SUPPLEMENTAL GUARANTOR INFORMATION - Income Statement (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 1,082			$ 750			$ 3,210	$ 1,916
Expenses	(1,012)			(698)			(2,906)	(1,762)
(Losses) gains and other (expense) income, net	(5)			2			5	(4)
Interest expense	(31)			(14)			(100)	(23)
ILG acquisition-related costs	(32)			(78)			(94)	(98)
Other	1			0			1	(3)
Benefit (provision) for income taxes	(10)			2			(50)	(15)
Equity In Net Income of Subsidiaries	0			0			0	0
Net (loss) income	(7)	$ 49	$ 24	(36)	$ 11	$ 36	66	11
Net income attributable to noncontrolling interests	(2)			0			(2)	0
Net (loss) income attributable to common shareholders	(9)			(36)			64	11
Reportable Legal Entities | MVWC
Condensed Financial Statements, Captions [Line Items]
Revenues	0			0			0	0
Expenses	(7)			(1)			(16)	(6)
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	(3)			(3)			(8)	(8)
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	3			0			7	4
Equity In Net Income of Subsidiaries	(2)			(32)			81	21
Net (loss) income	(9)			(36)			64	11
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	(9)			(36)			64	11
Senior MVW Notes | Reportable Legal Entities | Guarantors
Condensed Financial Statements, Captions [Line Items]
Revenues	575			408			1,981	991
Expenses	(518)			(396)			(1,732)	(901)
(Losses) gains and other (expense) income, net	1			1			0	1
Interest expense	2			(1)			(4)	(3)
ILG acquisition-related costs	(3)			(18)			(17)	(17)
Other	0						0	(3)
Benefit (provision) for income taxes	(4)			2			(74)	(19)
Equity In Net Income of Subsidiaries	0			0			0	0
Net (loss) income	53			(4)			154	49
Net income attributable to noncontrolling interests	(1)			0			(1)	0
Net (loss) income attributable to common shareholders	52			(4)			153	49
Senior MVW Notes | Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues	316			148			697	366
Expenses	(257)			(112)			(545)	(300)
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	4			0			0	0
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	(44)			(8)			(58)	(27)
Equity In Net Income of Subsidiaries	0			0			0	0
Net (loss) income	19			28			94	39
Net income attributable to noncontrolling interests	(1)			0			(1)	0
Net (loss) income attributable to common shareholders	18			28			93	39
Senior MVW Notes | Total Eliminations
Condensed Financial Statements, Captions [Line Items]
Revenues	0			0			(9)	0
Expenses	0			0			9	0
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	0			0			0	0
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	0			0			0	0
Equity In Net Income of Subsidiaries	(56)			(11)			(316)	(153)
Net (loss) income	(56)			(11)			(316)	(153)
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	(56)			(11)			(316)	(153)
Senior MVW Notes | MORI | Reportable Legal Entities | Interval Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Revenues	191			194			541	559
Expenses	(230)			(185)			(622)	(551)
(Losses) gains and other (expense) income, net	(6)			1			5	(5)
Interest expense	(34)			(10)			(88)	(12)
ILG acquisition-related costs	(29)			(60)			(77)	(81)
Other	1						1	0
Benefit (provision) for income taxes	35			7			75	26
Equity In Net Income of Subsidiaries	27			60			142	170
Net (loss) income	(45)			7			(23)	106
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	(45)			7			(23)	106
Senior MVW Notes | ILG | Reportable Legal Entities | Interval Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Revenues	0			0			0	0
Expenses	0			(4)			0	(4)
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	0			0			0	0
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	0			1			0	1
Equity In Net Income of Subsidiaries	31			(17)			93	(38)
Net (loss) income	31			(20)			93	(41)
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	31			(20)			93	(41)
IAC Notes
Condensed Financial Statements, Captions [Line Items]
Revenues	1,082			750			3,210	1,916
Expenses	(1,012)			(698)			(2,906)	(1,762)
(Losses) gains and other (expense) income, net	(5)			2			5	(4)
Interest expense	(31)			(14)			(100)	(23)
ILG acquisition-related costs	(32)			(78)			(94)	(98)
Other	1						1	(3)
Benefit (provision) for income taxes	(10)			2			(50)	(15)
Equity In Net Income of Subsidiaries	0			0			0	0
Net (loss) income	(7)			(36)			66	11
Net income attributable to noncontrolling interests	(2)			0			(2)	0
Net (loss) income attributable to common shareholders	(9)			(36)			64	11
IAC Notes | Reportable Legal Entities | MVWC
Condensed Financial Statements, Captions [Line Items]
Revenues	0			0			0	0
Expenses	(7)			(1)			(16)	(6)
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	(3)			(3)			(8)	(8)
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	3			0			7	4
Equity In Net Income of Subsidiaries	(2)			(32)			81	21
Net (loss) income	(9)			(36)			64	11
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	(9)			(36)			64	11
IAC Notes | Reportable Legal Entities | Interval Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Revenues	0			0			0	0
Expenses	0			0			0	0
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	(1)			(1)			(4)	(1)
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	1			0			2	0
Equity In Net Income of Subsidiaries	31			(16)			95	(37)
Net (loss) income	31			(17)			93	(38)
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	31			(17)			93	(38)
IAC Notes | Reportable Legal Entities | Guarantors
Condensed Financial Statements, Captions [Line Items]
Revenues	286			114			1,083	114
Expenses	(255)			(125)			(970)	(125)
(Losses) gains and other (expense) income, net	0			1			0	1
Interest expense	0			0			(3)	0
ILG acquisition-related costs	(2)			(18)			(16)	(17)
Other	0						0	0
Benefit (provision) for income taxes	(18)			5			(40)	8
Equity In Net Income of Subsidiaries	31			(17)			93	(38)
Net (loss) income	42			(40)			147	(57)
Net income attributable to noncontrolling interests	(1)			0			(1)	0
Net (loss) income attributable to common shareholders	41			(40)			146	(57)
IAC Notes | Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues	796			636			2,136	1,802
Expenses	(750)			(572)			(1,929)	(1,631)
(Losses) gains and other (expense) income, net	(5)			1			5	(5)
Interest expense	(27)			(10)			(85)	(14)
ILG acquisition-related costs	(30)			(60)			(78)	(81)
Other	1						1	(3)
Benefit (provision) for income taxes	4			(3)			(19)	(27)
Equity In Net Income of Subsidiaries	0			0			0	0
Net (loss) income	(11)			(8)			31	41
Net income attributable to noncontrolling interests	(1)			0			(1)	0
Net (loss) income attributable to common shareholders	(12)			(8)			30	41
IAC Notes | Total Eliminations
Condensed Financial Statements, Captions [Line Items]
Revenues	0			0			(9)	0
Expenses	0			0			9	0
(Losses) gains and other (expense) income, net	0			0			0	0
Interest expense	0			0			0	0
ILG acquisition-related costs	0			0			0	0
Other	0						0	0
Benefit (provision) for income taxes	0			0			0	0
Equity In Net Income of Subsidiaries	(60)			65			(269)	54
Net (loss) income	(60)			65			(269)	54
Net income attributable to noncontrolling interests	0			0			0	0
Net (loss) income attributable to common shareholders	$ (60)			$ 65			$ (269)	$ 54