SHAREHOLDERS' EQUITY (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 vote shares	Dec. 31, 2016 shares
Common Stock
Class of Stock [Line Items]
Votes per each share of stock | vote	1
Common stock outstanding (shares)	62,818	0
Common stock reserved	80,000
Class B Convertible Common Stock
Class of Stock [Line Items]
Votes per each share of stock | vote	10
Common stock outstanding (shares)	415,186	0
IAC | Class B Convertible Common Stock
Class of Stock [Line Items]
Common stock outstanding (shares)	415,200
Ownership interest (as a percent)	86.90%
Common stock, voting rights	98.50%