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FAIR VALUE OF FINANCIAL INSTRUMENTS - Summary of Carrying And Fair Value Of Non-Variable Interest Rate Debt (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2021	Feb. 28, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit, maximum borrowing capacity				$ 300
Carrying Value	$ 2,756	$ 2,356
Term loan facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	2,037
Term loan facility \| 2019 Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	330	330
Term loan facility \| 2021 Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit, maximum borrowing capacity	300
Carrying Value	1,707	1,407
$4.125% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 337	$ 337
$4.125% Senior Notes \| APi Group DE, Inc
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit facility, interest rate	4.125%	4.125%	4.125%
$4.750% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 277	$ 277
$4.750% Senior Notes \| APi Group DE, Inc
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit facility, interest rate	4.75%	4.75%	4.75%
Level 2 \| 2019 Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 330	$ 330
Fair Value	330	331
Level 2 \| 2021 Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,707	1,407
Fair Value	1,711	1,407
Level 2 \| Fixed Income Interest Rate \| Senior Notes \| $4.125% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	337	337
Fair Value	302	305
Level 2 \| Fixed Income Interest Rate \| Senior Notes \| $4.750% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	277	277
Fair Value	$ 254	$ 257