CASH, CASH EQUIVALENTS AND INVESTMENTS - UNRESTRICTED AND RESTRICTED (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 287	$ 354
Investments	65	76
Restricted cash, cash equivalents and investments	1,269	1,263
Investments, noncurrent	143	151
Restricted cash, cash equivalents and investments, noncurrent	158	153
Total	1,922	1,997
Payroll funds collected
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	1,067	1,062
Collateral for health benefits claims
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	144	139
Collateral for workers' compensation claims
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	56	58
Restricted cash, cash equivalents and investments, noncurrent	158	150
Other security deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	2	4
Restricted cash, cash equivalents and investments, noncurrent	0	3
Cash and cash equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	287	354
Investments	0	0
Restricted cash, cash equivalents and investments	1,154	1,153
Investments, noncurrent	0	0
Total	1,466	1,537
Cash and cash equivalents \| Payroll funds collected
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	1,067	1,062
Cash and cash equivalents \| Collateral for health benefits claims
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	31	29
Cash and cash equivalents \| Collateral for workers' compensation claims
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	54	58
Restricted cash, cash equivalents and investments, noncurrent	25	27
Cash and cash equivalents \| Other security deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	2	4
Restricted cash, cash equivalents and investments, noncurrent	0	3
Available-for-sale marketable securities
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	0	0
Investments	65	76
Restricted cash, cash equivalents and investments	115	110
Investments, noncurrent	143	151
Total	456	460
Available-for-sale marketable securities \| Payroll funds collected
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	0	0
Available-for-sale marketable securities \| Collateral for health benefits claims
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	113	110
Available-for-sale marketable securities \| Collateral for workers' compensation claims
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash, cash equivalents and investments	2	0
Restricted cash, cash equivalents and investments, noncurrent	133	123
Available-for-sale marketable securities \| Other security deposits
Restricted Cash and Cash Equivalents Items [Line Items]
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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