Settlement assets	$ 9.0	$ 12.1

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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