RETIREMENT BENEFIT PLANS - Benefit obligation and plan assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in projected benefit obligation:
Delphi Technologies acquisition	$ 75
Change in plan assets:
Delphi Technologies acquisition	75
Funded status	(477)	$ (208)
Amounts in the Consolidated Balance Sheets consist of:
Non-current liabilities	(576)	(306)
Other postretirement employee benefits
Change in projected benefit obligation:
Projected benefit obligation, January 1	81	87
Service cost	0	0	$ 0
Interest cost	2	3	3
Plan amendments	(12)	0
Settlement and curtailment	0	0
Actuarial (gain) loss	1	3
Currency translation	0	0
Benefits paid	(8)	(12)
Projected benefit obligation, December 31	65	81	87
Change in plan assets:
Funded status	(65)	(81)
Amounts in the Consolidated Balance Sheets consist of:
Non-current assets	0	0
Current liabilities	(9)	(10)
Non-current liabilities	(56)	(71)
Net amount	(65)	(81)
Amounts in accumulated other comprehensive loss consist of:
Net actuarial loss	16	16
Net prior service (credit) cost	(16)	(8)
Net amount	0	8
Other postretirement employee benefits | Change In Projected Benefit Obligation
Change in projected benefit obligation:
Delphi Technologies acquisition	1	0
Change in plan assets:
Delphi Technologies acquisition	1	0
United States
Change in plan assets:
Funded status	(15)	(22)
United States | Pension benefits
Change in projected benefit obligation:
Projected benefit obligation, January 1	198	253
Service cost	0	0	0
Interest cost	5	8	9
Plan amendments	0	0
Settlement and curtailment		(65)
Actuarial (gain) loss	14	17
Currency translation	0	0
Benefits paid	(15)	(15)
Projected benefit obligation, December 31	202	198	253
Change in plan assets:
Fair value of plan assets, January 1	176	216
Actual return on plan assets	16	29
Employer contribution	10	10
Settlements	0	(65)
Currency translation	0	0
Benefits paid	(15)	(14)
Fair value of plan assets, December 31	187	176	216
Funded status	(15)	(22)
Amounts in the Consolidated Balance Sheets consist of:
Non-current assets	0	0
Current liabilities	(1)	(1)
Non-current liabilities	(14)	(21)
Net amount	(15)	(22)
Amounts in accumulated other comprehensive loss consist of:
Net actuarial loss	94	82
Net prior service (credit) cost	(4)	(5)
Net amount	90	77
Total accumulated benefit obligation for all plans	202	198
United States | Pension benefits | Change In Projected Benefit Obligation
Change in projected benefit obligation:
Delphi Technologies acquisition	0	0
Change in plan assets:
Delphi Technologies acquisition	0	0
United States | Pension benefits | Change In Plan Assets
Change in projected benefit obligation:
Delphi Technologies acquisition	0	0
Change in plan assets:
Delphi Technologies acquisition	0	0
Non-U.S. | Pension benefits
Change in projected benefit obligation:
Projected benefit obligation, January 1	695	612
Service cost	21	18	18
Interest cost	16	12	12
Plan amendments	0	0
Settlement and curtailment	(19)	(5)
Actuarial (gain) loss	161	75
Currency translation	147	(1)
Benefits paid	(36)	(16)
Projected benefit obligation, December 31	2,527	695	612
Change in plan assets:
Fair value of plan assets, January 1	505	438
Actual return on plan assets	83	68
Employer contribution	164	16
Settlements	(18)	(5)
Currency translation	115	4
Benefits paid	(36)	(16)
Fair value of plan assets, December 31	2,041	505	$ 438
Funded status	(486)	(190)
Amounts in the Consolidated Balance Sheets consist of:
Non-current assets	26	28
Current liabilities	(6)	(4)
Non-current liabilities	(506)	(214)
Net amount	(486)	(190)
Amounts in accumulated other comprehensive loss consist of:
Net actuarial loss	330	211
Net prior service (credit) cost	2	2
Net amount	332	213
Total accumulated benefit obligation for all plans	2,471	660
Non-U.S. | Pension benefits | Change In Projected Benefit Obligation
Change in projected benefit obligation:
Delphi Technologies acquisition	1,542	0
Change in plan assets:
Delphi Technologies acquisition	1,542	0
Non-U.S. | Pension benefits | Change In Plan Assets
Change in projected benefit obligation:
Delphi Technologies acquisition	1,228	0
Change in plan assets:
Delphi Technologies acquisition	$ 1,228	$ 0