Cash, Cash Equivalents and Investments - Unrestricted and Restricted - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 235	$ 612
Investments	154	135
Total restricted cash, cash equivalents and investments	1,216	1,195
Investments, noncurrent	165	168
Restricted cash, cash equivalents and investments, noncurrent	163	166
Total cash equivalents and investments and restricted cash equivalents and investments	1,933	2,276
Cash and cash equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	235	612
Investments	0	0
Total restricted cash, cash equivalents and investments	1,114	1,097
Investments, noncurrent	0	0
Total cash equivalents and investments and restricted cash equivalents and investments	1,386	1,738
Available-for-sale marketable securities
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	0	0
Investments	154	135
Total restricted cash, cash equivalents and investments	102	98
Investments, noncurrent	165	168
Total cash equivalents and investments and restricted cash equivalents and investments	547	538
Payroll funds collected
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	1,031	1,012
Payroll funds collected \| Cash and cash equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	1,031	1,012
Payroll funds collected \| Available-for-sale marketable securities
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	0	0
Collateral for health benefits claims
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	131	123
Collateral for health benefits claims \| Cash and cash equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	29	25
Collateral for health benefits claims \| Available-for-sale marketable securities
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	102	98
Collateral for workers' compensation claims
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	51	58
Restricted cash, cash equivalents and investments, noncurrent	159	166
Collateral for workers' compensation claims \| Cash and cash equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	51	58
Restricted cash, cash equivalents and investments, noncurrent	33	29
Collateral for workers' compensation claims \| Available-for-sale marketable securities
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	0	0
Restricted cash, cash equivalents and investments, noncurrent	126	137
Other security deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	3	2
Restricted cash, cash equivalents and investments, noncurrent	4	0
Other security deposits \| Cash and cash equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	3	2
Restricted cash, cash equivalents and investments, noncurrent	4	0
Other security deposits \| Available-for-sale marketable securities
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash, cash equivalents and investments	0	0
Restricted cash, cash equivalents and investments, noncurrent	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as noncurrent.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes 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.

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Cash and investments whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

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The current cash, cash equivalents and investments that are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes current cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal.

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The noncurrent cash, cash equivalents and investments that is restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits classified as long-term; that is not expected to be released from such existing restrictions within one year of the balance sheet date or operating cycle, whichever is longer. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes noncurrent cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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