DEBT - Additional Information (Details)					3 Months Ended			9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 05, 2019 $ / shares	May 09, 2019 $ / shares	Feb. 15, 2019 $ / shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 $ / shares	Sep. 30, 2017 $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 $ / shares	Oct. 01, 2019 USD ($)
Debt Disclosure [Line Items]
Reclassification to Income Statement (less than)					$ 1,000,000
Dividend per share (in usd per share) | $ / shares		$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.40		$ 1.35	$ 1.20
Debt instrument, convertible, remaining discount amortization period	3 years
IAC Notes | Senior Notes
Debt Disclosure [Line Items]
Debt, stated interest rate	5.625%				5.625%			5.625%
Exchange Notes, net | Senior Notes
Debt Disclosure [Line Items]
Debt, stated interest rate	5.625%				5.625%			5.625%
Senior Unsecured Notes | Senior Notes
Debt Disclosure [Line Items]
Principal amount	$ 750,000,000				$ 750,000,000			$ 750,000,000
Debt, stated interest rate	6.50%				6.50%			6.50%
Convertible Notes | Convertible Notes
Debt Disclosure [Line Items]
Principal amount	$ 230,000,000				$ 230,000,000			$ 230,000,000
Debt, stated interest rate	1.50%				1.50%			1.50%
Conversion ratio					0.0000067887		0.0000067482
Debt instrument, convertible, conversion price (in usd per share) | $ / shares	$ 147.30				$ 147.30		$ 148.19	$ 147.30
Interest rate, effective percentage	4.70%				4.70%			4.70%
Term Loan | Corporate Credit Facility
Debt Disclosure [Line Items]
Credit facility	$ 900,000,000				$ 900,000,000			$ 900,000,000
Revolving corporate credit facility, net | Corporate Credit Facility
Debt Disclosure [Line Items]
Credit facility	600,000,000				600,000,000			600,000,000
Revolving corporate credit facility, net | Letter of Credit | Corporate Credit Facility
Debt Disclosure [Line Items]
Credit facility	$ 75,000,000				$ 75,000,000			$ 75,000,000
Convertible Note Hedges
Debt Disclosure [Line Items]
Option indexed to issuer's equity, indexed shares (in shares) | shares							1,550,000
Convertible note hedges exercised (in shares) | shares	0				0			0
Private Warrants
Debt Disclosure [Line Items]
Number of securities called by warrants (in shares) | shares							1,550,000
Number of warrants exercised (in shares) | shares	0				0			0
Exercise price of warrants (in usd per share) | $ / shares	$ 175.63				$ 175.63		$ 176.68	$ 175.63
Minimum | Revolving corporate credit facility, net | Corporate Credit Facility
Debt Disclosure [Line Items]
Basis spread on variable rate								0.50%
Commitment fee percentage								0.20%
Maximum | Revolving corporate credit facility, net | Corporate Credit Facility
Debt Disclosure [Line Items]
Basis spread on variable rate								2.75%
Commitment fee percentage								0.40%
London Interbank Offered Rate (LIBOR) | Term Loan | Corporate Credit Facility
Debt Disclosure [Line Items]
Basis spread on variable rate								2.25%
Interest Rate Swap, September 2023
Debt Disclosure [Line Items]
Derivative, Notional Amount	$ 250,000,000				$ 250,000,000			$ 250,000,000
Derivative, fixed interest rate	2.9625%				2.9625%			2.9625%
Interest Rate Swap, April 2024
Debt Disclosure [Line Items]
Derivative, Notional Amount	$ 200,000,000				$ 200,000,000			$ 200,000,000
Derivative, fixed interest rate	2.248%				2.248%			2.248%
Interest Rate Contract
Debt Disclosure [Line Items]
Derivative, Notional Amount	$ 100,000,000				$ 100,000,000			$ 100,000,000
Cap strike rate	2.50%				2.50%			2.50%
Floor strike rate	1.881%				1.881%			1.881%
Subsequent Event | 2028 Notes | Senior Notes
Debt Disclosure [Line Items]
Principal amount										$ 350,000,000
Debt, stated interest rate										4.75%