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Other Balance Sheet Information (Details) - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023 | Jun. 30, 2023 | Dec. 31, 2022
--- | --- | --- | --- | ---
Cash and Cash Equivalents [Line Items] |  |  |  |
Overnight Holdings | $ 520 | $ 611 |  |
Short-term Investments | 174 | 135 |  |
Cash | 14 | 27 |  |
Drafts Payable | (16) | (64) |  |
Cash, Cash Equivalents, and Short-term Investments | 692 | 709 |  |
Payroll Withholdings Included in Cash Balance | 459 | 510 |  |
Client Prepayments Included in Cash Balance | (22) | (28) |  |
Cash and cash equivalents | 676 | 693 | $ 580 | $ 733
Restricted cash | 64 | 57 | 48 | 50
Funds Held for Clients | 38 | 87 | 34 | 35
Deposits workers compensation | 170 | 198 | 181 | 196
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Total | 948 | 1,035 | 843 | 1,014
ERCFundsReceivedIncludedInCashBalance | 97 |  |  |
Supplemental cash flow information: |  |  |  |
Restricted cash | 64 | 57 | 48 | 50
Funds Held for Clients | 38 | 87 | 34 | 35
Deposits workers compensation | 170 | 198 | 181 | 196
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Total | 948 | 1,035 | $ 843 | $ 1,014
ERCFundsReceivedIncludedInCashBalance | 97 |  |  |
Money Market Funds [Member] |  |  |  |
Cash and Cash Equivalents [Line Items] |  |  |  |
Overnight Holdings | 0 | 0 |  |
Short-term Investments | 16 | 16 |  |
Cash | 0 | 0 |  |
Drafts Payable | 0 | 0 |  |
Cash, Cash Equivalents, and Short-term Investments | 16 | 16 |  |
Cash and Cash Equivalents [Member] |  |  |  |
Cash and Cash Equivalents [Line Items] |  |  |  |
Overnight Holdings | 520 | 611 |  |
Short-term Investments | 158 | 119 |  |
Cash | 14 | 27 |  |
Drafts Payable | (16) | (64) |  |
Cash, Cash Equivalents, and Short-term Investments | $ 676 | $ 693 |  |

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- Definition Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(9)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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