STOCKHOLDERS’ EQUITY - Narrative (Detail)				1 Months Ended		3 Months Ended	9 Months Ended
	Jan. 17, 2018 USD ($) shares	Jan. 17, 2018 shares	Jan. 08, 2018 USD ($) shares	Oct. 31, 2018 USD ($) shares	Jan. 31, 2018 shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2018 USD ($) vote $ / shares	Sep. 30, 2017 USD ($) shares	Oct. 26, 2018 $ / shares	Jan. 03, 2018 USD ($)	Dec. 31, 2017 $ / shares
Class of Stock [Line Items]
Repurchase of common stock (in shares) | shares						195,824		195,824
Authorized amount for Stock Repurchase Program | $										$ 200,000,000
Additional common stock repurchased | $	$ 101,800,000		$ 100,000,000			$ 4,100,000		$ 4,100,000
Remaining amount authorized for repurchase | $							$ 95,900,000
Class A Common Stock
Class of Stock [Line Items]
Voting rights per share | vote							1
Common stock, par value (usd per share) | $ / shares							$ 0.00001				$ 0.00001
Class B Common Stock
Class of Stock [Line Items]
Voting rights per share | vote							1
Repurchase of common stock (in shares) | shares	3,800,000	7,600,000	3,800,000		7,600,000
Common stock, par value (usd per share) | $ / shares							$ 0.00001				$ 0.00001
Subsequent Event
Class of Stock [Line Items]
Repurchase of common stock (in shares) | shares				3,000,000
Additional common stock repurchased | $				$ 48,700,000
Subsequent Event | Class A Common Stock
Class of Stock [Line Items]
Common stock, par value (usd per share) | $ / shares									$ 0.00001
Subsequent Event | Class B Common Stock
Class of Stock [Line Items]
Common stock, par value (usd per share) | $ / shares									$ 0.00001