INVESTMENTS - Schedule of Financial Instruments by Significant Categories and Fair Value Measurement on a Recurring Basis (Details) - Fair Value Measurement on a Recurring Basis - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities
Cash equivalents:	$ 171	$ 571
Amortized Cost	205	230
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	(3)
Fair Value	206	227
Cash and Cash Equivalents
Debt Securities
Cash equivalents:	31	257
Fair Value	0	0
Investments
Debt Securities
Cash equivalents:	0	0
Fair Value	0	0
Restricted Cash, Cash Equivalents and Investments
Debt Securities
Cash equivalents:	140	314
Fair Value	206	227
Corporate bonds \| Level 2
Debt Securities
Amortized Cost	34	35
Gross Unrealized Gains	0
Gross Unrealized Losses	0	0
Fair Value	34	35
Corporate bonds \| Level 2 \| Cash and Cash Equivalents
Debt Securities
Fair Value	0	0
Corporate bonds \| Level 2 \| Investments
Debt Securities
Fair Value	0
Corporate bonds \| Level 2 \| Restricted Cash, Cash Equivalents and Investments
Debt Securities
Fair Value	34	35
Agency securities \| Level 2
Debt Securities
Amortized Cost	13	18
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Fair Value	13	17
Agency securities \| Level 2 \| Cash and Cash Equivalents
Debt Securities
Fair Value	0	0
Agency securities \| Level 2 \| Investments
Debt Securities
Fair Value	0
Agency securities \| Level 2 \| Restricted Cash, Cash Equivalents and Investments
Debt Securities
Fair Value	13	17
U.S. treasuries \| Level 2
Debt Securities
Amortized Cost	158	176
Gross Unrealized Gains	1
Gross Unrealized Losses	0	(2)
Fair Value	159	174
U.S. treasuries \| Level 2 \| Cash and Cash Equivalents
Debt Securities
Fair Value	0	0
U.S. treasuries \| Level 2 \| Investments
Debt Securities
Fair Value	0
U.S. treasuries \| Level 2 \| Restricted Cash, Cash Equivalents and Investments
Debt Securities
Fair Value	159	174
Certificate of deposit \| Level 2
Debt Securities
Amortized Cost		1
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		1
Certificate of deposit \| Level 2 \| Cash and Cash Equivalents
Debt Securities
Fair Value		0
Certificate of deposit \| Level 2 \| Investments
Debt Securities
Fair Value		0
Certificate of deposit \| Level 2 \| Restricted Cash, Cash Equivalents and Investments
Debt Securities
Fair Value		1
Money market mutual funds \| Level 1
Debt Securities
Cash equivalents:	164	570
Money market mutual funds \| Level 1 \| Cash and Cash Equivalents
Debt Securities
Cash equivalents:	31	257
Money market mutual funds \| Level 1 \| Investments
Debt Securities
Cash equivalents:	0	0
Money market mutual funds \| Level 1 \| Restricted Cash, Cash Equivalents and Investments
Debt Securities
Cash equivalents:	133	313
U.S. treasuries \| Level 2
Debt Securities
Cash equivalents:	7	1
U.S. treasuries \| Level 2 \| Cash and Cash Equivalents
Debt Securities
Cash equivalents:	0	0
U.S. treasuries \| Level 2 \| Investments
Debt Securities
Cash equivalents:	0	0
U.S. treasuries \| Level 2 \| Restricted Cash, Cash Equivalents and Investments
Debt Securities
Cash equivalents:	$ 7	$ 1

TRINET GROUP, INC. 10-Q